Book of Abstracts

Title Author Session Abstract Affiliation Scheduled Date (Time)
Estimating ocean net primary productivity from daily cycles of carbon biomass measured by profiling floats 1Adam Stoer, 1Katja Fennel Poster Session 2 The dependence of net primary productivity (NPP), a central metric in ecology and biogeochemistry, on sunlight drives daily cycles in carbon biomass in the ocean's euphotic zone. In this study, we infer NPP from the daily cycle of biomass. These estimates were extracted from bio-optical measurements collected by an array of robotic profilers distributed across temperate and polar regions of the southern hemisphere. Our estimates of NPP in these regions are within the range of different satellite-based models. We argue that this approach could provide complementary, ground-truthed information for satellite-based tools, which could be used to assess basin-scale trends in primary productivity in the future. 1Dalhousie University, Canada 2023/08/10 (17:00-18:30)
Spatio-temporal assessment of the impacts of the trends in physical and biogeochemical parameters on the primary production of the Gulf of Guinea 1Adeola Michael Dahunsi, 2Tolulope S. Oyikeke, 3Mujeeb A Abdulfatai, 4Lateef A. Afolabi Poster Session 2 This study applied ocean models data from Copernicus Marine Environment Monitoring Service (CMEMS) in assessing the impacts of the trends in key ocean parameters on the primary production of the Gulf of Guinea (GoG). Trend analyses, from 1993-2020, were done using linear regression and Mann-Kendall significance test methods to ascertain inter-annual and inter-seasonal variations and check the significance of the trends, respectively. Results affirm that temperature, salinity, nutrients, and oxygen play significant roles in the primary production of the GoG. Also, parameters such as temperature, salinity, chlorophyll-A, net primary production, phosphate, and dissolved oxygen have been experiencing increases between the study duration while silicate and nitrate have been declining in the GoG. However, there are regions and years with contrary values to the average trends. The varying level of significance of the trend showed that the impacts of the climate on the primary production of the GoG vary basin-wide. 1International Chair in Mathematical Physics and Applications (ICMPA), University of Abomey-Calavi, Abomey-Calavi, Benin Republic; 2Department of Climate Change and Marine Sciences, Universidade Técnica do Atlântico (UTA) - ISECMAR. Cabo Verde; 3Wegener-Institute Helmholtz Centre for Polar- and Marine Research, Bremerhaven, Germany; 4Department of Fisheries and Aquatic Sciences, University of Cape Coast, Cape Coast, Ghana 2023/08/10 (17:00-18:30)
Investigating the Impact of Climate Change on Phytoplankton Phenology in the Tropical Indian Ocean 1Aditi Modi, 1Roxy Mathew Koll, 2Subimal Ghosh Oral Session 1: Physical and biological interactions The Indian Ocean has experienced the most significant surface warming amongst other tropical ocean basins during the past half-century. Previous studies have investigated the response of the marine ecosystem to ocean warming in the western tropical Indian Ocean and found that there is a reduction in marine primary productivity caused by warming of the ocean surface. The seasonal cycle of phytoplankton is very significant in the tropical Indian Ocean due to the semi-annual reversal of winds at the equator. Climate change is also expected to alter the phenology of phytoplankton through modifications to the underlying physical drivers controlling bloom timing. This variability in the phenology of these phytoplankton blooms will affect the ecosystem dynamics with repercussions for the carbon export production and availability of food at higher trophic levels. This work identifies the main patterns of phytoplankton phenology in the tropical Indian Ocean using a gap-filled remote-sensed ocean color dataset and addresses the phenological shifts of phytoplankton blooms in response to the change in physical variables under a changing climate. 1Indian Institute of Tropical Meteorology, Pune, India; 2IDP in Climate Studies, Indian Institute of Technology Bombay, India 2023/08/09 (11:30-11:45)
Bio-optical properties of dinoflagellate blooms from Todos Santos Bay (Baja California, México) 1Adriana Gonzalez Silvera, 1Mariana Larios-Muñiz, 1Maria Ester Guzman, 1Jorge López-Calderón Oral Session 4: Physiological ecology of marine phytoplankton Todos Santos Bay is located on the northwest coast of Baja California (Mexico) where harmful phytoplankton blooms (HABs) are regularly recorded and associated to dinoflagellates, causing strong economic consequences particularly affecting the development of bivalve mollusk and tuna cultures. From 2017 to 2022, some bio-optical characteristics of eight bloom events were recorded, when chlorophyll-a concentration (Chla) ranged from 6.3 to 36.2 mg/m3 and cell abundance from 142,920 to 717,800 Cel/L. Most events were dominated by Lingulodinium polyedra while the others were characterized by a mixed community of dinoflagellates (e.g. Prorocentrum sp, Gymnodimum sp). The spectral shape of the light absorption coefficient by phytoplankton (aph(l)), colored dissolved organic matter (aCDOM(l)) and detritus plus CDOM (adg(l), between 250 and 700 nm, was examined and compared to a baseline spectrum obtained from a database where no bloom has been detected and Chla is below 2 mg/m3. The aph(l), aCDOM(l) and adg(l) spectra from the stations affected by blooms were characterized by a shoulder around 370 and a steep increase from blue wavelengths to this UV wavelength. To represent this feature and to compare with the baseline spectrum, the spectral slope (S, m-1) between 370 and 412 nm was calculated. Results show the potential of Sdg and SCDOM as indicators of bloom condition, particularly when the bloom is dominated by L. polyedra, what should be a useful tool for the detection of bloom development using satellite images or buoy platforms. 1Universidad Autónoma de Baja California (UABC), Mexico 2023/08/10 (11:30-11:45)
Dissolved oxygen and pH variability within seagrass meadows: mitigators of ocean acidification and potential refugia for CaCO3 dependent organisms? 1Ahmed Mohamed, 1Mark Huxham, 1Karen Diele, 2Marco Fusi Poster Session 2 Increasing atmospheric CO2 concentrations are causing acidification in tandem with warming of the oceans. The pH of ocean surface waters has decreased by 0.1 units since the beginning of the industrial era (IPCC 2013) and is further expected to decrease by ~0.4 by the year 2100. There is a growing concern for the future of calcifying organisms, following long-term changes in ocean pH that result in lower calcium carbonate saturation. Metabolic-intense habitats such as seagrasses, coral reefs and macroalgae can remove significant amounts of dissolved inorganic carbon (DIC) to produce short timescale elevations in mean values of pH and carbonates. Seagrass productivity ranks among the highest in coastal environments and can utilize large amounts of DIC through photosynthetic uptake and therefore temporarily ameliorate low pH and offset ocean acidification, at least at local scales. Here, we investigate the variability of dissolved oxygen (DO) and pH within seagrasses and bare sites. Using in-situ data loggers we recorded physicochemical properties (pH, DO, water temperature, and light) at 15 minutes intervals for 41 days in shallow areas with seagrasses and bare sites (unvegetated plots) in Kenya. We found no differences in mean values for pH (8.0) and DO (6.1 mg/L) between seagrass areas and bare sites. However, bare sites recorded higher pH values (pH of 8.6) compared to seagrasses (8.3), and higher DO values (9.34 mg/L) compared to seagrasses (8.47 mg/L). Both seagrasses and bare areas had similar minimum pH values (7.8) but for DO, bare sites recorded lower values (2.8 mg/L) compared to seagrasses (3.5 mg/L). Statistically, we found significant difference in pH (p-value =7.5e-31) and DO variability (p-value = 2.82e-05) between seagrass and bare sites, but this variability is stronger in bare sites compared to seagrass areas. Our results contradict the hypothesis that seagrasses would have a larger variability in pH/DO and record highest pH/DO values due to primary productivity. These results indicate that seagrass meadows are relatively stable environments and could potentially be useful for marine biodiversity because of high resistance to change. 1Edinburgh Napier University, UK; 2Joint Nature Conservation Committee, UK 2023/08/10 (17:00-18:30)
Seagrass meadows: mitigators of ocean acidification and potential refugia for caco3 dependent organisms? 1Ahmed Mohamed, 1Mark Huxham, 1Karen Diele, 2Marco Fusi Poster Session 1 Anthropogenic climate change poses a mounting threat to human wellbeing and health of the planet. Increasing atmospheric CO2 concentrations are causing acidification in tandem with warming of the oceans. The pH of ocean surface waters has decreased by 0.1 units since the beginning of the industrial era (IPCC 2013) and is further expected to decrease by ~0.4 by the year 2100. There is a growing concern for the future of calcifying organisms, following long-term changes in ocean pH that result in lower calcium carbonate saturation. Metabolic-intense habitats such as seagrasses, coral reefs and macroalgae can remove significant amounts of dissolved inorganic carbon (DIC) to produce short timescale elevations in mean values of pH and carbonates. Seagrass productivity ranks among the highest in coastal environments and can utilize large amounts of DIC through photosynthetic uptake and therefore temporarily ameliorate low pH and offset ocean acidification, at least at local scales. Here, we investigate the role of seagrass in offsetting ocean acidification and providing temporary refugia for calcifying organisms. Coral fragments (Acropora formosa) of ~5 centimeters were grown within seagrasses in Kenya for a period of 8 months. Two field sampling campaigns were conducted to record coral growth and survival. Length, width, and wet weight for each coral fragment were measured and the condition of the fragment recorded as alive, dead, or partially dead/alive as a percentage. Coral fragments in bare sites were ~14 percent heavier and ~79 percent longer, on average, compared to coral fragments within seagrasses. The observed difference in coral growth could be due to competition for nutrients between seagrasses and the zooxanthellae in the corals, shading effect of seagrasses or physical stress (abrasion) on the corals by the seagrass leaves but it is difficult to conclude the reason from this present study. Additionally, we observed lower temperature values for seagrass areas compared to bares sites (difference of 1.5 oC) suggesting that seagrass meadows might play an important role for corals during high heat stress episodes. These results contradict the idea that seagrass meadows could enhance the growth of calcifiers compared to non-vegetated areas. However, because we did not test for resilience or during periods of extreme temperature stress, seagrass might still play an important role in benefitting calcifiers. 1Edinburgh Napier University, UK; 2Joint Nature Conservation Committee, UK 2023/08/09 (17:30-19:00)
Winter variability of Eddy Kinetic Energy in the SE Arabian Sea and its significance on Chl-a concentration 1Ajith Joseph Kochuparampil, 1Ullas M Pillai, 2Roshin P Raj, 3Ola M Johannessen Poster Session 1 Eddy kinetic energy (EKE) is a measure of temporal and spatial variability of ocean mesoscale eddies. This study elucidates the key factors that determine the winter distribution, generation and significance of mesoscale eddies in the south-eastern Arabian sea (SEAS) using satellite observational data from Copernicus Marine service data centre, during the time period 1993-2020. In general eddy kinetic energy is found to be higher during winter. The higher EKE throughout the winter was found to be due to the barotropic instability of the Winter Monsoon Current in the SEAS due to the barotropic instability caused by the strong negative wind stress curl, resulting in the conversion of mean kinetic energy to eddy kinetic energy. The ESA OC-CCI chlorophyll-a data were used to study the influence of EKE on the presence of higher Chlorophyll in the SEAS by using linear regression and correlation analysis. A significant positive correlation between EKE and chlorophyll-a concentration during winter monsoon indicates the significance of eddies in the distribution of surface chlorophyll-a concentration over the SEAS during winter monsoon. 1Nansen Environmental Research Centre(India); 2Nansen Environmental and Remote Sensing Centre, Norwa;, 3Nansen Scientific Society, Norway 2023/08/09 (17:30-19:00)
Derivative based identification of optimal spectral bands for chlorophyll-a algorithm in different water types along Indian coast 1Alakes Samanta, 1Aneesh A Lotliker, 1Sanjiba Kumar Baliarsingh Poster Session 1 In coastal waters, the non-covariance of other optically active substances (OAS) other than Chlorophyll-a (Chl-a), such as coloured dissolved organic matter (CDOM) and total suspended matter (TSM), results in poor performance of the empirical algorithms in retrieving Chl-a from ocean colour data. However, the empirical algorithms can still be improved by specifying the coefficient at the regional level and choosing appropriate bands. The present study characterizes Indian coastal waters into different optical types and identifies suitable bands having the optimal effect of Chl-a using derivative technique applied to 417 in-situ remote sensing reflectance (Rrs) spectra. The Indian coastal waters exhibit four optical types having peak Rrs at 440 nm (Type-1), 486 nm (Type-2), 533 nm (Type-3), and 566 nm (Type-4). The geographical distribution showed that Type-1 water encountered farthest (38 ± 21 km) whereas Type-4 was closest (6 ± 3 km) to the coast indicating the source of OAS is from land discharge and/or coastal processes. The second-order spectral derivatives of Rrs showed 12 common peaks in all four water types, having an optimal impact of Chl-a on Rrs in the presence of other OAS. The maximum band ratio of Rrs at 415, 440, 465, 490, and 530 nm with 550 nm was found to have a better correlation (R2=0.92) with in-situ Chl-a using a fourth-order polynomial fit. This study proposes a new empirical model for Chl-a retrieval from the Indian coastal waters and suggests the inclusion of new bands in future ocean colour satellite sensors. 1Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Government of India, Hyderabad-500090, India 2023/08/09 (17:30-19:00)
Hyperspectral Prisma Data Processing For Water Quality Research And Applications 1Alice Fabbretto, 1Pellegrino A , 1Giardino C, 1Bresciani M, 1Alikas K, 1Braga F, 1Mangano S, 1Ghirardi N, 1Daraio M G, 1Brando V E Poster Session 1 Nowadays, the quality of waterbodies has been seriously threatened due to climate changes: in this context, new generation satellite hyperspectral sensors are contributing to the water resources studies. This work aims to show the main goals achieved by the exploitation of hyperspectral PRISMA data for aquatic ecosystems mapping. The suitability of PRISMA radiance and reflectance products was demonstrated through comparison with reference data: Sentinel-2, Sentinel-3 and in-situ measurements obtained through field campaigns, where reflectance and water quality data are collected simultaneously. In accordance with the state-of-the-art of water constituents’ retrieval algorithms, water quality products were obtained with two approaches: bio-optical modelling inversion techniques (BOMBER tool) and semi-empirical algorithms. Through the BOMBER, we generated water quality products in terms of Chlorophyll-a (Chl-a) and bottom substrate maps. Through the semi-empirical algorithm, we generated Chl-a maps and Total Suspended Matter (TSM). The maps obtained with BOMBER showed an agreement with the reference data in RMSE = 2.02 mgm-3 for Chl-a retrieval and an overall accuracy of 80% for the characterization of the bottom substrate. The maps obtained with the semi-empirical algorithms have shown the following results: RMSE = 3.05 mgm-3 for Chl-a retrieval and RMSE = 1.88 gm-3 for TSM retrieval. Generally, PRISMA-derived products overestimate reference data, this is likely consistent with some issues in the atmospheric correction of satellite data. Finally, despite the need of more in-depth analysis, PRISMA data are providing valuable information for aquatic ecosystems and - in synergy with multispectral missions - are offering support to water management activities. 1National Research Council of Italy, Italy 2023/08/09 (17:30-19:00)
Analytical derivation of water clarity in optically complex waters 1Amanda de Liz Arcari, 1Juliana Tavora, 1,2Daphne van der Wal, Mhd, 1Suhyb Salama Poster Session 1 Water clarity relates to the combined effects of water constituents that attenuate light, such as suspended material, phytoplankton, and coloured dissolved organic matter. Besides being strongly related to primary productivity and trophic state, this ensemble indicator also influences water-atmosphere heat transfer. Water clarity, expressed as the diffuse attenuation coefficient of photosynthetically active radiation (kd(PAR)), is therefore a key input for lake models in numerical weather prediction. Current satellite sensors offer the possibility of capturing kd(PAR) spatial-temporal variability in waterbodies, which is critical to advance understanding of the nexus between water quality and climate. In this study, we introduce a fully analytical model to derive kd(PAR) from Sentinel-2 imagery based on the solution of the two-stream radiative transfer equations. The analytical solution implies the model does not rely on empirical relationships and regional tuning. It thus provides a general approach to derive kd(PAR) in diverse optical complexities. The applicability of the model to Case-2 waters is demonstrated in Conceição Lagoon, Southern Brazil. A time series of kd(PAR) maps was constructed from Sentinel-2 images captured between 2019 and 2021. Analysis allowed the identification of a consistent spatial pattern and the detection of temporal anomalies. Hotspots of reduced water clarity are seen in the lagoon’s margins and where a cyclonic gyre favours resuspension. A trend of decreasing water clarity is also seen in areas of intensifying anthropic pressure. The model can therefore provide valuable information to further investigate the feedback mechanism between water quality and the thermal balance of aquatic systems. 1Faculty of Geo-Information Science and Earth Observation (ITC) University of Twente, Netherlands; 2Royal Netherlands Institute for Sea Research (NIOZ), Netherlands 2023/08/09 (17:30-19:00)
Mapping stress in submerged aquatic vegetation using advanced remote sensing techniques 1Amritha Nair, 1Fleur Visser Poster Session 1 Inland waters such as streams sustain a rich variety of species and are essentially hotspots for biodiversity. Submerged aquatic vegetation, also known as SAV, forms an important part of ecologically healthy river systems. Direct and indirect human influences, such as climate change are putting stress on aquatic plant communities, ranging from the invasion of non-native species and grazing, to changes in the river flow conditions and temperature. There is a need to monitor SAV, because they are in a state of deterioration and their disappearance will greatly impact river ecosystems. Like terrestrial plants, SAV can show visible signs of stress. However, the techniques used to map terrestrial vegetation from its spectral reflectance, are not easily transferable to a submerged environment. Optical remote sensing techniques are employed to detect the stress from remotely sensed images through multispectral imagery and Structure from Motion photogrammetry. The effect of the overlying water column in the form of refraction, attenuation of visible and NIR bands in water, as well as highly moving targets, are key challenges that arise when remotely mapping SAV. This study looks into the possibility of mapping the changes in spectral signatures from SAV and their response to certain stresses. In my proposed presentation, I will be discussing the methods used to detect stress in SAV and share the results obtained so far from the analysis. 1University of Worcester, UK 2023/08/09 (17:30-19:00)
Assessing Phytoplankton Bloom Phenology in the Southwest Atlantic Using Ocean Colour Remote Sensing 1,2Ana Ines Dogliotti, 2,3Vivian Lutz, 2,3Moira Luz Clara , 3Reinaldo A. Maenza, 4Robert Frouin Poster Session 1 ocean both in terms of phytoplankton biomass but also for the great abundance of economically important fish and mollusc species, sea birds and marine mammals. It is a highly dynamic and heterogeneous region characterized by the Brazil-Malvinas Confluence zone, the wide and flat Argentinean shelf, and the presence of several oceanographic fronts which have been associated with enhanced chlorophyll-a (Chl-a) concentration and with intense CO2 uptake from spring through autumn. In this study we evaluate phytoplankton phenology patterns over the SWA area during a 22-year period (January 1998 – December 2019) using satellite ocean colour data. First, two datasets, CCI-OC (v6) and GlobColour (v4.2.1), are evaluated using in situ Chl-a measurements available in this region. Then, different phenological indices of the spring bloom are estimated for the whole region. And finally, phytoplankton phenological indices and their interannual variability patterns are described for selected sites. The relative importance of different forcing, that may be subject to variations due to climate change (like the incoming solar irradiance and mixed layer depth), in the variability of the phenological indices (like the initiation of the spring bloom) in the different sites of interest are analyzed. 1Institute of Astronomy & Space Physics (IAFE) CONICET/UBA, Argentina; 2National Scientific and Technical Research Council, Argentina; 3INIDEP Instituto Nacional de Desarrollo Pesquero, Argentina; 4SCRIPPS, Argentina 2023/08/09 (17:30-19:00)
Status of in situ and satellite observations in Latin America 1,2Ana Ines Dogliotti, 1,2Moira Luz Clara Oral Session 2: Marine Optics & Ocean Colour Sustained ocean observations provide crucial data to understand marine ecosystems, help monitoring the impacts of long-term climate change and implement adaptation and mitigation strategies. Effective monitoring of marine ecosystems requires sustained regional networks of physical, biological, and biogeochemical time series observations that integrate shipboard, autonomous, and remote sensing platforms. Sustained and increased high quality observations are needed in all regions of the oceans, however it’s clear that more information has been gathered in the Northern compared to the Southern hemisphere. Even though maintaining sustained ocean time series is challenging all over the world, especially after the pandemic, it’s even more for countries that have limited availability of resources. In spite of this, different efforts have been put into strengthening marine ecological observing capacity in Latin America and fostering global collaboration and networking in order to advance in science and expand and improve measurements. This presentation aims to show the current status of different efforts that are being devoted to enhance ocean observations around Latin America. 1Institute of Astronomy & Space Physics (IAFE) CONICET/UBA, Argentina; 2National Scientific and Technical Research Council, Argentina 2023/08/09 (13:30-14:00)
Microbial pollution in a tropical lake and the incidence of acute diarrheal diseases 1Anas Abdulaziz, 2Shubha Sathyendranath, 3,4Nandini Menon, 5Grinson George, 2Gemma Kulk, 1,6Kiran Krishna, 1Devika Raj, 3Ranith Rajamohananpillai, 3,4Jasmin C Oral Session 5: Water Quality and human health Microbial pathogenic pollution of aquatic systems can lead to outbreaks of water-associated diseases in human populations in the vicinity. Vembanad lake, on the south-west coast of India, was monitored for microbial pollution for one year (2018-19), revealing the widespread presence Escherichia coli, an indicator of faecal pollution. More than 50% of the E. coli was resistant to multiple antibiotics. Increases in the abundance of E. coli and in the incidence of acute diarrhoeal disease (ADD) were recorded during early phase of the 2018 south-west monsoon (June-July). A potential explanation is that the rising ground water mixes with sewage, which then drains into the lake. Paradoxically, during the subsequent floods in August 2018, the number of ADD cases dropped, which could be attributed to the increased flow of water that swept the pathogenic bacteria out into the sea (as suggested by dropping levels of E. coli), and to the increased efforts by various organizations to encourage the affected population to chlorinate and boil water prior to use. On the contrary, during the time of COVID-19-related lockdown in March-May 2021, when many human activities over the lake were suspended, faecal contamination in the lake and incidence of ADD reached minimum values. Results of our study indicate the need to: 1) avoid consumption of lake waters contaminated by faecal pathogens; 2) continue monitoring of lake waters for faecal contamination; 3) prevent discharge of faecal waste into the waters; and 4) reinvent sanitation practices; to achieve the global agenda of eradicating water-associated diseases. 1CSIR-National Institute of Oceanography, Regional Centre, Kochi, India; 2Plymouth Marine Laboratory, Plymouth, Devon, UK; 3Nansen Environmental Research Centre (India), Kochi, 682506, India; 4Trevor Platt Science Foundation, Kochi, 682 018, India; 5ICAR-Central Marine Fisheries Research Institute, Kochi, 682018, India; 6Academy of Scientific and Industrial Research (AcSIR), Ghaziabad, 201002, India 2023/08/10 (14:00-14:15)
Applying mobile crowd sourcing techniques with citizen scientists for identifying water colour trends in Vembanad Lake, India 1Ancy C Stoy, 1A Gopalakrishnan, 1Grinson George, 2Nandini Menon, 1Mini K G, 1Pranav P, 3Shubha Sathyendranath Poster Session 2 The COVID 19 global pandemic has challenged the conventional approaches to research data acquisition using ship-based technologies. Today, the expert-layman divides are eroding. Bridging the gap between scientists and citizens, we are studying the water colour dynamics of the Vembanad Lake by placing citizen science at the fulcrum of data collection. The Forel-Ule (FU) colour index and water quality are closely related. A new understanding of the spatio-temporal variation in the colour and clarity of the Vembanad Lake waters is sought using smart phone images as a research tool. A Mini Secchi Disk (MSD) attached with FU colour scale and a stand-alone mobile application ‘Turbaqua’ assist in achieving our objectives. Colour, an effective measure of water quality is extracted from the digital images using Water COlor from Digital Images (WACODI) algorithm. By using multiple observations, we are able to extract seasonal changes in water colour. In addition, annual trends in water colour of the lake during recent years were constructed using FU colour maps for the Vembanad Lake. Our results show that Vembanad Lake consists mostly of ‘greenish brown to brownish green’ coloured waters, falling between 14 and 17 on the FU colour scale. Democratizing science to include common man in data acquisition, we could have new and dynamic view of the water quality and health status of the lake in a much more affordable way than by conventional means. The study could establish a new approach to water colour monitoring of Vembanad Lake using the participation of citizen scientists. 1ICAR-Central Marine Fisheries Research Institute, Kochi, India; 2Nansen Environmental Research Centre India; 3Plymouth Marine Laboratory UK 2023/08/10 (17:00-18:30)
Evaluating the potential of different orbital sensors to detect algal bloom events 1Andréa de Lima Oliveira, 1Natália Rudorff, 1Gabriel Moiano César, 2Luciane Favareto, 1Milton Kampel Poster Session 1 Harmful algal blooms may cause environmental, public health, and economic damages, and have been reported in worldwide increasing events. The use of orbital sensors to detect and monitor algal bloom in coastal areas is key for automatizing alert systems and reducing costs with in-situ sampling, limited by human and infrastructure resources. However, satellite monitoring is also limited by spatial, spectral, and temporal resolutions. Here we investigate the spectral resolution in the detection of algal bloom events in a coastal region of the southwestern Atlantic Ocean. We used in situ above-water radiometric data collected in different conditions: visually detected algal bloom; non-visual algal bloom but abnormally high chlorophyll-a concentration (>5mg.m-3), and non-algal bloom condition. We tested two algorithms to detect the algal bloom. One based on a simple band ratio (Rrs(688)/Rrs(564)) and the other the normalized difference chlorophyll index (NDCI) (Rrs(709)-Rrs(665))/(Rrs(709)+Rrs(665)). We then compared the results using hyperspectral remote sensing reflectance and simulated bands for different sensors, i.e., MODIS, MERIS, OLCI, OLI, VIIRS, and the OCI (PACE). The results indicated that the NDCI obtained positive values for the “visual bloom” cases for most sensors. However, in the initial stage of the algal bloom (non-visual detection), the band ratio was more effective. Thus, we suggest a combination of algorithms to detect such blooms. OCI was the best to differentiate each case with the highest differences among the calculated index values, followed by MERIS and OLCI, which performed similarly, and MODIS. VIIRS and OLI showed lower capability of bloom detection using these indexes. 1INPE- National Institute for Space Research, Brazil; 2MARE - Marine and Environmental Sciences Centre, Faculdade de Ciências, Universidade de Lisboa, Portugala 2023/08/09 (17:30-19:00)
Biophysical responses to El nino-Southern Oscillation at the South Brazil Bight 1Andréa de Lima Oliveira, 1Natália Rudorff, 2Shubha Sathyendranath, 1Milton Kampel Poster Session 2 El Niño Southern Oscillation (ENSO) is one of the main source of large-scale inter-annual variability in Earth‘s climate. Previous studies have indicated that ENSO is associated with impacts on marine phytoplankton at the global scale but presents greater effects on the tropics and subtropics. In this study, to address the spatial variability of ENSO impacts in the South Brazil Bight (SBB), we analysed the correlation of the Multivariate ENSO Index (MEI v.2) with sea surface temperature (MUR SST), chlorophyll-a concentration (MODIS/Aqua Chla), and micro and nanophytoplankton fraction (Fmn) estimated between 2002-2020. Mean annual anomalies were calculated for the climate index, physical and biological variables, and a correlation analysis and a Student t-test were performed. A significant positive correlation was observed between MEI and SST in much of the study region, except for the northern coastal region off Rio de Janeiro. Significant negative correlations with Chla were observed over the mid- and outer shelf, north of São Paulo and Rio de Janeiro and in areas further offshore. The results indicate that a large part of the variability in SBB is associated with ENSO, especially in SST, except for areas more susceptible to upwelling events, which are influenced by other forcing factors, such as winds, varying over other time scales. Regarding Chla and Fmn, the results indicate that other factors can contribute to modulation of its variability at different scales, demanding further investigation. 1INPE- National Institute for Space Research, Brazil; 2PML - Plymouth Marine Laboratory, UK 2023/08/10 (17:00-18:30)
Pelagic size spectra: history, limitations, and some diverse applications 1Angus Atkinson, 1Axel G Rossberg, 1Ursula Gaedke, 1Gary Sprules, 1Stratos Batziakas, 1Ryan F Heneghan, 1Maria Grigoratou, 1Elaine Fileman, 1Katrin Schmidt, 1Constantin Frangoulis, 1Martin Lilley Oral Session 6: Size and ecosystem structure of aquatic communities Body size is a key trait that modulates a plethora of processes within aquatic ecosystems. In a remarkable law of nature not yet fully understood, the normalised biomass size spectrum shows an uncanny degree of linearity across a huge range in size from bacteria to whales. The rate of attenuation of biomass within progressively larger organisms (i.e. the steepness of size-spectrum slopes) neatly quantifies an emergent property of complex ecosystems, measuring how inefficiently energy is transmitted up to larger organisms. This inefficiency arises from the combined, net effect of processes that are each very difficult to measure, such as predator prey mass ratio and trophic transfer efficiency. In this talk I will first briefly review the history of size spectra, and place Trevor Platt’s work into context. I will then use three examples of recent work to illustrate some diverse uses - but importantly also key limitations - of these size-based approaches. First, I will describe a recent global-scale compilation of data to examine the remarkable linearity of normalized size spectra, and how human depredation of the upper trophic levels has perturbed this. Second, I will describe how a global meta-analysis of size spectra can been used to quantify the trophic amplification of biomass declines, whereby a small, climate-induced decline in biomass at the base of the food web magnifies into much greater declines in the supportable biomass of fish. The third example also relates to climatic processes but at smaller scales; using size spectra as indicators of resilience of pelagic ecosystems to extreme storm events. 1Plymouth Marine Laboratory, UK 2023/08/11 (09:00-09:30)
Annual variations in the inherent optical properties along the coastal waters off Cochin 1Anju R, 2Nandini Menon N, 1Sara Xavier, 1,2Minu P, 1Pranav P, 3Anas Abdulaziz, 4Shubha Sathyendranath, 1Grinson George Poster Session 1 Water molecules and the optically active substances present in the water column absorb or scatter under water solar radiation. Thus, a thorough understanding of light interactions with the optically active substances and its propagation in water requires radiative transfer studies in aquatic ecosystems. A monthly sampling was conducted along the coastal waters off Cochin, in the south eastern Arabian sea, from November 2021 to December 2022 in order to evaluate the spatial and temporal dynamics of the inherent optical properties (IOP) of optically active substances. Water samples were collected from three stations with 5m, 10m and 20m bathymetry respectively for measuring the bio-optical variables. Ecology of the study area is complex as it experiences a tropical monsoonal climate, wind-induced upwelling and seasonal changes in hydrographic conditions. The ternary plots of IOPs showed that detritus was the principal light absorber in the coastal waters off Cochin. Highest chlorophyll-a (Chl a) concentration was recorded in the month of July. The current study aims at utilising the insitu data for IOP for calibration and validation of data retrieved from satellite remote sensors. High detrital load can impair the accuracy of the chl a remote sensing retrieval algorithm. The study also focuses on proving the efficacy of the existing regional satellite algorithms. The findings in turn will substantially contribute to refining regional optimized algorithms for retrieval of optically active substances in the study area from remote sensing. Key words: Optically active substances, Arabian sea, inherent optical properties, detritus matter, satellite remote sensing. 1ICAR-Central Marine Fisheries Research Institute, India; 2Nansen Environmental Research Centre (India), Cochin; 3CSIR-National Institute of Oceanography, Regional centre, Cochin, India; 4Plymouth Marine Laboratory, Plymouth, Devon, UK 2023/08/09 (17:30-19:00)
Chemically mediated algae-Vibrio interactions 1Ann Mary V B, 2Joe Hedges, 1,3Perle Daibes, 2Bob Brewin, 1Shubha Sathyendranath, 1Mahasweta Saha Poster Session 1 Members of Genus Vibrio are naturally abundant heterotrophic bacterial species in the marine environment. They are found to associate with phytoplankton and other substrates like macrophytes and zooplankton for their persistence and survival in the ocean. Several members of Vibrio are known to be pathogens causing vibriosis. Studies have recognized correlation between increasing abundance of Vibrios with phytoplankton association. However, information on the chemical mechanisms and cues driving this association is very limited. In this foundation work, we evaluated the settlement of three pathogenic vibrios (V.injenensis,V.vulnificus, V.parahaemolyticus) and three non-pathogenic Vibrio species on phytoplankton crude cell extracts.Phytoplankton species tested were Skeletonema marinoi,Thalassiosira pseudonana ,Chaetoceros calcitrans,Phaeodactylum tricornutum,Prorocentrum micans and Coscinodiscus radiatus.One-way ANOVA analysis revealed that all phytoplankton extracts were effective in inhibiting settlement of all tested species of Vibrios. However, V.rumoiensis was attracted to all phytoplankton extracts except C.calcitrans extract. This observation implies the presence of species-specific attractive or deterrent compounds that may exist driving this association. Additionally, polar and non-polar fractions from crude extracts of phytoplankton were also analyzed for anti-settlement effect. Our results reveal the presence of anti-Vibrio compounds in polar fractions of S.marinoi, C.calcitrans extracts, whereas T.pseudonana was found to have active compounds in non-polar fraction. As further study we will explore the chemical compounds driving this association and how climate change induced stressors might change this interaction. Results will enable us to understand dynamics of phytoplankton-pathogenic marine bacteria interaction, particularly Vibrios that represent an emerging disease threat in Europe and other higher latitudes, due to climate change. 1Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, United Kingdom; 2University of Exeter, Penryn,Cornwall, UK; 3University of Plymouth, Plymouth, UK 2023/08/09 (17:30-19:00)
Environmental monitoring of shifts in the plankton community composition in the North Sea for an offshore CCS project 1Anna Rufas Blanco, 1Heather Bouman Poster Session 2 Offshore carbon capture and storage (CCS) projects are planned in the North Sea as part of the UK national response to decarbonise our economy and achieve net zero. The North Sea is a testing ground for deploying offshore subseafloor carbon dioxide (CO2) storage technologies. That is due to the abundance of geologically stable depleted oil and gas reservoirs, where the CO2 emitted by carbon-intensive industries can be safely injected. However, minor leakages of CO2 at the seafloor are expected due to small fractures, and their local impacts on the marine ecosystem need to be assessed. The carbonate system will be the first to be impacted by the bubbling of CO2, with local changes in pH that could affect life in the sea. In particular, changes in pH could affect biological processes such as calcification by planktonic organisms, primary production, secondary production and shifts to harmful microbial species that, in normal conditions, are rare. To date, there exists no baseline assessment of the marine community composition in the North Sea that could help us differentiate between the build-up of CO2 in near-bottom waters due to CO2 leakage and the natural variability of the local ecosystem (e.g., cumulative remineralisation of sinking particulate organic carbon). Here, we will present a baseline data assessment of the planktonic community composition in a region of the North Sea where a CCS project has been planned, providing a long-term picture of the regional spatiotemporal variability against which anomalies could be identified. 1University of Oxford, UK 2023/08/10 (17:00-18:30)
Preliminary results of oceanographic data from the G-NEO1 time series in the Nuevo Gulf, Argentina 1,2Antonella De Cian, 1,2Augusto Crespi-Abril, 1,2Rodrigo Hernández Moresino, 1Lucia Epherra, 1,2Juan Pablo Pisoni, 1,2Elena Susana Barbieri Poster Session 2 Since coastal marine environments present a great diversity of natural processes, continuous monitoring over time is required to understand the balance of factors observed in it. The aim of this work is to analyze the seasonal variability of oceanographic data in a coastal area of the Golfo Nuevo, Argentina. Surface monthly samples were analyzed from July 2021 to June 2022 at the Luis Piedrabuena pier (750 m from the coastline). The samples belong to the time series "Golfo Nuevo Estación Oceanográfica 1" (G-NEO1), supported by NANO-DOAP Project. In G-NEO1 temperature has been continuously monitored since 2010, and discrete oceanographic parameters since 2018 such as salinity, nutrient concentration, chlorophyll-a, the composition of the planktonic community (phytoplankton and zooplankton) and atmospheric conditions (winds and relative humidity reported by the Meteorological Information Center, and atmospheric dust measured in situ). The station is in a temperate sea, so it presents high temperature variations during the year (between 9.7 to 20.5°C). During periods where the water column is stratified and the concentration of nutrients is low, the phytoplankton community is dominated by nanophytoplankton (nanoflagellates in October and ciliates in January/February). In summer, high concentrations of dinoflagellates and ciliates were observed, and in autumn a bloom of the genus Chaetoceros. Maintaining a time series requires a long-term investment in trained personnel, institutions, and infrastructure that provide repeatable oceanographic measurements. The time series of in situ observations allows to know the variability of the ecosystem, to detect extraordinary events and identify anthropogenic effects. 1Laboratorio de Oceanografía Biológica (LOBio), Centro para el Estudio de Sistemas Marinos (CESIMAR), Centro Nacional Patagónico - Consejo Nacional de Investigaciones Científicas y Técnicas (CCT- CENPAT CONICET), Puerto Madryn, Argentina; 2Facultad de Ciencias Naturales y Ciencias de la Salud, Universidad Nacional de La Patagonia San Juan Bosco (UNPSJB). Puerto Madryn, Argentina 2023/08/10 (17:00-18:30)
Advantages of Monitoring Harmful Algal Blooms with Unmanned Aerial Vehicle for Oman Coastal Waters 1,2Arife Tugsan Isiacik Colak Poster Session 1 A water quality monitoring program evaluates the physical, chemical and biological characteristics of aquatic systems in relation to human health concerns, ecological conditions, and designated uses. Water quality is determined by the presence of contaminants and the characteristics of the water. They can be categorized as biological (bacterial, algae, HAB), physical (turbidity, temperature, suspended solid) and chemical (ph). As a result of these measurements, changes in water quality can be monitored. A major advantage of remote sensing observation for water quality monitoring is that it provides spatial and temporal information about the characteristics of surface waters. To monitor and identify causes of Chl-a increasing as a water quality indicator and create a strategy for the marine pollution sources of Oman Coast, to generate an advanced map of pollution sources and indicate potential risk areas for HAB for coasts of Oman, searching the abundance and frequency and distribution of algal blooms and to develop a uniform and systematic approach for identifying and discriminating type of Harmful Algal bloom types across Oman Coasts and regarding their spectral signature, to set a spectral library for HABs types and create HABs species archiving for Oman, to understand the factors that alter the timing of bloom events and determine the temporal frequency of HAB; advanced monitoring of Harmful Algal Blooms for Oman coastal areas by Unmanned Aerial Vehicles – Drone systems with hyperspectral sensors is very essential. This study explains the advantages of UAV- Drones for water quality monitoring and analysis for Oman's Coastal Waters. 1International Maritime College Oman; 2National University of Science and Technology, Oman 2023/08/09 (17:30-19:00)
Bio-optical complexity and radiant heating rates in the coastal waters of eastern Arabian Sea 1Arjun Adhikari, 1Partha PatiL, 1Harilal Menon Poster Session 1 The study aimed to elucidate the effect of bio-optical complexity on radiant heating rates in the coastal waters of the eastern Arabian Sea. The in situ measurements used in this study covered a large spatial domain between 9°35ʹN and 15°43ʹN and east of 72°58ʹE and comprised different bio-optical measurements and in-water light field along the pre-determined nine transects in the vicinity of riverine discharge sites influenced by Indian Summer Monsoon caused precipitation. In addition to the spatial survey, time series measurements were also performed at 15°27ʹN and 73°42ʹE at a depth of 20 m. By analyzing the distinctness in surface remote sensing reflectance, data were clustered in four water types, representing different conditions of bio-optical complexity. The most and least turbid water types had the highest and lowest concentrations of bio-optical constituents, respectively. The computations revealed that the radiant heating rate within the euphotic depth of most turbid water types was similar to those of least turbid; however, the euphotic depth of most turbid water types was manifold lower than least turbid. The study outcomes were compared with the in-situ spectral absorption and backscattering coefficients. It revealed that higher absorption and backscattering of the visible light spectrum in turbid waters restricts the underwater transmission of light leading to radiant heating rates of 0.21±0.12°C hr-1. We further discuss the effects of absorption and backscattering by bio-optical constituents and the importance of water types in the region concerning the bio-optical feedback crucial in coastal heat budget studies. 1Goa University, India 2023/08/09 (17:30-19:00)
Coupling between hydrography and bio-optical constituents in a shallow optically complex region using ten years of in-situ data 1Arjun Adhikari, 1Harilal B. Menon Oral Session 1: Physical and biological interactions This study aims to understand the coupling between bio-optical variability and seasonally changing hydrography using ten years of in-situ data from a shallow optically complex region located on the west coast of India. The long-term measurements of bio-optical constituents covered wide-ranging hydrography conditions and three seasons experienced in the region, i.e., Indian Summer Monsoon (ISM), post-ISM, and pre-ISM. From the spatial variability of bio-optical parameters and state of hydrography, four groups were classified, (i) collocated strongest stratification and maximum total suspended matter (TSM) concentrations, (ii) collocated maximum chlorophyll-a (Chl-a) and moderate stratification, (iii) weakly stratified riverine stations, and (iv) estuarine/coastal shelf sampling stations. There was less variability at stations of strong stratification and bio-optical parameters in the ISM and post-ISM seasons. In the pre-ISM season, the location of maximum stratification shifted upstream, and maximum Chl-a was always located immediately downstream of stations with maximum TSM. Surprisingly, colored dissolved organic matter (CDOM) values were negligible in the ISM season and increased manifold in other seasons. The source of CDOM (either land-derived or in situ generated) from the spectral slope revealed the significance of land-derived CDOM in the post-ISM season. Comparing the spectral diffuse attenuation coefficient of downwelling irradiance with total absorption and backscattering revealed that maximum TSM and estuarine/shelf sampling locations were scattering-dominated. In contrast, the group with maximum Chl-a was absorption dominated. In the study region, the dominance of either absorption or scattering depended heavily on the contribution of Chl-a to the absorption budget and state of stratification. 1Goa University 2023/08/09 (12:15-12:30)
Estimation of mangrove Extent in Kala Oya Estuary, Sri Lanka using Landsat 8 and Sentinel-1A imagery in Google Earth Engine cloud computing platform 1Ayantha Abeygunawardana, 2Sevvandi Jayakody, 3Eric Wikramanayake, 4Chathurangi Wickramarathne Poster Session 2 Mangroves are fragile, sensitive and dynamic ecosystem which severely affect the alternation of habitat. That has driven the attention for monitoring and conservation. The effective conservation may depend on continuous monitoring the changes, extent, structure in this unique assemblage. Low and medium resolution freely available optical images are not properly explained the structural characters which vary with dynamic ecosystem. The study aims to estimate the extent of mangroves as an integrated approach of optical data( Landsat 8 ) and Radar (Sentinel-1 C-band Synthetic Aperture Radar (SAR)by considering structural characters in 2017, 2019 and 2021. The Landsat Surface Reflectance Tier1 extracted in the respective time period and Extracted images were further enhanced using cloud mask. The final Color composite was compiled using median reducer based on study area, spectral indices (Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), SRTM data for narrow down to low elevations, which occurs mangroves in the coastal area. The training data set for mangroves and non mangroves was derived based on the ground observations and prepared model was evaluated through the random forest classifier. The obtained results from the optical image were refine the output by evaluate random forest classifier for SAR Data. The Mangrove extent of Kala oya estuary gradually changed 436.85ha,478.56ha ,477.56ha in 2017,2019,2021 respectively, The resultant mangrove forest map of Kalaoya Estuary at 30 m spatial resolution has an overall/users/producer’s accuracy greater than 90%, validated with ground reference data. The study has demonstrated the potential method for correctly classified the mixed pixels (Water and Vegetation) and integrated approach for identify the changes of mangrove vegetation using the freely available satellite images using GEE platfo 1Department of Animal Science, Faculty of Animal Science and Export Agriculture, Uva WellassaUniversity, Badulla 9000, Sri Lanka; 2Department of Aquaculture and Fisheries, Wayamba University of Sri Lanka, Makandura, Gonawila, 60170, Sri Lanka; 3WWF Hong Kong, Kwai Chung,Hong Kong; 4International Water Management Institute (IWMI), Sri Lanka 2023/08/10 (17:00-18:30)
Expanding the use of Copernicus marine satellite data: EUMETSAT’s user support and training activities 1Benjamin Loveday, 1Hayley Evers-King, 1Sally Wannop, 1Christine Träger-Chatterjee, 2Vittorio Brando, 3Ana Ruescas, 4Aida Alvera-Azcárate Poster Session 1 Following the successes of the first phase of the European Commission Copernicus programme, EUMETSAT is continuing and expanding its offer of data access services, marine data products, as well as marine training activities and user support services, under phase two. EUMETSAT operates the Sentinel-3, Sentinel-6 and Jason-3 satellites, and provides level-1 and level-2 marine data products for ocean colour, sea surface temperature, and altimetry science and applications. User support services include data access, customisation, and visualisation platforms, web-based technical information about products, as well as a help-desk available to answer a full range of user queries on the products and their use. Interactive training activities are designed to accommodate a diverse range of audiences, both research and operational, putting trainee needs and interests at the centre of learning objectives. A focus on co-development of resources and participant-led learning interventions allows participants to tailor their own experiences towards development of the skills and knowledge that will help them in their own applications and work tasks. Building on four years of successful general courses, EUMETSAT now seeks to develop further specialised training and advanced courses for the marine community. This presentation will showcase existing services and resources, and provide information on planned training events for 2023 and beyond. It will expand on our training approaches and provide further information on opportunities for collaboration with the wider marine community, during the UN ocean decade. 1European Organisation for the Exploitation of Meteorological Satellites, Germany; 2The Institute of Marine Sciences of the National Research Council of Italy (CNR-ISMAR), Italy; 3Brockman Consult GmbH and University of Valencia, Spain; 4University of Liege GHER, Belgium 2023/08/09 (17:30-19:00)
An interactive web-based frontend for visualising and conducting analysis on time series of ocean observations 1Benjamin O'Driscoll, 1Darren Snee, 1Peter Walker, 1Ben Calton, 1Daniel Clewley Poster Session 2 The use of Earth Observation, Modelling and Artificial Intelligence (AI) in marine science is producing ever increasing volumes of ocean data. Providing a way to interact with and visualise these datasets is key to them being fully utilised. PML has developed a web-based portal to allow for easy temporal control and analysis of geospatial datasets which has been utilised in several projects to make outputs available to external users. One such example is the ESA Ocean Colour Climate Change Initiative Project (OC-CCI) which provides a global record of chlorophyll concentration (along with other variables) from satellite data from 1997 to the present. Recently the portal has undergone several improvements to make use of newer technologies and improve performance when dealing with larger volumes of data. Increasingly, the portal is being used as a tool within research, providing a means to interrogate preliminary outputs. This discussion will provide an update on recent developments to the portal that better facilitate the visualisation of time series datasets, show case studies of how it is being used within research and solicit feedback on priorities for future development. PML looks to collaborate alongside others in this community to visualise and analyse more data in this way and to enhance the portal with features that both researchers and end users will need in the future. 1Plymouth Marine Laboratory, UK 2023/08/10 (17:00-18:30)
Lab on a mini-Secchi disk 1Bob Brewin, 1Tom Brewin, 2Philip Bresnahan Oral Session 5: Water Quality and human health In collaboration with Trevor Platt and colleagues, a simple hand-held device (mini-Secchi disk) was developed in 2013, designed to measure the Secchi depth and water colour (Forel Ule colour) of lake, estuarine and nearshore turbid waters. The mini-Secchi disk is inexpensive to manufacture (using a 3D printer and basic workshop tools), lightweight, easy to use, and has proven useful for citizen science projects monitoring water quality. Here, we extend the device by integrating a small environmental sensor package (Arduino-based) into the Secchi disk. The package measures GPS, spectral light, temperature, and pressure. It is charged and transfers data wirelessly, is encased in epoxy resin, and can be used to derive vertical profiles of spectral light attenuation and temperature. We present a series of deployments of the device, compare its performance with commercially available instruments, and demonstrate its use a tool for evaluation of remotely sensed data. Based on open-source technology, it is well suited for low-cost monitoring of water quality. 1University of Exeter, UK; 2UniversityofNorthCarolinaWilmington, Wilmington, USA 2023/08/10 (14:30-14:45)
MOSS - A novel method to study dominating timescales of variability in global satellite Chl and SST fields 1Bror Jönsson, 2Joseph Salisbury, 1Shubha Sathyendranath, 1Elisabeth Atwood, 3Amala Mahadevan Poster Session 1 Marine ecosystems are not only defined by the general abundance of primary producers, but also their variability. In many regions of the ocean, biological production is punctuated by hotspots and blooms that exhibit a high spatial and temporal variability in the phytoplankton biomass. Satellite-derived proxies for biomass such as Chlorophyll (Chl) provide unprecedented coverage in time and space but are sparse with gaps from clouds etc. about 80% of the time. We have developed a new method to estimate dominating timescales of variability based on calculating the standard deviation of the time series data over moving windows of a set time interval and repeating for different time-interval windows. Our results show that the method can assess dominating timescales (τ_d) in time series where data coverage is sparse. We find that τ_d values for SST generally varies on longer timescales than Chl. There is a threefold variability in τ_d for SST and Chl, even within regions that are traditionally considered to be biogeographically homogeneous. Our findings, while novel by themselves, have the potential to help explain patterns in observed global phytoplankton biodiversity; for instance, small organisms might have a competitive advantage in regions with short dominant timescales. Another potential use would be to constrain estimates of carbon export from the surface ocean for regions where it has been suggested that the timescales of biomass change may play an important role. We believe that the MOSS method can provide a framework for a concerted approach to connect variability in phytoplankton biomass and biological production with export production and export efficiency. 1Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, United Kingdom; 2University of New Hampshire, US; 3Woods Hole Oceanographic Institution, US 2023/08/09 (17:30-19:00)
Taking a dive into “El Veril”: A coastal time series monitoring by citizen science divers in Argentina 1Carla F Berghoff, 1,2Lucía Epherra, 3Guadalupe A Ramis, 1Ricardo I Silva, 1Jorge Fernández Acuña, 1Ana Baldoni, 1Reinaldo A Maenza, 1M Constanza Hozbor, 1Macarena Albornoz, 1Bruno V Menna, 1,2M Guadalupe Cascallares, 2,3Diego Moreira, 4citizen science divers Poster Session 2 Oceanic uptake of anthropogenic carbon dioxide plays a key role in moderating climate change, however this capture affects the chemistry of the carbonate system (CS), decreasing ocean pH, a phenomenon called ocean acidification (OA). OA generates substantial impacts on the marine ecosystem and the services provided by the ocean. The CS dynamics in coastal regions is extremely variable, hence efforts to better understand its sensitivity to OA are being carried out worldwide. One of the contributions towards the evaluation of OA in Argentina is the monitoring of the coastal site “El Veril” (38°10'S 57°25'W), carried out by researchers from INIDEP and scuba divers from CASE in a citizen science context. CASE divers frequently visit “El Veril” due to the diversity of marine organisms, where they collect samples to determine different physicochemical and biological variables (CS, oxygen, nutrients, salinity, chlorophyll-a and microbial communities), and document the temperature and sea conditions. This information is then analyzed in an OA context. Since 2018, more than 40 divers have carried out 26 samplings. We will present the results of this collaboration, which already cover a complete annual cycle, and how this contributes with valuable information at local (National Citizen Science Program) and international level (NANO-DOAP Project). Additionally, we will present the outreach events held by INIDEP-CASE to improve public awareness about how human activities threaten the health of the ocean. This initiative, which provides knowledge on the CS, has an amplifying effect towards society, by improving citizen education on the challenges the ocean faces. 1Programa Dinámica del Plancton Marino y Cambio Climático, Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina 2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina 3Universidad Nacional de Buenos Aires (UBA), Buenos Aires, Argentina 4Centro de Actividades Submarinas Escualo (CASE), Mar del Plata, Argentina. 2023/08/10 (17:00-18:30)
Distribution of HAB species, dinoflagellate cysts and antonymous nature of freshwater phytoplankton in two tropical estuaries along the West coast of India 1Chandrashekher Rivonker, 1Samiksha Prabhudessai, 1Vishal C R Poster Session 1 The present studies carried out elucidate the seasonal distribution of HAB species, cyst and their ecological interactions in two tropical estuaries, namely Chapora and Sal along the west coast of India. A total of 17 species of diatoms belonging to nine genera and 13 species of dinoflagellates belonging to eight genera were recorded (monsoon and non-monsoon season). Among 13 species of dinoflagellates, 06 species are known as potentially toxic namely Alexandrium minutum, A. tamarense, A. pseudogonyaulax, Cochlodinium polykrikoides, Prorocentrum micans and Gonyaulax spinifera. Dinoflagellate cysts (16 species) belonging to the order, Gymnodiniales, Gonyaulacales, and Peridiniales were recorded in the surface sediments. Redundancy analysis revealed that the salinity and phosphate concentration influence the distribution of HAB-forming species in both the estuaries. On the other hand, cysts of heterotrophic dinoflagellates dominated in both the estuaries and revealed that the distribution of the cysts were mainly influenced by salinity and grain size. Nitrate limitation is noted to be a triggering factor for cyst formation as revealed from inverse relationship, suggesting high nitrate input in these estuaries might lead to excystment of Gonyaulax spinifera. The MDS plots revealed salinity as one of the crucial parameters in the distribution of freshwater phytoplankton. Among these estuaries, Sal was represented with a high diversity of toxic species, associated with high phosphate and nitrate content in the water column. Further, the results indicate that the bloom of A. minutum suppressed the growth of other species of diatoms and dinoflagellates, suggesting its possible allelopathic effect. 1Goa University, Goa, India 2023/08/09 (17:30-19:00)
Water quality and health risk assessments of illegal gold mining-impacted estuaries in Ghana 1Charles Abimbola Fasseyi, 2Michael Miyittah Oral Session 5: Water Quality and human health This study evaluated the water quality, pollution, and health risks associated with illegal gold mining activities in two estuaries (Pra and Ankobra) in the Southwestern region of Ghana. The Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) used for the evaluation indicated that both estuaries were in the marginal water quality category. Nemerow's Pollution Index (NPI) evaluation showed that turbidity (from siltation), PO4, Pb, Cu, and Fe contributed to the pollution of the two estuaries. The health risks index of Target Hazard Quotient (THQ) and Total Hazard Index (HI) evaluated on shellfish (Macrobrachium) from the estuaries were above USEPA recommended threshold; therefore, there is a likelihood of human health risks impacts on the coastal dwellers surrounding the estuaries. Overall, the study buttresses the need to take urgent strategic actions to control the direct impacts of pollution on the estuarine systems and the surrounding coastal communities. 1Department of Fisheries and Aquatic Sciences, Centre for Coastal Management, University of Cape Coast, Ghana; 2University of Cape Coast, Ghana 2023/08/10 (14:45-15:00)
Estimation of particulate inorganic carbon concentration in the surface layer of the global ocean: a two decadal satellite analysis 1Christina Eunjin Kong, 1Shubha Sathyendranath, 2Catherine Mitchell, 3Robert J. W. Brewin, 1Thomas Jackson, 1Bror Jönsson, 1Gemma Kulk, 1Andrei Chuprin Poster Session 1 Particulate inorganic carbon (PIC) plays a vital role in the ocean carbon cycle. Accurate estimates of PIC concentration from satellite observations can allow us to examine long-term changes in the PIC pool on large scales. In this study, we examine the performance of a previously-reported algorithm and of a newly-developed random-forest approach to estimate PIC concentration in the surface waters of the global ocean, using a multi-sensor merged satellite product — that of the Ocean Colour Climate Change Initiative. A large set of in situ PIC data was used to develop the random-forest-based PIC algorithm and to test the performances of the two algorithms studied here. Our results show that the random forest approach can retrieve the PIC concentration relatively well on large scales. Using this approach, we explore two decades of spatiotemporal dynamics of satellite-derived PIC concentration in the surface layer of the global ocean. We also discuss gaps, challenges, and future needs in support of establishing a long-term, high-quality record of PIC data from space. 1Plymouth Marine Laboratory, Plymouth, Devon, UK; 2 Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, USA; 3Centre for Geography and Environmental Science, University of Exeter, Penryn, Cornwall, UK 2023/08/09 (17:30-19:00)
Characterising and monitoring phytoplankton properties from satellite data 1Conor McGlinchey, 2Jesus Torres Palenzuela, 2Luis Gonzalez Vilas, 3Mortimer Werther, 4Adriana Constantinescu, 4Adrian Stanica, 5Shenglei Wang,5Junsheng Li, 1Andrew Tyler, 1Evangelos Spyrakos Poster Session 1 Harmful Algal Blooms (HABs) pose a great threat to human and animal health, their occurrence also has a significant impact on a variety of socio-economic and environmental factors. HAB events are now a global problem and is expected that the occurrence of HABs is likely to grow significantly with the increase in human population coupled with climate change. This study will draw on satellite sensors which differ in spatial, spectral, and temporal resolution: Sentinel-2, Sentinel-3. The objectives of this study are to develop and validate HAB detection algorithms for near-shore and coastal waters, with better generalisation capability and lower computational overload that could improve the identification of the optical characteristics directly associated with phytoplankton properties. The research will be focused on four optically diverse regions of interest; The Danube Delta and Black Sea Coastline (Romania), Galician Coast (NW Spain), Shandong Peninsula Coast (China) and the Northern-South China Sea (China). Here, we will present results from the Galician coast and other European waters. We used in-situ data such as hyperspectral Remote Sensing Reflectance, Chlorophyll-a concentration, phytoplankton abundance and taxonomy, along with fractionated chlorophyll-a and particle absorption properties to develop and test the algorithms. We focus on the detection of Alexandrium minutum from Sentinel-2 MSI and Sentinel-3 OLCI data. We tested different atmospheric correction models against in-situ hyperspectral data and evaluated their performance over coastal waters. We will present results on the optical characteristics of A. minutum and the potential of MSI and OLCI for their remote detection. 1University of Stirling, Scotland; 2University of Vigo, Spain; 3Swiss Federal Institute of Aquatic Science and Technology, Switzerland; 4GeoEcoMar, Romania; 5Aerospace Information Research Institute Chinese Academy of Sciences, China 2023/08/09 (17:30-19:00)
Machine learning for Ocean Colour Satellite Sensor Bias Correction 1David Moffat, 2Thomas Jackson, 2Leander Fernandes Poster Session 1 Remote sensing of ocean colour (OC) remains an evolving field of science with new sensor capabilities, in-situ data sets and algorithmic approaches being developed continuously. A powerful recent addition to many scientific fields is machine learning, enabled by the massive volumes of data available, with remote sensing of ocean colour being very suitable for Machine Learning (ML) application. Here we demonstrate the potential for a trained ML algorithm to correct data for differences between ocean colour sensors, a process known as inter-sensor bias correction. This method aims to produce a single unified ocean colour sensor and produce images that can be compared across multiple OC sensors without the individual bias and offsets present within each sensor. A neural network approach has been used to improve existing bias correction methods, and provisional results demonstrate an improvement on bias correction. This correction is essential in the generation of long climate datasets from multiple sensors to ensure that artifacts are not introduced to the timeseries when the set of sensors contributing to the record changes. We discuss the requirements on training data, general applicability/extensibility of the method, implications for the ML approach for different geographic regions, and compare the ML output to existing statistical approaches used within the OC-CCI project. 1Plymouth Marine Laboratory, UK; 2University of Bristol, UK 2023/08/09 (17:30-19:00)
The dynamic observation of organic matter in the Pearl River Estuary in China 1Dong Liu, 1Yan Bai, 1Xianqiang He, 1Delu Pan, 1Difeng Wang Poster Session 1 The distributions of estuarine colored dissolved organic matter (CDOM) are the combined results of physical-biogeochemical processes. Remote sensing is needed to monitor highly dynamically estuarine CDOM. Using in-situ data from four seasonal cruises, an algorithm is developed to estimate CDOM absorption coefficient at 400 nm (a CDOM (400)) in the Pearl River Estuary (PRE). The algorithm uses band ratios of R rs (667)/R rs (443) and R rs (748)/R rs (412). By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite (MODIS/Aqua) data from 2002 to 2014, seasonal climatology a CDOM (400) in the PRE is calculated. CDOM distributions are majorly influenced by water discharge from the Pearl River and underwater topography. Along the section vertical to a water depth gradient, the seasonal a CDOM (400) exponentially decreased (y=ae bx , b<0), but with great differences among seasons. Riverine fresh water is the primary source of CDOM in the PRE. Fulvic acid fraction decreases with increasing salinity. Using developed algorithms, conservative CDOM mixing equation, and river discharge, effective riverine end-member concentration and flux of dissolved organic carbon (DOC) in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data. Both effective riverine end- member DOC concentration and flux are positively related to the river discharge, significantly in summer with R 2 of 0.698 for concentration and 0.9657 for flux. 1Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China 2023/08/09 (17:30-19:00)
Probabilistic models of Harmful Algae Blooms: Application to the Norwegian Coast 1Edson Filisbino Freire da Silva, 1Julien Brajard, 1Francois Counillon Poster Session 1 The monitoring of harmful algae blooms (HAB) is sparse and discontinuous as the process is time-demanding and expensive. Probabilistic forecasts of HABs can help identify regions and periods for which the risk of high intoxication increases and can help improve the monitoring program. We build a HAB probabilistic model for the toxic Alexandrium tamarense and Dinophysis acuta by using support vector machines. We use 15 years of in situ weekly HAB observation from the Norwegian coast and relate the probability of HAB events (cells/L>200) to environmental factors obtained by remote sensing and modeling, such as sea surface temperature (SST), photosynthetically active radiation (PAR), mixed layer depth (MLD), and sea surface salinity (SSS). The dataset is split into training (2006 - 2013) and testing (2014 – 2020) periods. By comparing the estimated probabilities to the frequency of HABs, the models show a correlation of 0.9 and 0.94 and RMSE of 1.3 and 1.1% for A. tamarense and D. acuta. The A. tamarense HABs are mostly related to MLD below 50 m and SSS above 32 PSU, while The D. acuta HABs are related to SST at 15°C and PAR from 1.4 to 30 E/m²d. The models can predict periods when HABs of D. acuta and A. tamarense have no risk of occurring and seasonal windows when HABs are likely to occur. Probabilistic maps of both species are provided, with D. acuta HAB’s having the highest probabilities in the west and south and A. tamarense having the highest probabilities in northern Norway. 1Nansen Environmental and Remote Sensing Center, Norway 2023/08/09 (17:30-19:00)
Phytoplankton Community Determination in the Baltic Sea based on HPLC Pigments Analysis of six oceanographic campaigns (2004-2008) 1Elisabetta Canuti, 2Antonella Penna Poster Session 2 Identification and estimation of phytoplankton community composition and abundance based on the chemotaxonomic phytoplankton pigments concentration determined by High-Performance Liquid Chromatography (HPLC) technique is a consolidated approach in the ecological studies. The present study consider the of pigments compositions characterized by HPLC of surface natural samples collected between 2004 and 2008 during six oceanographic cruises on the Baltic Sea (BA) and representative of different seasonal conditions and bloom occurrence. Several data analysis techniques were applied to the data set, including hierarchical clustering, Principal Component Analysis and investigation on network community identification, in order to identify connection between phytoplankton pigment markers, phytoplankton community and physical-chemical influence occurrence during six campaigns on Baltic Sea. The preliminary results indicate the presence of four dominant phytoplankton communities: cyanobacteria, dinoflagellates, diatoms and cryptophytes. The distribution of the dominant community among the different cruises is characterized and compared with results obtained by more commonly applied technique, such as CHEMTAX and regional bio-optical algorithm for the estimation of Phytoplankton Functional Types (PFTs) and Phytoplankton Size Classes (PSCs) Composition. The community composition was then object of consideration in terms of seasonal variability and bloom occurrence in the Baltic Sea over the 5 year period time cover by the oceanographic campaigns. 1Joint Research Center, European Commission; 2Urbino University Carlo Bo, Italy 2023/08/10 (17:00-18:30)
Can we model cholera cases using chlorophyll–a? a mathematical modelling study 1Elizabeth Goult, 2Christina Eunjin Kong, 2Shubha Sathyendranath, 2Trevor Platt Poster Session 2 Vibrio cholerae, the causative agent of cholera, is a component of aquatic ecosystems where their survival is dependent on environmental conditions such as water temperature and salinity. The aquatic environment, as well as phytoplankton and zooplankton in the water, serve as reservoirs of V. cholerae. Their association with phytoplankton and zooplankton (for which phytoplankton is a source of food), has led to inclusion of the main phytoplankton pigment, chlorophyll-a, in empirical models designed to predict risk of cholera from environmental conditions. We developed a deterministic model of cholera transmission, coupled to a model of environmental V. cholerae. The model was then fit to time-series data from a South Indian coastal lake, Vembanad Lake on V. cholerae in water, and to reported cases of Acute Diarrheal Disease (ADD) from two sources: case counts from hospitals in three districts surrounding the lake, and outbreak reports from a surveillance programme. Of note, we observed different dynamics between the data sources. The model successfully reproduced seasonal patterns in V. cholerae concentration, reproducing the biannual peak in concentration observed in the lake, but failed to capture the dynamics observed in the number of ADD cases from either data source. Parameter fitting indicated that a high proportion of cases go unreported, which may explain the differing dynamics between the data. Our results show that chlorophyll-a can be used as a proxy for phyto- and zooplankton to model seasonal forcing in a V. cholerae population model; however, to improve prediction of cholera cases, better monitoring of cholera is needed. 1Max Planck Institute for Infection Biology, Germany; 2Plymouth Marine Laboratory, UK 2023/08/10 (17:00-18:30)
Eutrophication risk assessment for aquaculture developments in stratified, slow-flushing environments 1Erin King, 1Alan Hills, 1Rebecca Seal Poster Session 1 Coastal eutrophication can drive accelerated phytoplankton growth, harmful algal blooms, and oxygen depletion, with detrimental impacts upon marine ecosystems. Nitrogen is typically the limiting nutrient for phytoplankton growth in Scottish coastal waters. Atlantic salmon (Salmo salar) aquaculture may present a significant anthropogenic nitrogen source (principally Ammonia), particularly in slower-flushing sea-lochs potentially vulnerable to eutrophication. Consequently, environmental impact assessments of proposed aquaculture developments consider nutrient enhancement levels. However, assessments typically use parameterisations of sea-loch nutrient enhancement that do not account for stratification and spatial variability in flushing rates. Here we show that a widely used parameterisation of sea-loch nutrient enhancement (Equilibrium Concentration Enhancement; ECE) may not be conservative when assessing risk under stratified, slow-flushing conditions. We examine the eutrophication risk of a proposed semi-enclosed aquaculture development in a highly stratified, slow-flushing sea-loch (Loch Long). Comparisons are made between a calibrated 3-dimensional biogeochemical model (MIKE), a “conservative-tracer” nutrient dispersion model, and the ECE parameterisation. Our results indicate surface freshwater flux drives seaward nutrient transport in Loch Long. Reduced vertical mixing due to stratification leads to slow nutrient flushing, greater accumulation, and elevated phytoplankton growth. The ECE approach considers the entire sea-loch volume and therefore does not capture this spatial variability, nor the effects of stratification, consequently predicting lower enhancement concentrations. However, all approaches indicate the proposed discharges would comply with environmental quality standards in this case. Our results indicate that in complex stratified environments the ECE approach may not be conservative, and baroclinic numerical modelling should be considered in environmental risk assessment. 1Scottish Environment Protection Agency, Scotland 2023/08/09 (17:30-19:00)
Interannual variability of carbon and nutrient subduction in the Southern Ocean 1Essowe Panassa, 2Christoph Völker, 2Dieter Wolf-Gladrow, 2Judith Hauck Oral Session 4: Physiological ecology of marine phytoplankton Southern Ocean carbon and nutrient subduction/obduction rates in the period of 1958 to 2016 across the base of the winter mixed layer were assessed using an ocean biogeochemical model and were analysed with regard to the positive trend in the Southern Annular Mode (SAM) index. The time-averaged and spatially-integrated gross subduction rates of carbon and nutrients south of 30S were estimated to be 167.7 PgC yr-1 (dissoloved inorganic carbon, DIC), 113.9 Tmol N yr-1 (dissolved inorganic nitrogen, DIN), 159.8 TmolSi yr-1 (dissolved silicic acid) and 2.0 Gmol Fe yr-1 (dissolved Fe). This is balanced with gross obduction rates of -151.0 PgC yr-1, -135.5 Tmol N yr-1, -203.7 Tmol Si yr-1 and -2.3 Gmol Fe yr-1. The variations in SAM lead to large-scale anomalies in carbon and nutrient subduction/obduction rates that are zonally symmetric. We have also investigated the net carbon and nutrient subduction/obduction rates in the density classes of the strongest subduction/obduction. The carbon and nutrient subduction rates varied more on the interannual time scale before 1990 and follow a decadal trend since then. The net carbon and nitrate subduction rates in the highest subduction density class have increased by 3.5 TgC yr-1 (19%) for carbon and 2.1 Gmol yr-1 (25%) for nitrate over the past 69 years. In contrast, the net subduction rates of iron and silicic acid have decreased by 12.2 Kmol yr-1 (9%) and 0.8 Gmol yr-1 (18%), respectively. In the upwelling region, the net obduction rates of carbon and nutrients increased over time. This suggests that the positive SAM over the least decades has increased upper ocean circulation in the SO. These changes in the carbon and nutrient subduction rates might impact the carbon cycle and primary productivity in low latitudes. 1Department of Physics, Faculty of Science and Technology (FaST), University of Kara, Togo; 2Alfred Wegener Institute, Germany 2023/08/10 (11:45-12:00)
Assessing water quality and hydrodynamics in the central coast of Bangladesh: a Delft3D modelling approach 1Eurida Liyana, 1Kazi Mainul Islam Nirab, 1Md Shahadat Hossain, 1Subrata Sarker Oral Session 5: Water Quality and human health The central coast of Bangladesh hosts the most vibrant estuarine ecosystem in the country, providing vital breeding and nursing grounds for commercially valued fish species. Consistent monitoring of water quality is crucial for managing and conserving the feeding ecology of these species, which is currently absent. To address this gap, this study presents a first attempt to assess hydrodynamics and water quality of the central coast employing numerical simulation. Delft3D FM suite was used to implement a coupled hydrodynamic-water quality model for simulating dissolved oxygen (DO) in the central coast. In situ data for water level, temperature, salinity and DO were compared to simulated results and model performance was assessed using root mean square error (RMSE) values. Results indicated that the model could satisfactorily reproduce the observed water quality conditions of the region. Simulated DO showed seasonal and latitudinal variability, exhibiting an increasing trend from river to coast. The highest DO levels (~7.2 mg/l) were found to occur in the estuarine region during the pre-monsoon period (January-March) and DO was found to decline with the approaching of the monsoon, reaching the lowest levels (≤ 5.6 mg/l) in August. This seasonal pattern indicated that the influx of turbid water across the central coast during monsoon inhibits primary production reducing DO. However, DO remained well above hypoxic levels (> 4 mg/l) in all seasons, implying a healthy ecosystem for aquatic species. This research presents a methodology for regular monitoring of water quality in the central coast for adopting proper management strategies. 1Shahjalal University of Science and Technology, Bangladesh 2023/08/10 (14:15-14:30)
Status Of Marine Litter In Tanzania Along The Western Coast Of The Indian Ocean: A Case Study In Dar Es Salaam 1Frolence Jovinary Peter, 1,2Florence Jovinary, 1Marc Kochzius Poster Session 2 Marine litter accumulation poses a significant threat to marine biodiversity as a whole caused by industrial production and resulting waste. Growing cities in the world are facing also the same problems of waste littering in the streets, including the study site Dar es Salaam. This litter ends up in the ocean via rivers due to poor waste management plans and policy, contributing to marine litter accumulation. Therefore, this study focused on the quantification of marine litter and the influence of rivers on marine litter accumulation during the rainy and dry seasons. The study took place along the coast of Dar es Salaam at Mbezi rainbow and Salenda beach close to Mbezi and Msimbazi river during the rainy season (April) and dry season (July) from 2019 to 2020. Clustering and MDS, ANOSIM, and one way-ANOVA were used for data analysis. A higher density of marine litter was found in rainy seasons from both sites Mbezi and Salenda beach. Locations (Mbezi and Salender) showed no significant differences (F(1, 106) = 2.63, p = 0.11 and there was no significant difference among zones (F (1, 106) = 3.8581, P = 0.05 but seasons showed significant differences p = 0.016. And the most marine litter is produced locally in Tanzania by 70% compared to foreign countries yet the marine litter trend decreased in three years from 5.7 ± 0.45 litter/m2 to 2.2 ± 0.54 litter/m2 at a rate of 0.4 per year. The study suggests proper policy to minimize and reduce marine litter. 1Institute Of Marine Sciences, Buyu Zanzibar; 2Vrije Universiteit of Brussels, Belgium 2023/08/10 (17:00-18:30)
Contribution of altimetry to the Gulf of Guinea climate resilience due to last decade sea level anomalies scenarios 1Franck Ghomsi, 1Mathieu Rouault, 1Roshin P. Raj, 1Antonio Bonaduce, 1Issufo Halo, 1Anny Cazenave, 1Ola M. Johannessen Poster Session 2 The Gulf of Guinea (GoG), which stretches from Liberia to Gabon with reports of high vulnerability to coastal flooding caused by relative or climate-induced sea level rise, is an example of how coastal sea level changes remain poorly understood, in contrast to the global and regional average sea levels measured by satellite altimetry missions. These coastal areas with large human densities, low elevations, noticeable subsidence rates, and/or poor adaptation ability are most at risk. The relationship between equatorial Atlantic Ocean variability and the coastal region (1° coastal band off the coast) of the GoG is investigated at interannual time scales from 1993 to 2021 (29 years) from recent altimetric products in order to understand its mitigation to sea level rise in a region where there is no reliable (non-existent) tide gauges data. The study focuses on the (extreme) warm and cold events that occur in both the GoG and the Atlantic Ninos and links them to the well-known Benguela Ninos occurrences that occur off the coast of Angola and Namibia. The trade winds relaxing in the western/central basin caused equatorial and subsequent coastal waves, which are generally accepted to be the cause of both catastrophes. A correlation between signals observed along the GoG with significant events depicted along the Angola-Namibian coastlines as the extraordinary Equatorial Atlantic Warming in 2010, 2012, and 2021 with the 2019 events depicted as the warmest in the last 40 years, which has never been reported in this region, using both altimetric monthly Sea Level Anomalies (SLA) and Sea Surface Temperature (SST) Anomalies. Interannual SLA along the equatorial domain are systematically analyzed, and it is found that they advance the West African coastal ones by 1 month, supporting the idea that equatorial wave dynamics are responsible for their creation and the northward propagation observed on the SLA attributed mainly to the Kelvin coastal trapped waves. Because of sparse in situ measurements and societal stresses due to the undergoing rising sea level facts, improved coastal altimetry geophysical corrections will be of great benefit to address sub-seasonal variability. 1Nansen-Tutu Center, Department of Oceanography, University of Cape Town, South Africa 2023/08/10 (17:00-18:30)
Uncertainties in ocean colour remote sensing – How metrology can help 1Frederic Melin Oral Session 2: Marine Optics & Ocean Colour As any geophysical product, ocean color (OC) satellite data of remote sensing reflectance RRS and derived products need to be accompanied by uncertainty estimates to allow an informed use of these data by the user community and a proper integration in climate science. Even though there is growing emphasis on the provision of uncertainties for satellite data, this practice is in its infancy in the field of OC, which can be partly explained by the fact that this is particularly challenging. OC remote sensing is affected by a large and complex ensemble of error sources, including errors associated with the top-of-atmosphere signal and the numerous assumptions and approximations needed to solve the remote sensing problem and find a solution for RRS, all this coupled with the complexity of optical properties in natural waters. Relevant issues are summarized, including the sources of uncertainties and the state of the art on the various approaches currently proposed to produce uncertainty estimates for OC data. The use of uncertainty tree diagrams and of ensemble data is illustrated. Uncertainty estimates for OC data traditionally have been estimated by comparison with field data, a process termed validation; its central role and limitations are also discussed, and how validation statistics can be interpreted in terms of uncertainties is presented. Finally, recommendations are introduced, ultimately aiming at promoting a metrologically sound processing and treatment of OC remote sensing products. 1Joint Reseach Centre (JRC) - European Commission, Belgium 2023/08/09 (14:45-15:00)
Field Intercomparison of Radiometer Measurements for Ocean Colour Validation 1Gavin Tilstone, 1Tom Jordan, 1Giorgio Dall’Olmo, 1Martin Hieronymi, 1Kevin Ruddick, 1Matthew Beck, 1Martin Ligi, 1Maycira Costa, 1D’Alimonte, 11Vincenzo Vellucci, 11Dieter Vansteenwegen, 1Astrid Bracher, 1Joel Kuusk, 1Viktor Vabson, 1Ilmar Ansko, 1Riho Vendt, 1Giuseppe Zibordi, 1Craig Donlon, 1Tânia Casal, 1Dirk Aurin, 1Charles Kovach, 1Michael Ondrusek, 1Vittorio Brando, 1Christophe Lerebourg Poster Session 1 Field inter-comparisons of radiometers are important to ensure agreement between data products coming from different international laboratories who support the validating of ocean colour satellite missions. Two radiometric field intercomparisons were conducted at the Acqua Alta Oceanographic Tower (AAOT) in the northern Adriatic Sea, to assess differences in the accuracy of in- and above-water radiometer measurements used for the validation of ocean colour products. The first was undertaken from 9 to 19 July 2018 and the second from 11 to 21 July 2022. During the first inter-comparison, above-water Seabird HyperSAS and TriOS RAMSES systems and in-water TriOS RAMSES and Biospherical-C-OPS systems were compared against the AERONET-OC SeaPRiSM system. For the HyperSAS and RAMSES the differences in nLw were 4.7% and 4.9%, respectively, which mainly arose from differences in Ed cosine response, the Fresnel reflectance value and NIR correction used. During the second inter-comparison, HyperSAS and RAMSES above water systems, automated sun-tracker systems, in-water Seabird HyperPro II and a floating RAMSES system were compared. A Common hyper-community processor was used to process data to reduce any potential differences between institutesInstrument uncertainties due to cosine response, nonlinear response, temperature, stray light and polarization were accounted for and computed. For nLw, using SeaPRISM as an independent reference, pySAS was the most accurate with <5% difference across spectral bands. For HyperSAS, and RAMSES-A differences were also <5% at blue and blue-green bands but were greater at red bands. 1Plymouth Marine Laborartory, UK 2023/08/09 (17:30-19:00)
Uncertainty Estimates For Satellite-based Computations Of Marine Primary Production 1,2Gemma Kulk, 1,2Shubha Sathyendranath, 1James Dingle, 1Thomas Jackson Poster Session 1 In their latest report, the IPCC expressed low confidence in satellite-based estimates of trends in marine primary production, citing the insufficient length of the time series as well as the lack of independent validation methods. Independent validation of basin-scale primary production estimates is compromised since all available in situ data from photosynthesis-irradiance measurements and all remotely-sensed data on chlorophyll concentration and available light are used for the modelling of primary production. Independent, concurrent, in situ, daily, water-column primary production measurements are not sufficient in numbers or in geographic distribution, for a global validation. Moreover, indirect methods of validation, such as the comparison with bulk property estimates, are compromised by incompatibility of time scales and representation of different components of primary production. In this study, we address the uncertainty in satellite-based primary production estimates by assessing the errors inherent to the calculation, in which each element of the calculation is considered separately. This method closely follows the validation approach described in the Guide to the expression of Uncertainty in Measurement (GUM). We assess the error in each of the input quantities to the primary production model (biomass, photosynthetic parameters and light) and propagate the errors through the model to obtain the uncertainty in primary production. By doing this on a pixel-by-pixel basis, we can address the uncertainties in primary production at regional scales and pinpoint regions where more in situ and remote-sensing data are needed to improve the confidence in satellite-based estimates of trends in marine primary production. 1Earth Observation Science and Applications , Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK; 2National Centre for Earth Observation, Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK 2023/08/09 (17:30-19:00)
Using multi-spectral remote sensing for flood mapping: A case study in Lake Vembanad, India 1,2Gemma Kulk, 1,2Shubha Sathyendranath, 1,2Trevor Platt1, 3Grinson George, 3Anagha Anudevks, 4Nandini Menon, 5Anas Abdulaziz Poster Session 2 Water is an essential natural resource, but increasingly water also forms a threat to the human population. Global warming, shifts in precipitation patterns and extreme weather conditions lead to water stress, including natural disasters such as floods or droughts that can cause severe damage to the environment, property and human life. A less studied aspect of such events is the impact on human health through waterborne diseases and on wellbeing through mental health problems. Action to reduce the risk is urgently needed, with more frequent floods and droughts already leading to climate refugees. Earth Observation has the potential for developing cost-effective methods to monitor risks to human health from water stress, with free and open data available at the global scale. In this study, we present the application of remote sensing observations to map flooded areas, using the Vembanad-Kol-Wetland System in the southwest of India as a case study. In August 2018, this region experienced an extremely heavy monsoon season, which caused once-in-a-century floods that lead to nearly 500 deaths and the displacement of over a million people. We review the use of existing algorithms to map flooded areas in Lake Vembanad using the spectral reflectances of the green, red and near-infrared bands from the MSI sensor on board Sentinel-2 - during August 2018 and in consecutive years during heavy monsoon seasons. Although the MSI sensor has no cloud-penetrating capability, we show that multi-spectral visible remote sensing can be used to generate flood maps to complement commonly-used SAR-based techniques to enhance temporal coverage (from 10-20 to ~5 days). In addition, multi-spectral visible remote sensing may be used for analysis of water quality as well as risk mapping of environmental Vibrio cholerae incidence, providing additional important services during natural disasters. 1Plymouth Marine Laboratory, Plymouth, UK; 2National Centre for Earth Observation, Plymouth Marine Laboratory, Plymouth, UK; 3Central Marine Fisheries Research Institute, Kochi, India; 4Nansen Environmental Research Centre (India), Kochi, India; 5National Institute of Oceanography, Kochi, India 2023/08/10 (17:00-18:30)
Trevor’s contributions to science and capacity building: An Indian perspective 1Grinson George, 2Nandini Menon N Oral Inaugural Session: International collaboration and capacity building Over more than three decades, Prof. Platt made innumerable and indelible contributions to Indian science, in particular to satellite remote sensing of ocean colour and allied fields. Prof. Platt emphasized the significance of primary production as a fundamental process that underpins marine ecosystems, and trained generations of young scientists in the field. Prof. Platt held the NF-POGO Visiting Professorship at CSIR–NIO, at Kochi, India. As the Executive Director of POGO, as the founding chair of IOCCG, and as part of his leadership roles in many international initiatives such as GEO Blue Planet, and JGOFS, he led various capacity-building activities. Prof. Platt and colleagues established SAFARI to promote applications of Earth Observation for fisheries and related fields, and organised the first SAFARI Symposium in 2010, in Kochi organized by ICAR-CIFT, in collaboration with many organisations such as NERCI, ESSO-INCOIS, ISRO-SAC, ISRO-NRSC, and CSIR-NIO. Prof. Platt conducted various international training programmes, workshops, and winter schools. As the Jawaharlal Nehru Science Fellow at ICAR-CMFRI, he dedicated himself to promoting satellite-based methods in fisheries research. He motivated us to organise the second SAFARI symposium, encouraging us to take leadership roles. He was a pioneer who explored the potential of space applications to study the health of aquatic ecosystems and its implications for vulnerable coastal communities. His legacy is still growing as his ideas materialise as new projects. Prof. Platt was involved in developing novel citizen-science activities in India. A non-profit international organization – the Trevor Platt Science Foundation – has been established in India, to carry forward his legacy. 1ICAR- Central Marine Fisheries Research Institute, India; 2Nansen Environmental Research Centre (India) 2023/08/09 (10:20-10:35)
Metabarcoding application to Planktonic Time-Series analysis 1Hannah Lloyd-Hartley, 1Jane Delany, 1Ben Wigham, 1Evelyn Jensen Oral Session 4: Physiological ecology of marine phytoplankton Marine plankton has short lifecycles and rapid reproductive rates enabling the organisms to respond swiftly to natural and anthropogenic change, becoming effective indicators. However, currently, diversity is a component that is not considered as an OSPAR indicator, due to the restrictions of traditional analysis. Traditionally planktonic samples have routinely been formalin-fixed and subsequently analysed through the identification of taxa to the highest taxonomic group by taxonomists under a microscope. The significant restraints and challenges are a time-consuming method, high financial cost with high planktonic diversity and a high number of morphologically difficult or indistinguishable taxa. Metabarcoding of eDNA, individuals and communities has confidently been used to detect and identify species in many taxonomic groups. However, formalin fixation causes damage to DNA, creating DNA and protein methylene cross-links. Protocols were developed and tested to undo the cross-link and extract identifiable DNA from the formalin samples. Using the COI mitochondrial gene, species and community diversity are identified using libraries and databases for both newer ethanol-preserved samples and achieved formalin-fixed, IDA-preserved samples. The reliability and reproducibility of metabarcoding within pelagic samples provide evidence for using diversity as an indicator for ecosystem and Good Environmental Status monitoring. We used traditional methods alongside metabarcoding, to develop further evidence for indicators and the state of North Sea ecosystem health and monitoring. 1Newcastle University, UK 2023/08/10 (12:00-12:15)
Satellite data towards the UN Ocean Decade Challenges: case studies and tutorials from EUMETSAT 1Hayley Evers King, 2Benjamin Loveday, 3Vinca Rosmorduc, 4Aida Alvera-Azcarate, 5Vittorio Brando, 6Ana Ruescas, 1Rob Roebeling Poster Session 1 The UN Decade of Ocean Science for sustainable development has proposed 10 challenges for collective impact. The challenges address marine pollution, biodiversity, sustainable food production and ocean economy, climate change, resilience to ocean hazards, ocean observation, digital representation of the ocean, capacity development, and humanity’s relationship with the ocean. In a series of use case stories, we will show how data provided by EUMETSAT, and that provided by Copernicus missions and services, can support meeting these challenges. From climate scale observations of sea-level change to estimating ocean carbon pools; from providing easily accessible data visualization tools to in-depth training courses; data and activities provided by EUMETSAT are able to contribute to a more sustainable future for our oceans and thus for all of us, whether we depend on oceans directly or indirectly. Each case will include a web-based story, links to further information on data and opportunities through EUMETSAT, as well as a hosted Jupyter Notebook showing an example of the relevant data in use. In this presentation we will summarize the series of cases, released over the course of 2022 and 2023, and provide a live demonstration of some example applications of these notebooks in action. 1European Organisation for the Exploitation of Meteorological Satellites, Germany; 2Innoflair UG, Germany; 3Collecte Localisation Satellites, France; 4Azcarate, University of Liege, Belgium; 5CNR, Institute for the Marine and Coastal Environment, Italy; 6Brockmann Consult GmbH, Germany 2023/08/09 (17:30-19:00)
Ocean Reflections: Over 50 years of scientific excellence in marine science 1Heather A Bouman Oral Session 3: Marine Optics & Ocean Colour Professor Trevor Charles Platt, FRS, FRSC, made fundamental contributions to a wide range of research areas from determining the caloric content of plankton to the quantifying of global production using earth-orbiting satellites. Trevor was one of the first oceanographers to recognise the potential of ocean colour imagery as a tool to understand large -scale biological processes. Together with Shubha Sathyendranath, he was the first to devise a method to model marine primary production from ocean-colour images and has since used ocean-colour radiometry to derive ecological indicators for a variety of applications, such as fisheries research and marine management. This talk provides a short biographic sketch of how the work of Trevor and his collaborators led to transformative breakthroughs in our understanding of how energy is transferred within food webs and how pelagic systems are structured. This talk will highlight some of Trevor’s major scientific achievements and those of the students, postdoctoral researchers, and early career scientists that he mentored over the years. 1University of Oxford, UK 2023/08/10 (09:00-09:30)
Variability of mackerel fish catch and remotely-sensed biophysical controls in the eastern Pemba Channel 1Hellen Joseph Kizenga, 2Fatma Jebri, 3Yohana W. Shaghude, 4Dionysios Raitsos, 2Meric Srokosz, 2Zoe Jacobs, 5Francesco Nencioli, 3Mwanahija Shalli, 3Margareth S Kyewalyanga, 2Ekatarina Popova Poster Session 2 Advances in satellite remote sensing of environmental perturbations have become important in understanding variations of ocean productivity and small pelagic fish catches. In the East African region, the eastern Pemba Channel (Tanzania) represents a hotspot area, for a variety of marine species including small pelagics. This study examines the links between mackerel fish catch and the environmental oceanographic parameters over the period 2012-2018. The fisheries catch data is a rare dataset supplemented by qualitative information from interviews with local stakeholders. The biophysical parameters assessed include the remotely-sensed chlorophyll-a and Sea Surface Temperature (SST), together with Mixed Layer Depth data from the NEMO ocean model. We show that seasonal and monthly variations in mackerel landings are positively (negatively) correlated with Chlorophyll-a (SST) with time lags, interannually these relationships remain valid. Enhanced productivity is observed during the southeast monsoon, accompanied by deepening of the mixed layer. We conclude that upper ocean mixing contributes to the observed enhanced productivity along with other environmental factors leading to high fish catches especially during the southeast monsoon season. Additionally, we show how our results can be applied in the management of the mackerel resource in the Pemba Channel. 1Institute of Marine Sciences of the University of Dar es Salaam, Tanzania; 2National Oceanography Centre, Tanzania; 3Institute of Marine Sciences, Tanzania; 4National and Kapodistrian University of Athens, Greece; 5Plymouth Marine Laboratory, UK 2023/08/10 (17:00-18:30)
Winter convective mixing couples primary production and nitrogen fixation with nutrient supply in the Arabian Sea 1,2Himanshu Saxena, 1,2Deepika Sahoo, 1Sipai Nazirahmed, 1,2Deepak Kumar Rai, 1Mohammad Atif Khan, 1Niharika Sharma, 1Sanjeev Kumar, 1Arvind Singh Poster Session 1 Primary production and nitrogen fixation influence marine carbon fluxes and the Earth’s climate. Yet, their geographical coverage is limited and controlling environmental parameters remain unclear. Despite its biogeochemical recognition, the northern Indian Ocean remains understudied, and particularly there is barely any experimental work on nitrogen fixation in this region. We performed on-deck tracer incubation experiments to measure primary production and nitrogen fixation rates from the two spatially and physico-chemically contrasting regions of the Arabian Sea: the colder and nutrient-rich surface waters in the northern region owing to winter convection, and warmer and nutrient-poor surface waters in the southern region unaffected from winter convection. Satellite-derived air temperature, sea surface temperature and salinity clearly delineated the convection-affected region in the Arabian Sea, and a positive influence of this vertical mixing was seen in satellite-derived chlorophyll a data. We found substantially higher primary production and nitrogen fixation rates at the surface of convection affected regions due to convective mixing driven supply of phosphate and iron from the underlying suboxic waters, whereas in the convection unaffected regions the rates were appeared to be limited by the availability of iron. Nitrogen fixation supported up to 11% of primary production. Our comparative analysis with the previous studies indicated a decrease in primary productivity in the Arabian Sea within the last two decades, which was attributed to the increased stratification and a consequential decrease in convective mixing during the winter monsoon within the last two decades in the Arabian Sea. 1Physical Research Laboratory, Ahmedabad, India; 2Indian Institute of Technology Gandhinagar, Gandhinagar, India 2023/08/09 (17:30-19:00)
Investigating the influence of mesoscale eddy dipoles on phytoplankton biomass and primary production in the North Atlantic 1Hong Wuyi Zhao Poster Session 2 Phytoplankton are regarded as a critical component of the planetary ecosystem, owing to their profound influence on Earth’s biogeochemical cycles and food webs. In the context of climate change, understanding how phytoplankton are responding to the physical environment is key to predicting future changes in ocean biogeochemistry. Mesoscale eddies play a major role in material transport and energy exchange in the ocean. Despite their prominent role in ocean physics, relatively little is known on their influence on phytoplankton distributions and productivity, primarily due to difficulties in sampling of subsurface waters of the eddies. However, that is changing, owing to the increasing deployments of ocean robotic platforms, such as Biogeochemical (BGC) Argo floats, in regions like the North Atlantic. This study will harness these new ocean robotic observations, together with satellite data and new tools capable of separating surface (seen by satellite) and subsurface (seen by BGC-Argo) phytoplankton biomass and primary production, with the goal to improve our understanding of the influence of mesoscale eddies of phytoplankton and ocean carbon cycle. Key words: mesoscale eddy dipole; North Atlantic Ocean; chlorophyll; primary production; ocean carbon 1The University of Exeter, UK 2023/08/10 (17:00-18:30)
Monitoring of essential oceanographic variables (EOVs) in Tunisia’s coastal water: Towards sustained observations of met-ocean and biochemical EOVs 1Houssem Smeti, 2Malika Bel Hassen, 1Moncef Boukthir Poster Session 2 Sustained observations of EOVs, including meteorological, oceanographic and biogeochemical parameters are the pillar of a successful science-based monitoring of water quality in coastal and marine environments. A moored data-buoy deployed off the city of Mahdia and was set to autonomously sample the surface layer of the water column for several meteorological, hydrodynamic and biochemical variables. Data were collected hourly. Raw data were quality controlled and time-series analysis methods such as de-trending, harmonic and empirical orthogonal functions analyses were applied to sea level, current and wind data. An acoustic current-meter was deployed on the seabed and measured current module and direction. In water off Mahdia, maximum tidal current speed reached 24 cm/s with a North-East prevailing direction in the summer-fall period, during which northeasterly winds are dominant. Maximum wind speed reached 25 km/h (13.5 knot). Maximum value of dissolved oxygen concentration reached 9.8 mg/l and on average was 4.3 mg/l. The main tidal constituents obtained from sea level and current analysis were the lunar and the solar semi-diurnal constituents, M2 and S2. The average wave peak period was Ts = 13s. The hydrodynamics of the study region is dominated by a moderate tidal current flowing southward along the coastline, sustained by north-western wind. Several Tunisian coastal regions, such as Mahdia, are important fishing grounds and provide a variety of other services (e.g., aquaculture, tourism). We show that our moored data-buoy can deliver concurrent time-series data in near-real-time, allowing to monitor meteorological, hydrodynamic and water quality parameters. 1University of Tunis, Tunisia; 2Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali, Italy 2023/08/10 (17:00-18:30)
Phytoplankton Bloom Events in the Baltic Sea - Usefulness of Satellite Data for Monitoring 1Ian-Andreas Rahn, 1Kersti Kangro, 1Krista Alikas, 2Andres Jaanus Poster Session 1 Phytoplankton bloom events are increasingly prevalent in the Baltic Sea. Bloom events can be harmful for the environment and are a public health risk in coastal areas. The goal of the current research was to analyse the applicability of satellite data for assessing phytoplankton bloom parameters during spring and summer bloom events in coastal areas. 20 areas of interest were under study from 2016-2022. Because the blooms vary in their species composition, two separate methods were used in the assessment. The CyaBI (Cyanobacterial Bloom Indicator) for assessing bloom events during summer (June-August) and the Phytoplankton spring bloom intensity index during spring (April-May). Data was collected from Sentinel-3 A/B OLCI and processed by Case-2 Regional CoastColour (C2RCC) processor. Additionally, another algorithm was used to assess the cyanobacterial bloom events in the summer, the Maximum Chlorophyll Index (MCI). Phytoplankton concentrations were derived from C2RCC processor chl-a values. Validation of C2RCC showed poor correlation with in-situ data (R2<0.5). However, the regional differences in bloom index values matched the expected results from in-situ data. MCI algorithm was validated against in-situ cyanobacterial data showing poor results (R2<0.4). Environmental assessment results showed high phytoplankton concentrations in more enclosed coastal areas, such as Pärnu Bay and Matsalu Bay, and lower or no bloom events in open coastal regions, such as Kihelkonna Bay. Cyanobacterial blooms are also more prevalent in Pärnu Bay and less common in Soela Strait. More research is needed to develop suitable algorithms for the purposes of monitoring phytoplankton blooms in coastal areas. 1University of Tartu, Estonia; 2Estonian Marine Institute, Estonia 2023/08/09 (17:30-19:00)
Effects of droughts on phytoplankton biomass and suspended particulate matter in the Dutch coastal shelf 1Isabel Leidiany de Sousa Brandao, 1Johan van der Molen, 1Daphne van der Wal Poster Session 1 The effects of climate change on water quality on coastal shelves during periods of severe drought are largely unknown. In this study, we investigated the response of chlorophyll-a (Chl-a) and suspended particulate matter (SPM) concentrations to river outflow on a five-year time series of Sentinel-2A Multispectral Instrument (MSI) satellite data in the port of Rotterdam and adjacent North Sea. We used the ACOLITE processor to correct for atmospheric effects before retrieving chlorophyll and SPM from the Sentinel-2 MSI data. Chla was retrieved using the semi-analytical algorithm of GONS, which was calibrated for turbid waters, while for SPM we considered the widely validated NECHAD algorithms. We considered annual and seasonal variability of Chl-a and SPM in relation to wind speed, river discharge, and nutrient concentrations, as well as drought climate indices, to capture the effects of dry periods on water quality. The SPM and Chl-a composites depict seasonal variations in these two variables along the Dutch coastal shelf. While the Standardized Precipitation-Evapotranspiration Index (SPEI) recorded 2018 and 2019 as the driest years of our study period, we were unable to clearly depict these variations in interannual composites of Chl-a and SPM concentrations in our preliminary results. 1Royal Netherlands Institute for Sea Research (NIOZ), Netherlands 2023/08/09 (17:30-19:00)
Observing low-oxygen-adapted phytoplankton in the eastern tropical North Pacific using a Biogeochemical Argo float 1Isabelle Cox, 1Robert Brewin, 2,3Giorgio Dall’Olmo, 1Katy Sheen, 3Shubha Sathyendranath, 4Rafael Rasse, 5Osvaldo Ulloa Poster Session 2 Phytoplankton have evolved to thrive in a range of habitats, with some occupying extreme environment, such as very low-oxygen and low-light waters in the eastern tropical North Pacific (ETNP). Located deep within the upper water column, this phytoplanktonic community often eludes observations when using conventional platforms (e.g., ships and satellites). Using data collected by an ocean robotic platform, Biogeochemical Argo (BGC Argo) float, over a 5-year period (2016-2021) we study the dynamics of this unique phytoplanktonic community in the ETNP. We extend the two community model of Brewin et al (2022) to a three community model, designed to partition the contributions of three communities (C1, C2, C3) to vertical profiles of chlorophyll-a (chl-a) and backscattering. We find that C3 has a low chl specific backscattering relative to C1, while contributing significantly to integrated stocks of chlorophyll biomass, at around 41% of integrated chl-a, and around 30% of integrated particulate backscattering (after removing a background backscattering signal). The peak biomass of C3 (at around 100m) is lower than that of C2 (at around 60m), yet C3 makes similar contributions to integrated stocks, because it has a broader peak. In relation to C1 and C2, C3 thrives in a lower temperature, higher density, lower light, lower oxygen, and higher saline habitat. This work illustrates how BGC-Argo floats, in combination with simple conceptual models, can be used to observe the dynamics of unique communities of phytoplankton in extreme environments. Projected climate-driven changes to oxygen minimum zones adds urgency to studying the response of these communities. 1University of Exeter, UK; 2National Institute of Oceanography and Applied Geophysics – OGS,I taly; 3Plymouth Marine Laboratory, UK; 4Centre national de la recherche scientifique, France; 5University of Concepción, Chile 2023/08/10 (17:00-18:30)
Distribution of Leptospira sp. in the waterbodies of a tropical region and the incidence of disease outbreaks 1Jasmin C Anas, 4Sara Irum, 8Arathi M, 5Vinay Bhat, 1Ranith R, 6Abdulaziz Anas, 1,2Nandini Menon, 7Grinson George, 2,3Shubha Sathyendranath Poster Session 2 Leptospirosis is a water-associated, zoonotic, and often-ignored disease, affecting more than a million people worldwide yearly, with a five percent fatality rate. The disease is caused by a Gram-negative bacterial pathogen Leptospira sp., which colonizes in kidneys of rodents and are excreted into the environment through urine. The disease is wide-spread in areas where environmental hygiene is poorly maintained, and humans encountering contaminated water are prone to infection. Our study hypothesizes that frequent rain and flooding increase the microbial contamination in the water bodies and low-lying areas of Kerala, India, during monsoon season, which might explain the increase in the number of reported cases of the disease during monsoons. Water samples collected from the canals and coastal waters of areas around Vembanad Lake along the southwest coast of India were analysed for the presence of Leptospirosis sp. The molecular technique based on PCR amplification of 16srRNA and pathogenic gene lipl32 was used for the detection of pathogen. The result indicates that both saprophytic and pathogenic Leptospira are prevalent in the unhygienic areas of canals, and that this pathogen reaches coastal waters through connected water bodies. Our results point to the need for continuous monitoring of water bodies and for demarcating areas contaminated by pathogenic Leptospira to avoid or at least minimize the incidence of disease outbreaks. 1 Nansen Environmental Research Centre (India), Kochi, 682506, India; 2Trevor Platt Science Foundation, Kochi, 682 018, India; 3Plymouth Marine Laboratory, Plymouth, Devon, UK; 4Sir Syed Institute for Technical Studies, Kannur, 670 142, India; 5Enfys Lifesciences Pvt. Ltd. Kochi, 683 578, India; 6CSIR-National Institute of Oceanography, Regional Centre Kochi, 682 018, India; 7ICAR-Central Marine Fisheries Research Institute, Kochi, 682018, India; 8Kerala university of Fisheries and Ocean Studies, Kochi, 682 506, India 2023/08/10 (17:00-18:30)
Coupling AMT in situ data of ocean biogeochemical variables, surface to photic zone, with SRS data of the sunlit ocean, to predict sub-surface variables from RS data 1Jim Aiken, 1Graham Quartly, 1Bob Brewin, 1Arnold Taylor Andy Rees, 1John Stephens Poster Session 1 Since 1995, the Atlantic Meridional Transect (AMT) has acquired data of oceanic physical and biogeochemical variables in the Atlantic Ocean, 50N to 50S. Core objectives focus on impacts of global warming, climate change on marine ecosystems, bio-optical properties, air-sea exchange of CO2, other bio-active gases/particles. Satellite Remotely Sensed (SRS) data of ocean biogeochemical variables are available daily, globally, at resolutions of tens of km; merged data sets from several satellite sources e.g. CCI are used. An AMT goal is to couple AMT and SRS data, quantifying biogeochemical variables through the water column. AMT covers several BGC provinces: N Atlantic temperate gyre (NATG); N Atlantic subtropical gyre (NAG); Equatorial upwelling zone (EZ); S Atlantic subtropical gyre (SAG); S Atlantic temperate gyre (SATG) and upwelling zones off the coasts of N & S Africa and S America. The STGs are permanently stratified; the temperate gyres seasonally stratified in spring/summer and mixed to below the photic zone in autumn/winter, AMT cruises cover 4 seasonal modes, with different relationships between BCG variables. The modes are: Boreal Fall; Austral Spring; Austral Fall; Boreal Spring. This paper continues research on the N & S Atlantic STGs that are quasi-stable, with seasonal variability. 1Plymouth Marine Laboratory, UK 2023/08/09 (17:30-19:00)
Climate variability shifts in the vertical structure of tropical oceanic phytoplankton 1Johannes J Viljoen, 1Xuerong Sun, 1Robert J W Brewin Poster Session 2 Marine phytoplankton contribute to around half of planetary primary production, supply energy to the marine ecosystem and are essential to global climate. Despite their importance, uncertainties exist in how they are responding to climate variability. So far, studies have focused on understanding changes in phytoplankton biomass (surface or column integrated), physiology, phenology, biogeography, community composition and production, with little emphasis on vertical structure. Here, we apply a conceptual model that partitions a vertical profile of phytoplankton biomass into two communities – one in the surface mixed layer and the other in the subsurface, below the mixed layer – to a long-term time series in the Sargasso Sea. Results show contrasting seasonal and multidecadal trends in the two communities. Both communities respond to climate variability (Atlantic Multidecadal Oscillation) by modifying their physiology (carbon to chlorophyll-a ratio) rather than biomass (carbon), but the surface community acclimates more tightly than the subsurface, which remain relatively stable during rapid warming events. We show climate variability shifts the vertical structure of tropical oceanic phytoplankton. Considering satellite remote-sensing can only view the surface layer, we require sustained subsurface measurements of phytoplankton at global scales using multiple platforms, to fully understand how phytoplankton are responding to climate change. Currently, this can only be achieved using a sustained global array of robotic platforms. 1Centre for Geography and Environmental Science, Department of Earth and Environmental Science, University of Exeter, Cornwall, UK 2023/08/10 (17:00-18:30)
Estimate of primary production in case-I waters using GOCI-I/II (GK-2B) combined with AMI (GK-2A) data 1Jongkuk Choi, 1Deuk Jae Hwan, 1Seonju Lee, 1Kyeong-Sang Lee Poster Session 1 Primary production (PP) is doing a key role in energy circulation in the ocean environment, particularly regulating the food cycle of marine ecosystem. Many attempts have been applied to estimating PP in the ocean surface including ship-board measurement in collected water samples, which had limitations in terms of temporal and spatial resolutions. Here, we tried to map PP in case-I waters in the South Pacific Ocean around Korea-South Pacific Ocean Research Center using geostationary ocean color imager II (GOCI-II) onboard the GeoKompsat-2B (GK-2B) combined with advanced meteorological imager (AMI) onboard the GK-2A. The result was compared with that from highly productive Korean coastal waters induced by GOCI-1. We also examined the variations in the PP in the study area at daily base. To calculate PP in the study area, sea surface chlorophyll-a concentration, the depth of the euphotic zone and the photosynthesis available radiation (PAR) on the sea surface has been derived from GOCI-I/II. Sea surface temperature (SST) provided by the AMI sensor has been also applied to the mapping of PP in the study area. From those satellite-based factors, we examined the temporal variations in the productivity in the South Pacific waters and the differences between the study area and the Korean coastal waters. 1Korea Institute of Ocean Science and Technology, South Korea 2023/08/09 (17:30-19:00)
Assessment of Chlorophyll-a Remote Sensing Algorithms based on Sentinel-3B data in the eastern Algerian Coast (SW Mediterranean Sea) 1Khadidja Wissal Abdallah, 2Romaissa Harid, 3Aicha Djabourabi, 2Fouzia Houma-Bachari Oral Session 3: Marine Optics & Ocean Colour Although the estimation of biological components, such as chlorophyll-a (Chl-a) using satellite imagery has shown significant progress, the validation of the remotely sensed data in coastal regions is revealed as a necessity due to their complex optical properties. This study was carried out on the eastern Algerian coast to evaluate the performance of Sentinel-3 data for the estimation of Chl-a. The two Chl-a products incorporated in the level-2 of Sentinel-3B images (Chl-a NN and OC4Me) as well as six other algorithms (OC5, OC6, MedOC4, G2B, 2B.OLCI, and 3B.OLCI) were compared to the measured Chl-a using a spectrophotometer at fixed locations (44 valid match-ups). The results reveal the strong performance of the Chl-a NN product based on a neural network (r = 0.973, RMSD = 0.656, BIAS = 0.353, MAE = 0.395), followed by the blue-green algorithms (OC4Me, OC5, OC6, and MedOC4), whereas the near-infrared (NIR) algorithms (2B.OLCI, 3B.OLCI, and G2B) show underwhelming performance and very poor prediction of the Chl-a concentration (negative values). Even though the OC4Me has the best correlation (r = 0.982), it also has a highest RMSD, BIAS, and MAE (1.264, 0.580, and 0.628, respectively) compared to the Chl-a NN, which demonstrates the best fit and outperforms the other bio-optical methods for the estimation of the Chl-a. This product based on Sentinel-3 data can be successfully integrated into the monitoring programs for the Algerian coastal waters. 1Chadli Bendjedid University, El Tarf, Algeria; 2Ecole Nationale Supérieure des Sciences de la Mer et de l’Aménagement du Littoral, Algeria; 3Chadli Bendjedid University, Algeria 2023/08/10 (10:00-10:15)
Distribution of Vibrio spp in a tropical lake influenced by monsoon and anthropogenic activities 1Kiran krishna, 1Anas Abdulaziz, 2Nandini Menon, 3Grinson George, 4Shubha Sathyendranath Poster Session 2 Salinity is known to be a major factor influencing the distribution of Vibrio spp. in global estuaries. The current study discusses the dynamics of Vibrio spp. in Vembanad lake situated along the southwest coast of India. Towards this end, we monitored physicochemical (Salinity, temperature, Turbidity, DO, pH, Silicate, Phosphate, Nitrate, Nitrite, Ammonia,) and biological (Chlorophyll, Phytoplankton abundance, Free living vibrios) variables from 13 stations of the study area in a ~20-day interval for a complete year (2018-2019). Vibrio spp. & Escherichia coli were enumerated using quantitative real time PCR. The entire Vembanad lake remains freshwater dominated during the wet period (June - August and October -November). whereas during the dry period (May, September, January-March), the lake was divided in to brackish- (northern region of the lake) and fresh- (southern region of lake) water dominated regions. Salinity did not show any influence on the abundance of Vibrio spp. in Vembanad lake during the wet period, while a significant (p<0.001) but weak (r=0.32) relation was observed during the dry period. Statistical analysis (two-way ANOVA) of the data (n=193) attributed this to the lack of spatial variability in the distribution of Vibrio spp. Anthropogenic activities, including industrial and sewage discharge, shipping, tourism, agriculture, and fishing around Vembanad lake also influence the local distribution of Vibrio spp in Vembanad lake. This was evident in some stations where the distribution of Vibrio spp showed correlation with turbidity (r=0.30, p<0.01) and Escherichia coli, the indicator of faecal contamination (r=0.21, p<0.05). Multiple Linear Regression (MLR) analysis showed that salinity, turbidity, ammonia, and E. coli could explain 74.0 % (p<0.01) of the spatial average distribution of Vibrio spp in Vembanad lake. Similarly, 82.4% (p<0.001) of the average temporal distribution of Vibrio spp could be explained by the fluctuations in the concentrations of salinity, nitrite, and phosphate. Principal component analysis indicates that anthropogenic inputs such as ammonia from nonpoint sources make the physio-chemical and biological settings in the Vembanad lake complex. The predictability of water-associated pathogens such as Vibrios may be difficult in such scenarios. 1 CSIR-National Institute of Oceanography, Kochi-18; 2Nansen Environmental Research Centre (India), Kochi, 682506, India; 3ICAR-Central Marine Fisheries Research Institute, Kochi, 682018, India; 4Plymouth Marine Laboratory, Plymouth, Devon, UK 2023/08/10 (17:00-18:30)
The Double Diffusion of The Western Pacific Water Masses 1Lamona Bernawis, 1Faisal A R Abdullah, 2Rahaden B Hatmaja, 3Muhamad Nur Poster Session 2 This study examines the impact of the double diffusion on the water mass composition and motion in the western Pacific Ocean. The time series observational CTD data of this study is from 1967 to 2019 at 137°E, 3°N - 34°N, all winters and summers. To quantify the activity of double diffusion, this study calculated the density ratio, -hence the Turner angle to define whether it is Salt Finger, Diffusive Convection or Statically Stable. The results show that the salt finger is found mostly at the upper boundary layer of intermediate water (NPIW) and diffusive convection at the surface and deeper water mass. The active salt finger in NPIW is about 0.5 to 7 % near the equator and at the depth of the NPIW and NPTW interleave, the total percentage salt finger is about 50% along the 137°E line. Southward inclination of NPIW core is detected from 20 to 7°N. The velocity (along 20°N to 7°N) of the potential temperature advection and of the salinity advection is calculated in turbulence scheme and Salt Finger scheme. The result is SF scheme is more likely to cause the advection velocity. The NPIW tongue and NPTW core is shifting southward within 53 years of observation. More to mention is that the Salt Finger convection is increasing during the past 53 years. 1Institut Teknologi Bandung, Indonesia; 2National Research and Innovation Agency, Indonesia; 3Sriwijaya University, Indonesia 2023/08/10 (17:00-18:30)
The Nansen Centers, Trevor Platt and Shunha Sathyendranath – scientific association for capacity building 1Lasse H Pettersson, 1Annette Samuelsen, 1Tore Furevik, 2Ajith Joseph K, 2Nandini Menon N Poster Session 1: International collaboration and capacity building The six international Nansen Centers and the Nansen Scientific Society (NANSI) have had long lasting scientific collaboration with Prof. Trevor Platt and Dr. Shubha Sathyendranath, focusing on marine ecosystem research and capacity building. The collaboration includes the international symposia on ‘Societal Applications in Fisheries and Aquaculture using Remote Sensing Imagery (SAFARI)’ at Kochi in 2010 and 2018. Several interdisciplinary summer research schools have been organized together with and at the Nansen Centers in Bergen, Kochi, Dhaka and Cape Town. Surrounding the Indian Ocean, the collaboration with the Nansen-Tutu Center for Marine Research (NTC) at University of Cape Town is close. The INDO-MARECLIM project (2012-2015), coordinated by NERCI, was the first European Commission funded project co-ordinated by any Indian institution. INDO-MARECLIM organised joint scientific workshops and winter research schools for young Indian, Asian and European scientists, and students on the interactions between climate change, marine ecosystem, and coastal zone management. The European partnership of NERCI was also expanded with four new European associated partners, including Plymouth Marine Laboratory (UK). A working group on marine primary production (PP) to standardise methods and increase data collection in India, was established. The award of Jawaharlal Nehru Science Fellowship to Platt in 2015 enhanced the co-operation further with NERCI. Platt´s establishment a multi-disciplinary network of scientists from India, Brazil, UK and Norway linking EO, water quality and human health, to meet the UN-SDG targets 3, 6, 13 and 14, will be maintained through Trevor Platt Science Foundation (TPSF). 1Nansen Environmental and Remote Sensing Center (NERSC); 2Nansen Environmental Research Centre (India) 2023/08/09 (17:30-19:00)
Application of CCGAN for gap filling of surface chlorophyll-a concentration - an Adriatic case study 1Leon Ćatipović, 2Hrvoje Kalinić, 1Tomislav Županovic, 2Shubha Sathyendranath, 2James Dingle, 2Thomas Jackson, 1Frano Matići Poster Session 1 This abstract is the presentation of submitted work currently under review in Neural Computing and Applications journal. Satellite detection of surface chlorophyll-a concentration (chl-a) is prone to frequent gaps due to various atmospheric and sea surface conditions. These gaps diminish the usefulness of the entire sea-viewing satellite missions. During the past two decades various methods to estimate the missing data have been tested and tried. Generally, these methods are usually applicable to other gap-plagued satellite variables, e.g. sea surface temperature (SST). However, unlike SST, (chl-a) has seen much less application of neural-network-based methods for reconstruction. This paper presents a novel application of Context-Conditional Generative Adversarial Network (CCGAN) for gap reconstruction in satellite-derived chl-a in the Adriatic. The CCGAN has been modified to take into account the structural composition of data in order to improve the reconstruction efforts. CCGAN treats the input satellite data as multispectral images, allowing for addition of various proxy variables, such as SST and bathymetry, in order to further improve the reconstruction accuracy. While complete low-resolution data is still required to maximise reconstruction accuracy, this first-iteration approach has provided relatively high reconstruction accuracy and a footing for further development and testing of the method. 1University of Split, Croatia; 2Plymouth Marine Laboratory, UK 2023/08/09 (17:30-19:00)
The Nf-Pogo Capacity Development Programme And Alumni Network 1Lilian Krug, 1Fiona Beckman, 1Sophie Seeyave Poster Session 1 The Nippon Foundation (NF) and the Partnership for Observation of the Global Ocean (POGO) joint capacity development programme aims to develop global advanced scientific understanding of the ocean through professional training opportunities, expanding worldwide capacity for conducting sustained ocean observations, data collection, analysis and management, and interpreting the scientific results for the benefit of society. The programme is conducted through research fellowships and scholarships for i) training at an advanced oceanographic institute, exposing trainees to state-of-the-art equipment and techniques, ii) regional trainings in developing countries institutes, tailored to the working conditions and resources of the region, and iii) shipboard training, making use of spare berths on board planned research cruises, or running dedicated training cruises on transiting ships. Since 2004, NF-POGO has offered training to nearly 500 early-career ocean professionals from 72 countries, mainly with emerging economies. Many of these past trainees now hold high-level positions in oceanographic institutes, universities, and government ministries. Aspiring to maximize the benefits from the training and to strengthen networking among trainees, in 2010 NF-POGO created the NF-POGO Alumni Network for the Ocean (NANO). NANO maintains a website, social media and produces a biannual newsletter (currently in its 22nd edition) with updates on the Network’s activities and alumni’s professional achievements. It also provides support to outreach conducted by members in their countries and joint, international research projects. Since 2018, NANO supports the development of a low-cost temperature sensor aimed at citizen science (SAGITTA) and an alumni-led network of 36 time-series stations in 18 countries, which monitor a common set of essential ocean variables (NANO-DOAP). 1Partnership for Observation of the Global Ocean (POGO), USA 2023/08/09 17:30-19:00)
Beyond biomass: the optics of phytoplankton photophysiology 1Lisl Lain, 1Sandy Thomallan Oral Session 2: Marine Optics & Ocean Colour Chlorophyll a is appetisingly green and the swirling patterns of its concentrations across the global oceans make it an attractive target for satellite radiometry. Useful too, of course, as an indicator of phytoplankton abundance and hence biomass estimates for use in carbon-climate models addressing some of the most important questions we face today. In the Southern Ocean (SO) an increasing trend in chlorophyll-a concentration is observed, typically attributed to increased productivity. But could there be something else at play? Variability in intracellular chlorophyll a is one of the better understood adaptive processes of phytoplankton physiology, and we show how it impacts upon the phytoplankton optical signal, leading to a counterintuitive quandary when chlorophyll a drives one’s understanding of how biomass is revealed in the optics. Using the Equivalent Algal Populations model of phytoplankton Inherent Optical Properties (IOPs) to integrate our understanding of physiological and optical processes, we explore varying interpretations of biomass from satellite and in situ data, including the utility of a carbon-specific IOP model. 1Council for Scientific and Industrial Research, South Africa 2023/08/09 (14:15-14:30)
Sensor-agnostic deep learning of coastal ocean chlorophyll 1Lloyd Hughes, 2Marié Smith, 2Lisl Lain, 1Devis Tuia Poster Session 1 Coastal waters support 90% of marine species and are areas of key socio-economic importance to more than three billion people who rely on coastal biodiversity for food, aquaculture, and tourism. However, increased coastal ocean usage and climate change have led to harmful algal blooms (HABs) occurring more frequently and severely. The Southern Benguela system is a prime example, with a yessotoxin-producing bloom in 2019 resulting in millions of abalone stock dying and an estimated financial loss of $33 million. The accurate reporting of coastal ocean chlorophyll-a (Chl-a) concentration (a proxy for phytoplankton biomass) is crucial to our ability to better detect, monitor and understand these HAB events. Existing Chl-a algorithms have limitations, particularly in waters with very-high or very-low phytoplankton biomass (<1 to >100 mg/m-3), such as the southern Benguela and other upwelling systems. Thus it is common practice to develop regionally specific algorithms (Smith & Bernard, 2018). Due to the complexity of developing these models, they are often designed to work with a single imaging platform, which limits their availability and usability for consistent long-term monitoring. To address these limitations, we propose a deep learning-based Chl-a model that can provide regionally accurate Chl-a estimates across multiple remote sensing platforms (Sentinel-3, VIIRS, MODIS, etc.). The model enables robust, consistent, and high-frequency monitoring of potential HAB events by exploiting temporal heterogeneity and spectral similarities of various platforms. This leads to an improved understanding and potential mitigation of the impacts of HABs on coastal ecosystems and communities. 1École Polytechnique Fédérale de Lausanne (EPFL), Switzerland; 2Council for Scientific and Industrial Research (CSIR) in South Africa 2023/08/09 (17:30-19:00)
Comparative Analysis of the Chlorophyll-a of the MODIS-AQUA Sensor with data in situ during the Cruise 2018-0204 1Luis Escudero, 1Xan Xu, 1Jesus Ledesma Poster Session 1 Coastal waters support 90% of marine species and are areas of key socio-economic importance to more than three billion people who rely on coastal biodiversity for food, aquaculture, and tourism. However, increased coastal ocean usage and climate change have led to harmful algal blooms (HABs) occurring more frequently and severely. The Southern Benguela system is a prime example, with a yessotoxin-producing bloom in 2019 resulting in millions of abalone stock dying and an estimated financial loss of $33 million. The accurate reporting of coastal ocean chlorophyll-a (Chl-a) concentration (a proxy for phytoplankton biomass) is crucial to our ability to better detect, monitor and understand these HAB events. Existing Chl-a algorithms have limitations, particularly in waters with very-high or very-low phytoplankton biomass (<1 to >100 mg/m-3), such as the southern Benguela and other upwelling systems. Thus it is common practice to develop regionally specific algorithms (Smith & Bernard, 2018). Due to the complexity of developing these models, they are often designed to work with a single imaging platform, which limits their availability and usability for consistent long-term monitoring. To address these limitations, we propose a deep learning-based Chl-a model that can provide regionally accurate Chl-a estimates across multiple remote sensing platforms (Sentinel-3, VIIRS, MODIS, etc.). The model enables robust, consistent, and high-frequency monitoring of potential HAB events by exploiting temporal heterogeneity and spectral similarities of various platforms. This leads to an improved understanding and potential mitigation of the impacts of HABs on coastal ecosystems and communities. 1Instituto del Mar del, Peru 2023/08/09 (17:30-19:00)
Correlation of Harmful Algal Bloom Occurrence with Water Quality and Climate Characteristics in Malampaya Sound, Taytay, Palawan, Philippines 1Lutgardo Alcantara, 1Lota Creencia, 1John Roderick Madarcos, 1Karen Madarcos, 1Joel Sumeldan, 1Cristobal Cayetano, 1Arlene Avillanosa, 2Victoria Cheung Poster Session 2 It is well understood that in the last few decades, the Philippines has experienced an increase in the frequency and spatiality of paralytic shellfish poisoning due to harmful algal blooms (HABs). Despite this, the understanding of the effects of various water quality characteristics and climate factors at different spatial and temporal patterns in predicting the occurrence of HABs is still incomplete. The current research aims to understand the correlation of water quality characteristics and climate factors with the occurrence of HABs and to develop a predictive model. To accomplish these, we took seawater samples from June 2019 to March 2021 in Malampaya Sound Protected Landscape and Seascape in Palawan. We sourced the climate data from the National Aeronautics and Space Administration satellites such as sea surface temperature (SST), chlorophyll-a (Chl-a), rainfall, wind direction, and wind speed. Results showed that the presence of Chl-a in seawater detected by satellite remote sensing was very strongly correlated with the occurrence of HABs. On the contrary, the occurrence of HABs has a strong negative correlation with SST, Pb and wind direction. The environmental factors which favor the occurrence of HABs tend to occur during the dry season of the northeast monsoon and are influenced by Chl-a, SST, wind speed, ocean surface current, rainfall, salinity, Pb and P. The model can predict 87.4 – 89.5% of the variance in HABs occurrence. The result of this study contributes to a deeper understanding of the HABs phenomenon to predict and mitigate its sudden occurrence in the future. 1Western Philippines University, Philippines; 2University of Plymouth, UK 2023/08/10 (17:00-18:30)
Predicting abundance of jellyfish – an attempt to model distribution along Gujarat coast, India. 1Madhu Vettiyattil, 1Grinson George Poster Session 2 Gujarat, one of the leading states of India in marine fish production has sudden appearance of jellyfish blooms affecting fisheries and the occurrence of such events have increased tremendously in the last fifteen years, with average weight of jellyfish ranging from 200 to 1000 kg in a single haul in trawlers. An attempt was made to understand the spread of the blooms and factors affecting, was carried out using maximum entropy analysis. As input, the presence data from tows with geo-referenced data was used. Data from single-day and multiday fishing vessels operating off Veraval and Mangrol were used. For the distribution modelling, environmental data on chlorophyll, nitrate, phosphate, surface temperature, current velocity and salinity were used with maxent software. The background points for the forecasting included the entire east coast of the Arabian Sea. To populate the model for absence values, a total of 10000 background points were constructed. temperature, current velocity, and salinity were used along with maxent software. The distribution of jellyfish abundance along the Gujarat coast was predicted by the results of maximum entropy modelling. The results of the modelling approach and the important factors that can be considered as suitable for their prediction, along with the short comings using maximum entropy, and the possible advantages using real time remote sensing data, is discussed in the communication. 1ICAR- Central Institute of Fisheries Technology, India 2023/08/10 (17:00-18:30)
Estimation of Chlorophyll-a concentration in Diego-Suarez Bay using Aqua-MODIS Sensor 1Mahatsiaro Soavelo François, 2Amélie Landy Soambola , 3Charles Jean Lopes, 2Hermann Doris Benivary, 4Pascal Batch, 5W. Yohana Shaghude, 6Aina Ledon Nomenisoa, 1Faly Andriambahiny, 3Bachiry Aly Adouhouri Poster Session 1 Chlorophyll-a (Chl-a) is an photosynthetic pigment phytoplankton and important parameter to characterize the degree of eutrophication in water and healthy of marine ecosystem. It has become an important index for water quality evaluation and is also one of the important water quality parameters that can be directly retrieved by remote sensing method. In this study, Level-2 MODIS Aqua data and OC3M Chl-a inversion model are used to invert Chl-a in the Diego-Suarez Bay from January to December 2020. The spatial and temporal variations of Chl-a in the Diego-Suarez Bay are investigated, and the influencing factors are analyzed. The Wilcoxon test was used to compare dry and cold, and hot season, for the Chl-a concentration in this bay. Results illustrate that the variations of Chl-a in different bays of the Diego-Suarez have different trends. The concentration of Chl-a is related to the distance from the coast. The closer to the coast, the higher the concentration of Chl-a. From January to December 2020, the overall concentration of Chl-a in Diego-Suarez Bay show a downward trend, the seasonal variation trend is relatively small, and the variation of Chl-a in July is highest than that in April 2020. The concentration of chlorophyll-a showed that there were spatial and temporal variation in the Diego-Suarez. Generally, concentrations of chlorophyll-a were higher in South-West than North-East, South-East and North-West of Diego-Suarez Bay in dry and cold season, and it inversing on hot season. Dry and cold, and hot season, the Chl-a concentration in Diego-Suarez Bay were not significantly different (n=10, p>0.001) 1Ecole Doctorale Thématique :Nature, Structure de la Matière et Métrologie Nucléaire- Université d’Antsiranan, Madagascar; 2Faculty of Sciences, Department of Marines Sciences, Antsiranana University, Madagascar; 3Charles Jean Lopes, Centre Nationale de Recherche Océanographique (CNRO), Nosy Be, Madagascar; 4UMR MARBEC IRD, Ifremer, Université de Montpellier, CNRS; 5Institute of Marine Science, Zanzibar Tanzania; 6Institut Halieutique et des Sciences Marines, Université de Toliara, Madagascar 2023/08/09 (17:30-19:00)
Use of GIS and Remote Sensing for improved selection of suitable areas for cage fish aquaculture in Lake Victoria 1Makemie Mabula, 1Danielson Kisanga, 1Siajali Pamba Poster Session 2 The allocation of suitable sites is a common requirement for aquaculture activities, such as cage fish culture. However, delineating suitable sites requires expensive field surveys and simultaneous consideration of multiple and conflicting ecological, physical and socioeconomic factors. Since these factors vary in space, their integration is often complex and costly, especially when conventional field survey approaches are used. Geographic Information Systems (GIS) and Remote Sensing (RS) can be conveniently used to reduce the cost and labour needed to delineate suitable aquaculture sites while adhering to Ecosystem Approach to Aquaculture. In this study, GIS and RS approach is used to delineate areas with different suitability levels to support tilapia cage culture in the Mwanza Gulf of Lake Victoria (Tanzania). Our results show that only a small area, 5.10 km2, equivalent to 1.52% of the gulf, was the most suitable. The suitable area was 24.20 km2, approximately 7.44%. In addition, 64.47 km2 (19.82%) and 42.63 km2 (13.12%) were estimated as less suitable and unsuitable, respectively. The rest of the area (188.84 km2 or 58.06%) was “constrained” for cage aquaculture development. This method provides a fast and practical solution for identification of potential areas for sustainable cage culture. The results of this study will help decision-makers to devise holistic aquaculture plans in Tanzania. It is concluded that the GIS-RS could decrease extensive survey requirements during aquaculture site selection, especially in financial resource-limited countries such as Tanzania. We propose this approach be extended to other inland and marine waters. 1University of Dar es Salaam, Tanzania 2023/08/10 (17:00-18:30)
Application of Machine Learning Algorithms and Sentinel-2 Satellite for Improved Bathymetry Retrieval in Lake Victoria, Tanzania 1Makemie Mabula, 1Danielson Kisanga, 1Siajali Pamba Poster Session 1 Estimating bathymetric information is a key requirement for most aquaculture and navigation applications. The free and high-resolution satellite imageries can be used as convenient solutions to reduce the cost and labour needed for routine bathymetric measurements. In this study, we tested six algorithms; 1) the conventional Stumpf method, 2) Random Forest (RF), 3) Gradient Boosting Machine (GBM), 4) Extreme Gradient Boosting (XGB), 5) Neural Network (NNET) and 6) Support Vector Machine (SVM), to retrieve the water depth of the Mwanza Gulf of Lake Victoria from Sentinel-2 Satellite imageries. Each algorithm was trained and validated using in-situ depth points collected using echo sounders. The performance of the algorithms was measured in terms of coefficient of determination (R2), mean absolute error (MAE), the root-mean-square error (RMSE), Moran-I Index, and residual distribution. Of the six algorithms, the SVM produced the most accurate prediction (R2= 0.965, RMSE = 0.745, and MAE = 0.403) and proved to be the algorithm of choice for repetitive bathymetry calculation. 1University of Dar es Salaam, Tanzania 2023/08/09 (17:30-19:00)
The seasonal dynamics in plankton of Tanga coastal waters, Tanzania 1Margareth Kyewalyanga Poster Session 2 Several studies have reported on seasonal patterns of phytoplankton and zooplankton in different ecoregions; however, information on these plankton along the coastal waters of Tanga are limited. This study attempts to uncover and describe information related to abundance, distribution, and diversity of phytoplankton and zooplankton in the coastal waters of Tanzania, during the southeast monsoon (SEM) and northeast monsoon (NEM) seasons. Samples of phytoplankton, zooplankton and environmental variables were collected in the coastal waters of Tanga, from June 2019 to January 2021. One hundred and ninety-nine species of phytoplankton and thirty-two genera of zooplankton were identified. Although the abundance varied between the NEM and SEM seasons, Bacillariophyceae were abundant among the phytoplankton groups, and Copepods were the most abundant zooplankton in both seasons. The abundance variation in phytoplankton and zooplankton could be attributed to environmental variables, which varied significantly between seasons. The results suggest that high concentration nutrients during the SEM influences high plankton richness and diversity. 1University of Dar es Salaam, Tanzania 2023/08/10 (17:00-18:30)
Phytoplankton dynamics and phenology off southwestern Iberia: from chlorophyll-a to specific toxigenic groups 1Maria João Lima, 1Paulo Relvas, 1Ana B Barbosa Poster Session 1 Phytoplankton are dominant ocean producers, but some species represent a threat to ecosystems and human health. Yet, the comprehensive understanding and prediction of phytoplankton blooms, namely harmful algal blooms (HABs), remains a major challenge. This study aimed to evaluate phytoplankton variability patterns and phenology in a complex marine domain, off southwest Iberia, and identify underlying environmental drivers and predictors. Hydrographic and ocean physical variables were acquired from different sources (e.g., satellite remote sensing, in-situ observations), for a 6-year period (2014-2019). Chlorophyll-a concentration (Chl-a) was retrieved from ocean colour remote sensing. The abundance of toxigenic phytoplankton with contrasting functional traits, responsible for amnesic (Pseudo-nitzschia spp.) and diarrhetic shellfish poisoning (Dinophysis spp.), was accessed for coastal areas, from a public national database. Generalized additive models (GAMs) were used to develop region-specific empirical predictive tools. Over oceanic regions, Chl-a showed a unimodal annual cycle, with late-winter to early-spring maxima. Over slope and coastal areas, under stronger upwelling intensity, additional summer peaks were observed. This bimodal cycle was also observed for the diatoms Pseudo-nitzschia, whereas the dinoflagellate Dinophysis showed late-spring/summer maxima, under stratified conditions. GAMs explained 14% to 77% of Chl-a variance, and sea surface temperature, surface radiation, and mixed layer depth emerged as the most influential predictors. For HAB-taxa, model predictive skills were lower (Pseudo-nitzschia: 7-8%; Dinophysis: 21-54%), and Chl-a and riverine discharge were additional predictors. Current model developments, including the use of complementary environmental variables, species-specific abundance data, tailored remote sensing algorithms, and machine-learning modelling methods, might improve HAB model predictive skills. 1Centre for Marine and Environmental Research (CIMA), ARNET – Aquatic Research Network, University of Algarve 2023/08/09 (17:30-19:00)
Anthropogenic Activities and Lagoon Health: A case study on the Keta Lagoon of Ghana 1Maurice Oti Edusei, 1Edem Mahu, 1Priscilla Danso Poster Session 2 In this study, the trophic state of the Keta Lagoon complex and the relationship between Chlorophyll-A (Chl-a) and nutrient load were investigated. A detailed analysis of monthly and seasonal mean parameters across the water body was conducted. Statistical analyses were done to determine the relationship between Chl-a and the nutrients Total Nitrogen (TN) and Total Phosphorus (TP). The Carlson’s Trophic State Index was used to estimate the trophic state of the water body based on the concentrations of Chl-a, water transparency, and TP. The study found that there was a good correlation between Chl-a and TN loading, but a poor relationship with TP, which suggested that TN loading was the controlling factor for eutrophication. The Trophic State Index based on Chl-a estimation revealed that the lagoon was hypereutrophic, with a score of 60-64.9. The assessments by both the Trophic State Index (TSI) method and Plankton Index of Biotic Integrity (P-IBI) methods indicated that the lagoon was in eutrophic conditions at the time of the study. 1 University of Ghana, Ghana 2023/08/10 (17:00-18:30)
Seasonal changes in coastal circulation drive phytoplankton composition and algal blooms in southern Brazil 1Mauricio Almeida Noernberg, 1Samuel Francisco Alves Gonçalves, 1Luiz Laureno Mafra Jr. Poster Session 1 Physical forcing mechanisms regulate marine productivity, and their variability and impacts on marine ecosystems are particularly pronounced in coastal areas. Since August 2020, monthly sampling campaigns have been conducted at one 16m depth subtropical coastal station, located about 18Km from the southern Brazilian coast (25º40’S) on a broad (200Km wide) continental shelf surrounded by large estuaries. Essential ocean variables, absorption properties, the concentration of optically active substances, and the abundance and composition of microphytoplankton have been assessed along the water column. Preliminary data indicated marked seasonal oceanographic changes. The episodic influence of estuarine plumes and occasional high-energy events appear to be the main drivers affecting phytoplankton dynamics, ultimately triggering seasonal algal blooms in the area. In spring/summer, surface waters are usually occupied by salty, warm Tropical Water, with the eventual intrusion of the deeper, colder, nutrient-rich Central South Atlantic Water. In autumn/winter, shelf waters are mainly influenced by the less salty (~32), cold, and the nutrient-rich plume of the La Plata River, located southwards. Whereas large dinoflagellates such as Tripos muelleri, Tripos furca, and Tripos fusus were dominant in winter/early spring, diatoms like Coscinodiscus spp., Odontella spp., Thalassiosira spp., and Thalassionema nitzschioides were more abundant in summer. Nearly monospecific blooms were recorded in spring: Coscinodiscus cf. radiatus, in 2021 and the harmful, diazotrophic cyanobacterium Trichodesmium erythraeum, in 2020. Long-term monitoring of physical forcing and associated biological responses, as proposed here, is required to understand the variability of coastal productivity and to assess the impacts of human activities on ocean health. 1Federal University of Paraná, Brazil 2023/08/09 (17:30-19:00)
Microplastic contamination in Mud Spiny Lobster from the Northern Bay of Bengal 1Md Nabid Hashar, 1Md Shajjadur Rahman Poster Session 2 This research attempts to determine the degree of microplastic(MP) contamination in the Northern Bay of Bengal Mud Spiny Lobster. The gastrointestinal tract (GT) of Mud Spiny Lobsters obtained from the northern Bay of Bengal was examined for the presence of microplastics. Results demonstrated a significant amount of microplastic contamination in the samples, with an average of 4 particles per gram of the gastrointestinal system. For this study, we analysed 35 stomachs for Panulirus polyphagus and extracted and sorted 132 particles, an average of 3.15 ± 1.05 items/g GT, that resembled MPs for identification and characterisation by FTIR. Filament (65–72%), fiber (40–62%), and black (45–56%) were the most prevalent forms of MP across the different shapes, types, and colours. μ -FTIR measurements verified the presence of five different particle types (Polypropylene, Nylon-6, Ethylene Vinyl acetate, Polyethylene terephthalate, and Polyvinyl chloride), with Nylon-6 and Polypropylene constituting the majority of the compounds. The consumption pattern of microplastics by Mud Spiny Lobsters according to the length of their GT is also investigated. Further research is required to determine the origin of these sorts of plastics in the Bay of Bengal. Understanding this species' microplastic pollution can guide conservation and management efforts to safeguard marine life and livelihoods. These findings could be valuable for future monitoring efforts of MP contamination in seafood. 1Shahjalal University of Science and Technology, Sylhet 2023/08/10 (17:00-18:30)
Validating Remote Sensing Algorithms for Primary Productivity and Phytoplankton Functional Types in the Amazon River Plume 1Meredith Kime, 1Ajit Subramaniam Poster Session 1 The Amazon River Plume is a dynamic and nutrient-rich system which plays a significant role in coastal primary productivity (PP) and phytoplankton community structure. Supplying nearly 20% of global freshwater input to the world’s oceans, the content of the plume effects a large range, (Subramaniam, et al., 2008), especially with increases to anthropogenic nutrients (Wang, et al., 2019). Rapid advancements of remote sensing technology allow for water constituents to be assessed from space, post-hoc timeseries, and large-scale synoptic data acquisition not possible in remote locations otherwise. However, the Amazon River Plume is a complex system consisting of many different sources of matter, which may underestimate chlorophyll-a satellite measurements used for PP estimates and phytoplankton functional type differentiation. These estimates are closely related through their influence on nutrient cycling, and implication of biogeochemical processes. Using data from MODIS, MERIS, VIIRS, GCOM, and Sentinel 3a and 3b (OLCI), this study seeks to validate satellite-based PP and phytoplankton functional types compared to in-situ data collected over a series of previous cruises along the Amazon River outflow. Using VGPM, Eppley VGPM (Behrenfield & Falkowski, 1997) and CbPM (Westberry et al., 2008) algorithms for PP, and for assessing phytoplankton functional types from space (Sathyendrnath, et al., 2014), paired comparisons between in-situ measurements for both PP and phytoplankton functional types will be made to validate these valuable data resources. At this location, remote sensing measurements have yet to be validated with in-situ data, thus filling a critical knowledge gap in the wake of climate change. 1Columbia University, USA 2023/08/09 (17:30-19:00)
Schistosomiasis landscapes in the Middle Paranapanema Watershed, Sao Paulo, Brazil 1Milton Kampel, 1Vivian Silva, 1Rafael Anjos, 2Raquel Gardin Sanches Palasio, 1Isabel Escada, 3 Roseli Tuan, 1Antônio Migue, 1 Vieira Monteiro Poster Session 2 Schistosomiasis is one of the most important parasitic diseases in tropical regions. In Brazil, this disease is caused by infection with Schistosoma mansoni, whose intermediate hosts are the freshwater snails Biomphalaria glabrata, B. straminea and B. tenagophila. Human transmission occurs through contact with water infested with larval forms (cercariae) of S. mansoni. Precarious, inadequate, or non-existent basic sanitation conditions allow the contamination of water reservoirs and expose the populations that use these water bodies for leisure, agricultural, fishing, domestic and other activities, increasing the risk of transmission. This work aims to identify and characterize the potential landscapes of schistosomiasis infection according to levels of potential risk of exposure and contact between humans and intermediate hosts in the Middle Paranapanema watershed, Sao Paulo, Brazil. A typology was proposed for landscape patterns associated with the disease production. The study area was divided into a regular cellular space populated with remote sensing, geoenvironmental and socioeconomic data. Variables such as drainage, edges of water bodies and classes of land use, among others, were considered in the analysis. Classification techniques based on decision trees were used to produce a map that indicates potential areas to the infection of schistosomiasis where it is suitable for the existence of snails and contact between human and parasite. It is expected that the results obtained can serve as support for schistosomiasis surveillance and control actions, indicating the areas most prone to the resurgence of schistosomiasis. 1National Institute for Space Research (INPE), Brazil; 2University of Sao Paulo, Brazil; 3Pasteur Institute, Brazil 2023/08/10 (17:00-18:30)
The role of Biophysical Coupling in the distribution of Chlorophyll-a along the South West Coast of India 1Muhammad Shafeeque, 1Grinson George, 2Shubha Sathyendranath, 3Alungal N Balchand, 4Phiros Shah, 2Trevor Platt, 1Gopalakrishnan A Poster Session 1 The surface Chlorophyll-a (Chl-a) values of the south-west coast of India are highly dynamic, with seasonal and annual variations in response to different forcing mechanisms. A study has been conducted on long-term Chl-a variability and the possible causative factors that regulate its distributions in in this area. The wind-induced upwelling, mesoscale eddies, marine aerosols and precipitation were considered as factors responsible for Chl-a variability, utilising remotely sensed data for Chl-a, Sea Level Anomaly (SLA), Sea Surface Temperature (SST), Aerosols, Winds and Currents during the period 1998–2021. The results indicated a complex pattern of relationships in a region where many Essential Climate Variables (ECVs) co-vary with one another. The variability in Chl-a during the past decades in the study region was related to the prominent changes in the other marine ECVs considered, which are mainly controlled by basin-scale to mesoscale processes. The phase relationships between the variables revealed some underlying causes, even though it was challenging to interpret causal linkages from mere correlations. Wind-induced upwelling dominated over all other types of forcings in enhancing biological production (as indicated by high Chl-a values). Inter-annual and inter-seasonal variability of Chl-a concentration were observed from time-series analysis. The inter-annual variability of dominant ECVs revealed perturbations linked to extreme climatic events such as El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). The co-occurrences of such events have a significant impact on biological processes? and on the distribution of dependent variables?. 1ICAR- Central Marine Fisheries Research Institute, India; 2Plymouth Marine Laboratory, UK; 3Cochin University of Science and Technology, India; 4Kerala University of Fisheries and Ocean Studies, India 2023/08/09 (17:30-19:00)
Spatiotemporal variations around IORS using phytoplankton protein algorithm in the northern East China Sea 1Myeongseop Kim, 1Sang Heon Lee Poster Session 2 Among the macromolecular composition of phytoplankton, proteins (PRT) play an important role in biological processes, and have high energy transfer efficiency to higher trophic levels than other components (carbohydrates, lipids). However, field observations for PRT have limitations in identifying high-resolution spatio-temporal patterns, so long-term observations using ocean color satellites are required. In this study, a new regional algorithm was developed for the PRT concentration variation of phytoplankton at surface around Ieodo Ocean Research Station (IORS) in the East China Sea (ECS). Unlike the algorithm developed previously for the East/Japan Sea, an improved PRT algorithm for the ECS was derived using only chlorophyll-a (Chl-a) in this study, and the switching Chl-a algorithm based on turbidity condition used for the PRT algorithm was applied in this study using the satellite data provided by the Copernicus Marine Environment Monitoring Service (CMEMS). The revised PRT algorithm in this study improved the satellite-derived PRT estimates. Based on the new PRT algorithm, the monthly concentrations of satellite-derived PRT at IORS ranged from 38.2 μg L-1 to 132.6 μg L-1, with a mean value of 61.3 ± 21.4 μg L-1 from 2003 to 2021. Climatological seasonal mean of PRT concentration showed the highest value in spring (74.5 ± 23.2 μg L-1) and the lowest value in winter (57.2 ± 8.3 μg L-1). The new PRT algorithm developed for the ECS could contribute to long-term monitoring the PRT variability of phytoplankton responding to various environmental characteristics driven by various ocean currents and Changjiang Diluted Water. 1Pusan National University, South Korea 2023/08/10 (17:00-18:30)
Phytoplankton ecology in-relation to environmental variables in the coral ecosystem of Bangladesh 1Nabanita Das, 1Subrata Sarker Poster Session 2 Coastal ecosystem of Bangladesh is considered as the hotspot of species diversity and phytoplankton play a key role in maintaining these species diversity. However, very limited studies are available to understand the ecology of phytoplankton from this area. Thus, present study aimed to understand the seasonal ecology of phytoplankton in a coral reef ecosystem of Bangladesh. Data on environmental variables (i.e. temperature, salinity, dissolved oxygen (DO), chlorophyll, turbidity, nitrite, phosphate, silicate) were collected from 10 sampling stations during 2022 from the Saint Martin’s Island. This study found strong seasonality in environmental conditions from the coral reef ecosystem. However, no significant variation in vertical profiles of environmental variables was observed which suggested that the aquatic ecosystem around Saint Martins’ Island is well mixed. Water mass significantly varied during north-east monsoon than other seasons. Chaetoceros radican, Tripos trichoceros, Cylindrotheca Closterium, C. convulutus, Tripos muelleri, and Cyclotella striata species were found as dominant species. Planktoneilla sol and Ornithinocercus steinii occurred throughout the year but the abundance of these species was very low. Co-occurrence matrix showed that 189 pair of species can co-occur while 75 pairs occurred randomly. Generalized Additive Model found that 7 explanatory variables influence the abundance of phytoplankton species around the Saint Martins’ Island. Among them, Salinity, DO, nitrite and silicate concentration explained maximum variability in species abundance. This study reflects comprehensive assessment of the phytoplankton ecology around the Saint Martin’s Island. Thus, this study will play vital role to understand the food chain ecology of sub-tropical coral patches. 1Shahjalal University of Science and Technology, Bangladesh 2023/08/10 (17:00-18:30)
Oxygen Minimum Zone in the Bay of Bengal and its Characteristics 1Nadim Mahmud, 2Bradford S Barrett, 1Kh Dola Wahid 1Most Israt Jahan Mili Poster Session 1 Occurrence of intense oxygen minimum zone (OMZ) is known in the Bay of Bengal (BoB), but it has been recently reported to have become more acute and is at its tipping point. This project will show that the intensification of OMZ to acute condition is a random and short-term rather than perennial phenomenon based on re-evaluation of old and recent information in the BOB. Short-term modifications in dissolved oxygen (DO) in the OMZ are caused by balance among physical forces: salinity stratification, occurrence of cyclonic (CE) and anticyclonic eddies (ACE). The analysis will reveal that physical forces, particularly ACEs, do not allow it to become a dead zone. The oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about 200 to 1,500 m (660 to 4,920 ft), depending on local circumstances. Unlike its neighboring Arabian Sea, the Bay of Bengal OMZ is somewhat different in nature. It still shows a trace of oxygen at 70m depth and below, ranging from 032-. 064 mg/l, albeit way below the Oxygen level (5 mg/l) needed to support aquatic life and other uses. This study supports the idea that there is more oxygen variation in the upper 200 m of the water column and no deeper than that. This study further supports the idea that a decrease in oxygen concentration occurs between June and July when a A warm core eddy occupies the region. Whereas the offshore area had less oxygen, the Coastal water was more oxygenated. To comprehend the seasonal pattern, it is necessary to study the fluctuation in more detail in terms of general physical factors. 1Bangabandhu Sheikh Mujibur Rahman Maritime University, Bangladesh; 2Oceanography Department, U.S. Naval Academy (USA) 2023/08/09 (17:30-19:00)
Exploiting technological advances to develop resilience of coastal communities to extreme weather events 1Nandini Menon N, 1Ranith R, 1Rithin Raj M, 2 Grinson George, 3Anas Abdulaziz, 4Shubha Sathyendranath Oral Session 5: Water Quality and human health Climate-change-induced global warming, and shifts in precipitation and drought patterns, exacerbated by population pressure and poor sanitation conditions, are increasing the threats from diseases transmitted via water. Here we present the results of a study on the impacts of extreme weather events on the sanitation conditions of the coastal community of Kerala, in India. A survey on the sanitation aspects, availability of clean drinking water and incidence of water-borne diseases was done in six selected vulnerable coastal villages of Kerala. Based on analysis of the in-person survey data, seven questions were selected for was an application developed for use on mobile phones. The application, CLEANSE, will be made available to citizen scientists to collect information on sanitary conditions. Based on their responses, a vulnerability score will be calculated and provided to the citizen, displaying the health vulnerability status of their locality (red-high, blue-moderate and green-low), which can be updated in real time whenever there is any damage to sanitary infrastructure or in the event of flooding or other extreme events, so that remedial action for prevention of outbreaks of water-borne diseases could focus on locations that are most under threat. The application also contains three questions for self-validation and updates. This resource enhances the potential for developing cost-effective methods to build capacity to monitor risks to human health from water-borne diseases. 1Nansen Environmental Research Centre India; 2ICAR-Central Marine Fisheries Research Institute, Kochi, 682018, India; 3CSIR-National Institute of Oceanography, Kochi-18, India; 4Plymouth Marine Laboratory, Plymouth, Devon, UK 2023/08/10 (13:30-14:00)
Variability of Sea Surface Temperature related to Chlorophyll-a in Simeulue Island Coastal Waters, West Sumatra Sea 1Nazli Raudhati, 2Widodo Setiyo Pranowo, 3Edwarsyah Oral Session 1: Physical and biological interactions Simeulue Island, in Aceh Province, is one of the islands located in the Indian Ocean and separated by 150 km from the mainland of the island of Sumatra. Simeulue Island is rich in water and coastal resources. Temperature and chlorophyll-a are two parameters that affect the distribution of a fish species. Sea surface temperature variability affects the level of chlorophyll-a pollution in Simeulue Island waters. This study aims to analyze the daily temperature variability of the Simeulue island water surface. Sea surface temperature data downloaded from Hycom and chlorophyll-a distribution data downloaded from Erddap were then analyzed in space and time using the Ocean Data View (ODV) application. The maximum temperature of Simeulue waters in 2017 was relatively high in July, with a temperature value of 27.5–34°C and a chlorophyll-a distribution of 0.05–0.65 mg/m3. The minimum temperature of Simuelue waters in 2017 was relatively low in January, more precisely occurring in the western monsoon with a temperature value of 26–31°C and a chlorophyll-a distribution of 0–2.25 mg/m3. Temperature greatly affects the ban on chlorophyll-a. The increase in sea surface temperature in 2017 every month was only 1°C, while the increase in chlorophyll-a was 0.1 mg/m3. 1IPB University, Indonesia; 2Research Center for Climate and Atmosphere (PRIMA), National Agency of Research and Innovation (BRIN), Indonesia; 3Aquatic Resources Study program, Faculty of Fisheries and Marine Sciences, Teuku Umar University, Indonesia 2023/08/09 (12:00-12:15)
The Ocean as a Common Weal 1Nick Owens Opening Keynote Common weal, sometimes written as commonweal, is of archaic origin meaning “wealth shared in common” or “for the well-being of all”. More than ever society needs to recognise the ocean as a common weal: first that there is only one ocean but second the multiple, simultaneous uses society imposes upon the ocean. In this latter regard the ocean is being used for the provision of services, exploited rather than the sense of wealth and well-being – a gift. One hundred and fifty years ago HMS Challenger was at sea on her momentous, almost 70,000 nautical mile, expedition which transformed oceanography into the science we know today. It is surely time for another revolution in marine science through inspirational messaging. Trevor Platt was an inspirational messenger and the Foundation bearing his name has the ambition to inspire new generations on their voyage. In this talk I shall examine the notion of the ocean as a ‘common weal’, the current conflict of the ocean as a service rather than a gift and the need for effective messaging to reverse this position. 1Scottish Association for Marine Science, UK 2023/08/09 (09:20-10:05)
Time series analysis to evaluate the management efficacy of Indian MPAs 1Niya Joseph K, 1A Gopalakrishnan, 2Nandini Menon N, 2Ranith R, 1Grinson George Poster Session 2 The Marine Protected Areas (MPAs) in India are established for the conservation of biodiversity and the welfare of people who rely on it. Of considerable importance in India are the MPAs, that include coral reefs, which are sensitive to the insults of climate change. Despite the protected status, coral reefs of the Indian EEZ, particularly those of Lakshadweep, Gulf of Mannar, and Andaman and Nicobar islands, undergo significant bleaching and phase shifts. In this context, well-defined objectives and monitoring programmes to efficiently manage the MPAs are the need of the hour. The present study utilised the time series satellite data on SST, Chl-a, Salinity, and PAR from NOAA Coral Reef Watch, Ocean color, and APDRC and analysed their influence on Live Coral cover (LC), Dead Coral cover (DC), and Macro algal cover to understand the response of the ecosystem to changing climate. Analysis of such responses is crucial in identifying the system’s resilience and vulnerability to climate change and in identifying thresholds that can cause a shift in ecological state. Each response was regarded as a separate criterion, and MPAs were ranked accordingly using a Multi-criteria analysis model. The outcome can be helpful in developing adequate management strategies. 1ICAR-Central Marine Fisheries Research Institute (CMFRI), Kochi, India; 2Nansen Environmental Research Centre (India) 2023/08/10 (17:00-18:30)
Lesson Learnt From Padjadjaran Oceanographic Data Centre Portal 1Noir Primadona Purba, 1Ibnu Faizal, 1Ajeng Wulandari Poster Session 2 After two years launching, one of ocean portal database from Universitas Padjadjaran is evaluated. The purpose of PODC (Padjadjaran Oceanographic Data Center) was built to provide easy access to marine data which until now is still very expensive and difficult to obtain. For this reason, the purpose of PODC ( is a marine database that can be integrated with various marine instruments that are expected to be supported by agencies and universities in archipelagic countries. Currently PODC has been integrated with 3 oceanographic instruments and seawater quality measuring devices. Currently, more than 1500 data including the chemistry and physical parameters that are collected from in situ measurements. In the future, the portal will be integrated with other government institutional data to provide comprehensive information. Furthermore, collaboration from archipelagic countries should be conducted to gain more impact and provide robust datasets. 1Department of Marine Science, Faculty of Fishery and Marine Science, Universitas Padjadjaran 2023/08/10 (17:00-18:30)
Phytoplankton photosynthesis in oceanic oxygen-depleted waters 1,2Osvaldo Ulloa, 1Montserrat Aldunate, 3William K. W. Li, 3Venetia Stuart Poster Session 2 In all major oceanic oxygen minimum zone (OMZs) dim but sufficient light can be available for unique OMZ cyanobacteria lineages to thrive in the subsurface oxygen-depleted waters. The oxygen produced by these oxygenic phototrophs is immediately used by aerobic microorganisms, generating a cryptic oxygen cycle. While information about the phylogenetic diversity and genomic characteristics of OMZ cyanobacteria has recently become available, unraveling their ecophysiology has been challenging, mainly because they remain uncultivated. In this symposium, we will present field observations of the Photosynthesis versus Irradiance (P-E) relationship under controlled oxygen conditions, light absorption characteristics, cell abundance and distribution, and pigment composition obtained for natural populations of OMZ cyanobacteria in the eastern tropical Pacific. Altogether, results show a photosynthetically active cyanobacteria community well adapted to oxygen deficiency and low light conditions in the OMZ, the latter due principally to its observed high light absorption characteristics resulting from very high intracellular concentrations of divinyl chlorophyll-a and –b. Incorporating this new information into models of phytoplankton distribution and primary production will allow —for example— to evaluate the impact of increasing ocean deoxygenation due to climate change on marine primary production and biogeochemical cycling in expanding OMZ regions. 1Instituto Milenio de Oceanografía, Concepción, Chile; 2Universidad de Concepción, Chile; 3Bedford Institute of Oceanography, Canada 2023/08/10 (17:00-18:30)
Levels of Polycyclic Aromatic Hydrocarbons and Heavy Metals in marine bird eggs from two national parks in Senegal 1Ousmane Diankha, 1Ibrahima Gueyeh Poster Session 2 The present study was conducted to investigate the quality of four marine bird eggs in two national parks in Senegal in order to determine the quality of these ecosystems before oil exploitation in Senegal. The eggs were collected from the breeding grounds of these species in two National Parks (Parc national du Delta du Saloum in the Petite Côte and Parc National de la Langue de Barbarie in the nouthern in the Grande Côte). The heavy metals (Pb, Cd and Hg) was estimated with the help of absorption atomic spectrometry, while HAP were detected using GC-MS by following open acid digestion technique. This present work, the first in Senegal, shows that the eggs of royal tern, Caspian tern, slender-billed gull and grey-headed gull, are contaminated by PAHs and metals. The royal tern eggs sampled at the PNLB and those of the grey-headed gull sampled at the PNDS contain the highest levels of PAHs. Benzo(a)pyrene, one of the most toxic PAHs, is the compound most present in the contents of the eggs of the species examined, except the Caspian tern. Benzo(a)pyrene concentrations in royal tern and grey-headed gull egg contents are above the median lethal concentration. Lead is the heavy metal with the highest concentration in the eggs of the species studied. Mercury, despite its high effect, is very low in the contents of the eggs of the species concerned by this work. 1Université de Thiès is located in Thiès, Senegal 2023/08/10 (17:00-18:30)
Effect of temperature and light intensity on the growth and physiology of Prorocentrum lima: A red tide forming toxic dinoflagellate 1Oyeshina Oyeku, 2Subir Mandal Poster Session 2 The current study sought to examine the potential role of water temperature and water column irradiance in recent proliferation of Prorocentrum species (e.g., P. lima) into large biomass blooms along the Indian peninsula coast. A strain of Prorocentrum was isolated from the Bay of Bengal coast of India. The identity of its clonal culture was established using light and scanning electron microscopy and molecular phylogenetic analysis of the LSU rRNA sequence. The effect of temperature (20, 25, 30, 35oC) and light intensity (LL = 50 ± 5 and HL = 150 ± 5 µmol photons m-2 s-1) on its growth (µ), maximum cell density (MCD), and cellular diarrheic shellfish toxin (DST), lipid peroxidation (LPX) and superoxide dismutase (SOD) levels was evaluated using established protocols. Significant differences between treatments were evaluated using student’s T-Test and ANOVA tests. The Morphological features observed (e.g., large central pyrenoid with starch sheath) and the LSU rDNA phylogeny confirmed the isolate as P. lima. Its µ and MCD increased with increasing temperature up to 30oC but decreased with increasing light intensity at p < 0.05. Maximum growth (µ = 0.173 ± 0.000 div. day-1 and MCD = 49,500 ± 200 cells mL-1) was recorded in the 30oC-LL condition, while the least (µ = 0.065 ± 0.003 div. day-1; MCD = 6,200 ± 0 cells mL-1) was recorded in the 20oC-HL condition. Cellular DSPT, SOD and LPX levels were lower under optimal (30oC-LL) growth condition at p<0.05. High temperature and low irradiance favor the proliferation of P. lima. 1Pure and Applied Biology Programme, Bowen University, P. M. B 284, Iwo, Osun State, Nigeria; 2Division of Applied Phycology and Biotechnology, CSIR-Central Salt & Marine Chemicals Research Institute, Gijubhai Badheka Marg, Bhavnagar-364002, Gujarat, India 2023/08/10 (17:00-18:30)
Does the ocean contribute to seasonality in atmospheric CO2? 1Peter Land, 1Shubha Sathyendranath, 1Thomas Jackson Poster Session 2 It is often assumed, based on simple scale analysis, that a perturbation to in-water CO2 concentration (such as a reduction in oceanic CO2 in surface waters due to a phytoplankton bloom) will decay only very slowly through air-sea CO2 exchange, with a typical time constant of up to one year for a mixed-layer depth of 100 m. This leads to the conclusion that the seasonality in atmospheric CO2 is driven largely by seasonality in terrestrial biological processes, rather than by marine biological processes. We present the results of calculations using global estimates of mixed-layer depth, dissolved inorganic carbon, CO2 concentration, Revelle factor and CO2 transfer velocity, all of which vary spatially and temporally, to calculate the time constant of air-sea exchange of CO2 globally. In this work we make use of existing datasets to calculate this time constant globally at one-degree monthly resolution to see whether there are times and regions where exchange happens on a short enough timescale for oceans to contribute to atmospheric CO2 seasonality. We can then examine these cases at higher spatiotemporal resolution and estimate the impact of phytoplankton blooms on atmospheric CO2 drawdown. We find a typical transfer time of about 120 days with strong spatiotemporal heterogeneity. Rapid transfer occurs all year in the Baltic Sea, and seasonally in several Arctic and North Pacific regions, the Northwest Atlantic, and patches off the tip of South America and New Zealand. Transfer is generally faster at mid to high latitudes. 1Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK 2023/08/10 (17:00-18:30)
Optical properties of a shallow coral reef environment in French Polynesia 1Pirta Palola, 2Varunan Theenathayalan, 2Victor Martinez-Vicente, 3Antoine Collin, 1Rosalie Wright, 1Melissa Ward, 4Claudia Giardino, 4Monica Pinardi, 5Patricia Lopez Garcia, 1Lisa Wedding Oral Session 2: Marine Optics & Ocean Colour The lack of spatial data at high spatial-temporal resolutions is hindering the development of more efficient coral reef management strategies in many regions of the world. Encouragingly, recent advancements in remote-sensing technologies offer an unprecedented opportunity to map and monitor coral reef environments over large spatial scales and at high spatial-temporal resolutions. However, in shallow coral reef ecosystems, accurately understanding the optical properties of both the water column and the benthos is a key condition for the development of advanced remote sensing applications. Yet, few studies have described optical properties of very shallow reefs (<2m deep), undermining the accuracy of remote-sensing applications in these environments. In this study, we address this knowledge gap and provide a detailed description of the optical characteristics of a very shallow coral reef environment at Teti’aroa, a low-lying atoll in French Polynesia. During a field campaign in July-August 2022, we measured benthic reflectance and above-surface remote-sensing reflectance at 21 sites using TriOS RAMSES hyperspectral sensors with an optical resolution of 3.3 nm. At each site, we also collected water samples for subsequent lab analyses of inherent optical properties. The results indicate strong benthic reflectance and distinct spectral signatures of different coral types. Phytoplankton, non-algal particulate matter, and coloured dissolved organic matter all make non-negligible contributions to water column reflectance. The next step of this research project is to link these in-situ data with multispectral satellite and drone imagery acquired during the field survey. These findings will support the development of future coral reef remote-sensing applications. 1University of Oxford, UK; 2Plymouth Marine Laboratory, UK; 3Ecole Pratique des Hautes Etudes Paris Sciences Lettres, Benoît Stoll, Université de la Polynésie française, France; 4Italian National Research Council, Italy; 5National Oceanography Centre, France 2023/08/09 (14:00-14:15)
Phytoplankton size decrease in a warming Arctic: satellite and in-situ observations 1Priscila Kienteca Lange, 2Jens M Nielsen, 2Lisa B Eisner, 3Michael W Lomas, 2Calvin W Mordy, 2Jeanette Gann, 2Sage Osborne, 4Dale Robinson, 2Phyllis Stabeno Poster Session 2 Understanding the temporal and spatial variability of phytoplankton size is key to diagnosing potential trophic changes driven by climate change in the Arctic ecosystem. Large cells and cell agglomerates sink supporting benthic life, whereas smaller cells fuel planktonic and neritic production. Here, we compare empirical models (regional fits of Brewin et al. 2011, Hirata et al. 2011, GAM and Random Forest) using total chlorophyll concentrations and sea surface temperature (SST) as predictors for three phytoplankton size-fractions - picoplankton (<5 μm), nanoplankton (5-20 μm), and microplankton (>20 μm) - in the Bering and Chukchi seas. Regional parametrizations were developed using 266 in-situ surface chlorophyll measurements from 2017 and 2019, and temporal trends were compared to 1425 in-situ observations from 2003 to 2019. Then, the best regional model was chosen to assess variations in phytoplankton size over the period between 1988 to 2022 (Globcolor chlorophyll product). The comparison between global and regional Brewin models showed that the picoplankton fraction is greater in the Bering/Chukchi Seas than the global average. While the Random Forest model was the best for predicting picoplankton, the GAM performed best for predicting nano- and microphytoplankton. In the last 34 years, highest picoplankton chlorophyll contributions were observed in the warmest years (2017 to 2019), which coincides with in-situ observations and satellite estimates of the picocyanobacterium Synechococcus in the area. These results indicate that the recent increase in surface chlorophyll concentrations is due to the preferential increase in smaller phytoplankton, which may drive drastic changes in the Arctic food web. 1Universidade Federal do Rio de Janeiro, Brazil; 2National Oceanic and Atmospheric Administration, US; 3Bigelow Laboratory for Ocean Sciences, US; 4University of California, Santa Cruz, US 2023/08/10 (17:00-18:30)
Mesodinium blooms driven by marine upwelling and atmospheric heatwaves in Rio de Janeiro, Brazil 1Priscila Kienteca Lange, 1Mauro Cirano, 1Renata Libonati, 2Domenica T. Lima, 2Gleyci A Moser, 1Silvia Nascimento, 1Djacinto M Santos, 1Luiz Felipe M S Sousa, 1Lino Sander de Carvalho Poster Session 1 Mesodinium is a kleptoplastic protozoan that feeds on Cryptophytes and blooms in a wide range of estuarine and coastal marine environments. Mesodinium blooms are usually driven by water column stratification caused by heavy rainfall, freshwater run-off, or surface heating of the water column induced by marine and atmospheric heatwaves. At the coastal ocean of Rio de Janeiro, Mesodinium blooms recently became frequent, as heatwaves became recurrent in Spring and Summer. Here, we investigate the possible atmospheric and oceanographic causes of Mesodinium blooms at the coastal ocean of Rio de Janeiro based on satellite ocean colour and sea surface temperature observations, in combination with in-situ meteorological (Met-Rio) and oceanographic (SiMCosta) data. These blooms can be easily observed due to their bright red colour since Mesodinium cells are motile and agglomerate at the first few centimeters of the water column. Therefore, we used a multiple band-ratio model (blue, green, red and red edge bands) to detect Mesodinium patches in Sentinel-3 OLCI (2017-2022) and S-NPP VIIRS (2012-2022) remote sensing reflectances. Mesodinium patches were largest and most frequent in Spring and Summer, when atmospheric heatwaves occurred in combination with low ocean temperatures due to the high intensity of the Cabo Frio upwelling system, being commonly associated to diatom and dinoflagellate blooms. Considering the impacts of Mesodinium blooms in the marine environment such as subsurface hypoxia, future projections of an increase in heatwave frequency in Rio can possibly disrupt the marine food web, directly influencing citizens that utilize the marine environment for tourism and fishing. 1 Universidade Federal do Rio de Janeiro, Brazil; 2 Universidade do Estado do Rio de Janeiro, Brazil 2023/08/09 (17:30-19:00)
Citizens as sentinels of Harmful Algal Blooms in Rio de Janeiro, Brazil 1Priscila Kienteca Lange, 2Ramayana Cavalcante, 1Renata Libonati, 3Domenica T. Lima, 3Gleyci A. Moser, 1Silvia Nascimento, 1Djacinto M. Santos, 1Lino Sander de Carvalho, 2Márcio S. Silva Poster Session 2 Harmful algal blooms (HABs) are recurrent at Rio de Janeiro’s coastline, driven by interaction of coastal waters by the upwelling system of Cabo Frio and eutrophic inland and estuarine waters, which fertilize coastal waters. Despite their high frequency, blooming phytoplankton species are undersampled and not well-described, and the specific interactions between nutrient sources and meteorological and oceanographic conditions are still unknown. As a consequence, the effects of these blooms on public health and coastal ecosystems are still unpredictable. To increase public awareness about HABs and bloom diagnostic efforts, this outreach project instructs and instigates beach and lagoon users (local population and tourists) using a combination of short lectures, water sports (surf and stand-up paddle boards, Polynesian canoes) for sampling, and foldscopes for the observation of the marine microscopic life. Foldscopes were used to determine which phytoplankton species is most representative, and its presence was associated to the water color. In January and February, foldscopes were distributed to collaborators and used to diagnose a major Tetraselmis bloom that is still happening along the coasts of Rio de Janeiro and São Paulo. After confirmation using powerful microscopes, images and information were posted in social media by the profiles of our participant laboratories, with high public engagement. In the next months, the outreach activity will be conducted on February 25th, 2023, as part of the INMar festival in collaboration with Rio’s City Hall, and other activities are planned for March and April. Activity photos and peoples’ impressions will be exposed in this poster. 1Universidade Federal do Rio de Janeiro, Brazil; 2Instituto Núcleo Maré, Brazil; 3Universidade do Estado do Rio de Janeiro, Brazil 2023/08/10 (17:00-18:30)
Assessing the Use of Mid-Resolution Satellites for Ecosystem Monitoring in the Chesapeake Bay, US 1,2Rachel Lazzaro, 1Paul DiGiacomo, 1,3SeungHyun Son, 4Nicole Bartlett Poster Session 2 In the Chesapeake Bay, the Eastern oyster is foundational in its provision ecosystem services from filter-feeding activities. Likewise, submerged aquatic vegetation (SAV) beds are important in reducing runoff impacts and shoreline erosion. However, SAV beds have undergone significant decline since the 1950s, and Eastern oyster populations have been overfished; as such, restoration and management efforts for these groups must consider changes in water quality, including sea surface temperature, turbidity, and chlorophyll-a, which can be derived from satellite imagery. Virginia's Middle Peninsula was selected as a target region for its classification as one of NOAA's Habitat Focus Areas, where oyster restoration and shoreline erosion reduction projects are underway. The region requires finer-scale spatial resolution due to smaller scale tributaries such as the York and Piankatank rivers. As such, a time series and seasonal analysis was generated using the Landsat Collection 2 Surface Temperature products from the Landsat 5 TM, Landsat 7 ETM+, Landsat 8 TIRS, and Landsat 9 TIRS sensors. A comparison with SST derived from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) was developed against the Landsat-derived surface temperature product to compare with trends derived from the higher temporal resolution product. Turbidity and chlorophyll-a concentration serve as indicators for water quality, and Landsat 8 OLI and Sentinel 2-A/B MSI were used to determine seasonal patterns in turbidity and chlorophyll-a. The resulting analysis is relevant in ecosystem monitoring and aquaculture management discussions for both SAV and oyster beds in the Chesapeake Bay. 1NOAA/NESDIS Center for Satellite Applications and Research (STAR), College Park, MD, USA; 2USA Global Science & Technology, Greenbelt, MD, USA; 3CIRA, Colorado State University, Fort Collins, CO, USA; 4NOAA/NMFS, Woods Hole, MA, USA 2023/08/10 (17:00-18:30)
Early Warning Of Harmful Algal Blooms In Northern Indian Ocean Using Machine Learning Methods 1Ranith Rajamohanan Pillai, 1Nandini Menon N, 2Varunan Theenathayalan, 2Peter I Miller, 3Lasse H Pettersson, 2Shubha Sathyendranathy Poster Session 1 Harmful Algal Blooms (HABs) have become a regular feature affecting the aquatic ecosystem health of the Northern Indian Ocean (NIO). In this study, we compared the performance of machine learning (ML) models such as artificial neural networks (ANN), extreme-gradient boosting (XGBoost) and support vector machines (SVM), when used to predict HAB events. Two ML-models were developed: one to predict the HAB associated Chl-a concentration (ML1-regression) and the other to predict the occurrence of HAB events (ML2-classification). Training data (dependent-variables) were obtained from our historic HAB-database for NIO. Chl-a concentration and presence/absence data of HAB from the database were used as dependent variables in ML1 and ML2 respectively. Remote sensing predictors used were Secchi disk depth, diffuse attenuation coefficient Kd(490), particulate backscattering coefficient and sea-surface temperature (SST). Water-quality predictors were taken from the CMEMS-biogeochemical reanalysis model. Multiple ML2-models were used with time-lagged interaction to check predictive skill using data from 1, 2, 3, 5 and 10consecutive days before the HAB incidence. The ML models were validated by simulating an actual Noctilucascintillans bloom event from the south-west Arabian Sea during December 2021. ML1-model simulations revealed that XGboost were best suited to predicting Chl-a concentration (r2=0.85/RMSE=1.07) during a HAB event. ML2-model simulations revealed that the 3-consecutive day SVM model outperformed other models (Kappa=0.8/balanced accuracy=0.8) in successfully simulating the 2021 HAB event. Although the 3-day SVM (ML2) and the XGBoost (ML1) could significantly simulate a Noctilucascintillans bloom event, fine tuning is required with ensemble ML-models to improve the prediction and early warning accuracy. 1Nansen Environmental Research Centre (India); 2Plymouth Marine Laboratory, UK; 3Nansen Environmental and Remote Sensing Center, Norway 2023/08/09 (17:30-19:00)
Pelagic respiration and biomass size spectra in the Humboldt Current System 1,2Renato Quinones, 2Rodrigo Montes, 1Rodrigo Gonzalez Oral Session 6: Size and ecosystem structure of aquatic communities Respiration is a critical biogeochemical process in nature. However, there are very few studies on the size-distribution of respiration at the community level of organization. Here, we analyze the size-distribution of biomass and respiration in the pelagic ecosystem off central-south Chile. Two cruises (spring 1998, winter 1999) were conducted (36° to 38°S) from the coast to 200nm offshore. Biomass was determined as ATP and potential respiration was estimated using the electron transport system activity. Each spectrum had 12 size-classes (from 0.7 to 8000 um). The size-distribution of biomass and respiration in both cruises can be described by linear normalized biomass (NBSS) and respiration (NRSS) size-spectra, constructed using ordinary least-squares regressions with log2 binning (OLSR). The slope of the NBSS ranged from -0.97 to -1.25 during the spring and from -0.86 to -1.56 during the winter, indicating wide variability in the distribution of biomass by size in both seasons. The slopes of the NRSS ranged from -1.19 to -1.64 and from -1.39 to -1.79 during spring and winter, respectively. Marked domes were also observed in NBSS and NRSS. In addition, the spectra were analyzed using a maximum likelihood estimation method that explicitly accounts for bin structure (bmle). The bmle slopes showed much lower variability between stations in comparison to the slopes based on OLSR. A comparison was done with NRSS obtained under pre-El Niño and El Niño conditions off northern Chile (23°S). Our results support the hypothesis that the distribution of respiration by size is a conservative property of pelagic ecosystems. 1Department of Oceanography, University of Concepcion, Concepcion, Chile; 2Interdisciplinary Center for Aquaculture Research (INCAR), University of Concepcion, Concepcion, Chile 2023/08/11 (10:15-10:30)
Inter-seasonal and inter-annual changes in the zooplankton community structure in a coastal station from Patagonia, Argentina (2018–2023) 1Rodrigo Daniel Hernández-Moresino, 1Antonella De Cian, 1Lucía Epherra, 2Antonela Martelli, 1Augusto C Crespi-Abril, 1Juan Pablo Pisoni, 1Elena S Barbieri, 1Brisa Halter Poster Session 2 Environmental conditions around the world ocean are drastically changing in response to greenhouse gases from anthropogenic activities. Continue time-series measurements at fixed locations are necessary to monitor ocean trends. The Nuevo Gulf Oceanographic Station (GNEO, 42°45'43.99"S - 65°1'29.97"W) is a coastal monitoring effort in Patagonia, Argentina, measuring the temporal variability of physical, chemical, and biological variables in these waters and supplying data to the NANO-DOAP project (A global study of coastal Deoxygenation, Ocean Acidification and Productivity) since 2021. At this time, we will present trends in mesozooplankton community structure from 2018 to the present. Vertical trawls were performed monthly, with a Hensen net from the dock of Puerto Madryn City. Taxonomic identification and quantification were conducted by semi-automatic analysis of digital images with ZooImage software. Changes in the community structure reflect changes in taxonomic composition among seasons, but no differences were evidenced among years up to date. There is an increase in the abundance from autumn to summer. Slopes of the size structure are similar from autumn to spring, where small copepods dominate with 60%. In summer, the abundance duplicates, increasing the proportion of small copepods to 70%, stepping the slope of the size spectra from -3 to -4 compared with the rest of the seasons. Small copepods dominated all seasons, followed by large copepods and appendicularians, the last ones mainly during the cold seasons. These surveys of zooplankton communities using semi-automatic tools are an effective and low-labour effort way of assessing the health status of urban coastal marine ecosystems. 1Centro Para el Estudio de Sistemas Marinos (CESIMAR)-CONICET, Argentina; 2National Institute for Fisheries Research and Development, Argentina 2023/08/10 (17:00-18:30)
Mitigating low signal-to-noise ratio in geostationary satellite ocean colour observation 1Ruth Mahubessy, 2Stéphane, 3Ewa Kwiatkwoska, 2Thibault Poster Session 1 The estimation of ocean color is one of the techniques in remote sensing used for the monitoring of environmental conditions such as phytoplankton, harmful algae or suspended particulate matter (SPM). This measurement is characterized by the water-leaving reflectance (WLR) which is the backscattering reflectance from the ocean received at top of the atmosphere. However, the WLR signal received at the sensor can be very small. One approach to improve the quality of the measured WLR is to study the signal-to-noise ratio (SNR) in the observed channel since SNR describes the proportion of the measured signal to the unwanted noise. This study aims to investigate the capability of a geostationary satellite, Himawari-8, in the ocean color observation by exploring the variation of the signal-to-noise ratio (SNR) in several areas. Noise evaluation has been performed over 8 geolocated grid-boxes with a spatial average of 5x5 pixels and a temporal average of 50 minutes. This work has been done by taking into account the grid-box distance to the Nadir and the local solar time variation. The results show that the SNR is affected by the position of the box relative to the coast and the local solar time. Overall, Himawari-8 seems to be capable of observing ocean color, especially with a satisfying temporal resolution, although the SNR is still far from the International Ocean Color Coordination Group (IOCCG) recommendations. Results are expecting to improve with the Flexible Combined Imager, the imaging sensor on board Meteosat Third Generation, which is set to be launch at the end of the 2022 and is equipped with a dedicated ocean color channel. 1Indonesian Agency for Meteorology Climatology and Geophysics, Indonesia; 2Météo, France; 3EUMETSAT, Germany 2023/08/09 (17:30-19:00)
XGBoost and TRIX models used in combination to assess and diagnose the trophic state of Coastal Wetlands: Ichkeul Lake 1Sabrine Sahbani, 1Béchir Béjaoui, 3Ennio Ottaviani, 4Eva Riccomagno, 3Enrico Prampolini, 5Sihem Benabdallah, 2Hechmi Missaoui Poster Session 2 In northern Tunisia, near the shore of the Mediterranean Sea, Ichkeul Lake is among the most productive ecosystems. However, this wetland is an example of an impacted lake due to the effect of climate change and the expansion of human activities. Therefore, the main objective of the present study is to characterize the trophic status of the Lake. A collection of historical data complemented by a sampling campaign was conducted to obtain a dataset consisting by 100 sampling observations of 13 environmental parameters for the period 2010_2020. Multimetric trophic index TRIX was used to provide the degree of trophic status of the lake. While XGBoost model was used to build a predictive model of chlorophyll-a and it was evaluated by the coefficient of determination R2. Moreover, the link between chlorophyll-a and input variables was also studied using Pearson correlation. The observed TRIX values inside the lake show a non-uniform distribution and a variation between seasons. While the results of XGBoost model show that the most important predictor of chlorophyll a variation appears to be dissolved oxygen, followed by nitrate and temperature, which is consistent with the Pearson correlation results. In the broader context of the coastal wetlands’ studies, the study of coastal lagoons and other transitional ecosystems, this approach, which combines TRIX and XGBoost models, could be used to predict the evolution of the trophic status of these environments. It can be used in decision making by civil authorities, economists, as well as other interested stakeholders. 1National Institute of Marine Sciences and Technologies, Tunisia; 2National Institute of Agronomy of Tunisia; 3OnAIR srl, Italy; 4University of Genova, Italy; 5Center for Water Research and Technology, Tunisia 2023/08/10 (17:00-18:30)
Machine Learning techniques for forecasting the effect of Climate Change and Anthropogenic pressures on Coastal wetlands (Ichkeul Lake, Ramsar Site) 1,2Sabrine Sahbani, 1Béchir Béjaouin, 3Ennio Ottaviani, 3Enrico Prampolini, 4Sihem Benabdallah, 4Hechmi Missaoui Oral Session 6: Size and ecosystem structure of aquatic communities The effect of environmental conditions on the European eel species during its non-migratory growth phase is seldom studied in Mediterranean areas. Ichkeul wetland is one of the important habitats for the eel population. Nevertheless, this habitat is jeopardized by human settlement and Climate Change, which have a negative impact on the eel stock. Accordingly, the aim of this study is to assess the effect of environmental factors on the eel stock, and thus to gain insight into the state of the lake, as the eel is an excellent bioindicator of the state of ecosystems. Random Forest and Cubist models were developed for this purpose using a dataset from long-term (2010-2020) environmental and biological monitoring of Ichkeul Lake. Validation and comparison of the models have been performed using the coefficient of determination (R2). A sensitivity analysis was also performed to judge the predictors’ importance. The results revealed pronounced seasonal variability of the environmental parameters. While the models’ outcomes highlighted their best predictive performance and revealed that the most important predictors of eel landing appear to be water level, salinity, and turbidity. These results are consistent with the relationships found with Pearson correlation. Our results proved that these variables should always be included in management measures and can be widely extended to other Tunisian coastal ecosystems. The study has also proven that the sustainable approach, which combines the two models, can be used in decision making by civil authorities and other interested stakeholders. Keywords: Anguilla anguilla; Ichkeul Lake; Anthropogenic pressures; Climate Change; Machine Learning; Cross-validation. 1National Institute of Marine Sciences and Technologies, Tunisia; 2National Institute of Agronomy of Tunisia; 3OnAIR srl, Italy; Eva Riccomagno, University of Genova, Italy; 4Center for Water Research and Technology, Tunisia 2023/08/11 (09:45-10:00)
Annual cycle of water quality in the Cochin estuary, southwest coast of India 1Safin I P, 1Vijith V Poster Session 2 Cochin estuary has the shape of a lake, with rivers discharging fresh water at several locations and two narrow openings to the sea. As this region comes under the influence of monsoon climate, river discharge to the estuaries is highly seasonal. Hence, the estuary's salinity field is never steady, changing from salt wedge to well mixed over the year; these estuaries are often referred to as monsoonal estuaries. The city of Cochin, located around the estuarine system is witnessing rapid urbanization and a growing population. Therefore, maintaining the health of the estuary is very crucial for its sustenance. Many issues affect the health of the Cochin backwaters, among which the growth of water hyacinths is a severe problem to address. They are freshwater-growing invasive species of aquatic weed reaching the estuary when a saltwater barrage is opened. As they can't survive in the saline water, it starts decaying, making the water anoxic and thus causing severe water quality issues. Moreover, they act as a thick layer over the water blocking the sunlight from penetrating. This condition is to be monitored as it is hazardous to the aquatic ecosystem. In this study, we discuss the year-long temperature, salinity, and dissolved oxygen variability seen in the continuous measurements from the data buoy system deployed by the Department of Physical Oceanography, CUSAT. We also propose to monitor the distribution of water hyacinths in the Cochin estuarine system using satellite multispectral images and investigate its dependence on the estuary's salinity. 1Cochin University of Science and Technology, Kochi, India 2023/08/10 (17:00-18:30)
Driver Of Phytoplankton Community Dynamics In Tropical Coastal Habitats 1Samiul Huda, 1Subrata Sarker, 1Tania Sultana Oral Session 4: Physiological ecology of marine phytoplankton Investigation of phytoplankton dynamics of the coastal habitats is important to understand the trophodynamics of the aquatic ecosystem. However, coastal habitats of the tropical region are fewer studies. Thus, this study aims to understand the community structure and drivers of phytoplankton in tropical coastal habitats. We collected the data on phytoplankton, zooplankton, and environmental conditions from the estuarine, mangrove, and coral reef ecosystems of Bangladesh which are examples of the least studied tropical aquatic habitats. Samples were collected during the dry season from 2020 to 2021. Our study found that estuarine, mangrove, and coral reef ecosystem varies from each other in terms of eco-hydrological characteristics. We also found that diatom is the dominant phytoplankton group in all types of habitats. However, dominant species vary along the habitat types. Species of the genus Coscinodiscus were found dominant in estuaries while species of genes Ceratium and Chaetoceros were dominant in the coral reef system. In the mangrove ecosystem, both Coscinodiscus and Chaetoceros were found dominant. The concentration of micronutrients (i.e., silicate, nitrate, and phosphate) was found as the major driver in all habitat types. We also found that zooplankton plays a vital role in shaping the phytoplankton community structure in the coral reef ecosystem. Our study concludes that phytoplankton dynamics in the coastal habitats of the tropical area are mainly driven by nutrients that are lined with riverine inputs. 1Shahjalal University of Science and Technology, Bangladesh 2023/08/10 (12:15-12:30)
Long-term variability of phytoplankton size classes in relation to total algal biomass and bloom in the northern Arabian Sea 1Sanjiba Kumar Baliarsingh, 1Aneesh A Lotliker, 1Alakes Samanta, 2Shreeharsha M Hegde Poster Session 1 The present study analyses the long-term pattern of chlorophyll-a (Chl-a) concentration of phytoplankton size classes (pico, nano, and micro) in the Northern Arabian Sea (NAS). The abundance-based models by Brewin et al. (2010) and Sahay et al. (2017) were used to retrieve PSC from Moderate Resolution Imaging Spectroradiometer onboard Aqua satellite (MODISA) data. The validation of satellite-estimated PSC, with the in-situ data from FORV Sagar Sampada expedition (SS348, SS356, and SS383), signified better efficacy of the Sahay et al. (2017) algorithm. The monthly climatological variability of total Chl-a concentration in the NAS (14 to 22° N and 60 to 68°E) revealed a similar temporal pattern with a gradual increase from November to February and a subsequent gradual decline till April. Specifically, a significant Chl-a upsurge from January to February-March was attributed to phytoplankton bloom with the demarcation within parallels of 20 to 24° N and 62 to 66°E as the core bloom area. The PSC monthly climatology revealed micro-phytoplankton following the total Chl-a, with increment during the north-east monsoon (NEM) period when NAS experiences bloom of diatom followed by dinoflagellate (Noctiluca scintillans). Pico-phytoplankton concentration revealed an inverse relation with micro-phytoplankton in the NAS over the months. As the effect of NEM reduced, nano-phytoplankton flourished with relatively higher concentration and distributed uniformly in the NAS during the inter-monsoon period. 1 Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Government of India, Hyderabad-500090, India; 2 Department of Marine Geology, Mangalore University, Mangalagangotri– 574199, India 2023/08/09 (17:30-19:00)
Testing a hyperspectral, bio-optical approach for identification of phytoplankton groups in the Chesapeake Bay estuary 1S Morgaine McKibben, 1Stephanie Schollaert Uz, 1Sherry L Palacios Poster Session 1 Satellite-based identification of phytoplankton groups is among the new capabilities anticipated from next-generation hyperspectral ocean color sensors. In this work the bio-optical Phytoplankton Detection with Optics (PHYDOTax) approach for deriving taxonomic class-level phytoplankton community composition (PCC, e.g. diatoms, dinoflagellates) from hyperspectral information is evaluated in the Chesapeake Bay estuary on the U.S. East Coast. PHYDOTax deconvolves the spectral shape of remote sensing reflectance (Rrs) into component PCC groups using a library of spectral signatures representing optically active components anticipated in the water being observed. PHYDOTax is among relatively few regionally customizable, optical PCC differentiation approaches available for optically complex waters, but the approach has not been tested beyond the California coastal regime where it was initially developed. Study goals include: 1) regional parameterization, including novel addition of colored dissolved organic matter (CDOM) and non algal particles (NAP) to the algorithm, and 2) performance assessment using field-based Rrs and pigment data from two cruise campaigns. Testing was conducted at hyperspectral-relevant spectral resolutions (1nm, 5nm, 10nm) with and without incorporation of CDOM and NAP. Statistical performance was typically robust for cryptophyte and cyanophyte phytoplankton groups with variable to poor results for dinoflagellate and diatom groups. Small, but significant, differences were observed in algorithm output at varied spectral resolutions, but no significant differences were observed in runs with or without CDOM and NAP. Based on these datasets, PHYDOTax can differentiate some phytoplankton groups in an estuary. The approach warrants further investigation with in estuaries and other optically complex regimes. 1NASA Goddard Space Flight Center/NASA Postdoctoral Program, USA 2023/08/09 (17:30-19:00)
A study on the bio-optical characteristics of the coastal waters off Kochi and Chennai 1Sara Xavier, 2Anju R, 1Nandini Menon N, 1Ranith Rajamohanan Pillai, 3Anas Abdulaziz, 4Shubha Sathyendranath, 5Marie-Fanny Racault, 5Grinson George Poster Session 1 The in-situ bio-optical properties of the coastal waters off Chennai (east coast) and Kochi (west coast), India were examined during three seasons during 2019-2022. The bio-optical properties studied were: chlorophyll concentration, absorption coefficients of particulate matter, detrital matter, phytoplankton and coloured dissolved organic matter, along with phytoplankton taxonomy and numerical abundance. The results showed some similarities in the bio-optical properties of the two study sites, irrespective of the differences in seasons. For example, detrital matter was the major contributor to the absorption budget in both coasts. Also, diatoms were the dominant phytoplankton in both the coasts throughout the study period. But the variability of chlorophyll off Kochi was higher, ranging from 0.45 to 16.5µg/l, compared with that off Chennai (0.23 to 6.5 µg/l). Off Kochi, the highest phytoplankton density was observed during the monsoon season, whereas off Chennai, it was during post-monsoon season. Regression analysis showed that chlorophyll concentration had a positive relation with phytoplankton absorption (r2=0.86) during the monsoon season at the stations off Kochi, whereas in the stations off Chennai, high correlation was observed during the post-monsoon season (r2=0.76). The study concerning the variability in, and interconnections among, bio-optical properties is a contribution to our efforts to improve our understanding of the ecological conditions at these study areas. Key words: Bio-optical properties, Detritus matter, Chlorophyll, Phytoplankton, Diatoms 1Nansen Environmental Research Centre(NERCI), India; 2Central Marine Fisheries Research Institute,Kerala, India; 3CSIR-National Institute of Oceanography, Kerala, India; 4Plymouth Marine Laboratory, Plymouth, UK; 5University of East Anglia, Norwich, UK 2023/08/09 (17:30-19:00)
Detecting seasonal shifts in phytoplankton community structure in the eastern Pacific subAntarctic region 1Sarah Le Besque, 1Heather Bouman, 2Mark Moore, 2Adrian Martin Poster Session 2 The Southern Ocean is the only ocean without continental constraints, moving in an uninterrupted flow around Antarctica. This distance from major land masses results in a reduction in the aeolian nutrient input, including iron, a trace metal essential for the metabolic function of phytoplankton. Therefore, most of the Southern Ocean is seen to be iron limited, and characterised by High Nutrient, Low Chlorophyll (HNLC) waters. The remote biomes of the Southern Ocean are highly under-sampled and our understanding of how the community structure and physiology of phytoplankton evolves over the seasonal cycle is poorly known. This weakens our ability to accurately predict how the ecology and productivity of the Southern Ocean will respond under climate change. In this study, we will use a dataset of diagnostic pigments to examine the seasonal cycle of marine phytoplankton in the eastern Pacific subAntarctic region. Ancillary measurements of physical (temperature, mixed layer depths, light), and chemical (macro- and micro-nutrients) will also be presented to identify key environmental variables governing the seasonal shift in phytoplankton communities in this region. The implications of these changes to the fate of carbon fixed in the surface ocean will be discussed. 1University of Oxford, University of Southampton, UK; 2National Oceanography Centre, Southampton, UK 2023/08/10 (17:00-18:30)
Impact Of Regional Weather Events On The Cholera Outbreaks In India 1Sebin John, 2Ranith Rajamohanan Pillai, 3Angus Laurenson, 2Nandini Menon N, 4Midhuna Thayyil Mandodi, 5Grinson George, 6Anas Abdulaziz, 3Bror Jönsson, 7Marie-Fanny Racault, 3Shubha Sathyendranath Poster Session 2 Extreme weather events are increasing due to human-driven and climate-change impacts. Epidemic outbreaks often follow extreme/catastrophic weather events. Changing weather patterns such as increase in surface temperature and rainfall are known to influence the density of Vibrio cholerae in natural water bodies, contributing to cholera outbreaks. This study provides some initial results on the connections between Cholera outbreaks and climate variables. A state-wise database of the water-borne disease occurrences in India during 2009-2020 was created using information from the Integrated Disease Surveillance Programme (IDSP). The IDSP dataset was quality checked to minimize errors, missing values, and duplicate data entry. Spatio-temporal variability in the prevalence of various water-borne diseases was then plotted as choropleth maps using Python. State-wise information on monthly rainfall data obtained from the Indian Meteorological Department was overlaid on the spatio-temporal layer of Cholera outbreaks. Increased Cholera outbreaks (number of cases) and spatial spread along different states of India was related to major tele-connection patterns. During the study, we could relate disease outbreaks with regional weather events along West Bengal (cyclone in May 2009, October 2013), Rajasthan (July 2010-intense rainfall) and the NW/SW states (June-July 2016, El-Nino/Flash floods). Understanding the influence of climate change and extreme weather events on enteric diseases is crucial, because even a minor increase in the risk for Cholera can have significant effects at the global scale. 1University of South Florida, USA; 2Nansen Environmental Research Centre, Kerala, India; 3Plymouth Marine Laboratory, Plymouth, UK; 4Meteorological Department, New Delhi, India; 5ICAR-Central Marine Fisheries Research Institute, Kerala, India; 6CSIR-National Institute of Oceanography, Kerala, India; 7University of East Anglia, Norwich, UK 2023/08/10 (17:00-18:30)
Characterizing the spatial and temporal dynamics of phytoplankton phenology in the British Columbia and Southeast Alaska coastal oceans using satellite ocean colour data 1Sejal Pramlall, 1Maycira Costa, 2Jennifer Jackson, 3Christian Marchese, 3Marta Konik, 3Karyn Suchy, 3Brian Hunt Oral Session 3: Marine Optics & Ocean Colour Phytoplankton phenology is an important ecological indicator that characterises the timing of annually occurring phytoplankton growing periods and has been typically synthesized into a set of indices encompassing the timing, duration, and magnitude of bloom events. Observing changes in phytoplankton phenology requires vast spatial coverage and short temporal frequencies, which is achieved through ocean colour satellite imagery. This study evaluated the GlobColour interpolated product in British Columbia coastal waters via a statistical match-up analysis and a qualitative analysis to determine whether the data reflect the region’s large-scale seasonal trends and latitudinal dynamics. The statistical performance of the GlobColour interpolated product was compared to the original GlobColour and Ocean Colour Climate Change Initiative merged chlorophyll-a products based on in situ observations. A suite of phenological indices were then derived on a pixel-by-pixel basis, and used to partition the study area into phenological bioregions using the Hierarchical Agglomerative Clustering method. The delineated bioregions described region-specific phytoplankton phenological patterns associated with bloom magnitude, frequency, duration, and timing. The GlobColour interpolated product performed relatively well and was comparable to the best performing product for each water type (RMSE = 0.28, r2 = 0.77, MdAD = 1.5, BIAS = 0.90). Four coherent bioregions were identified with distinctive phytoplankton phenological properties: two coastal, one shelf and offshore region. This is the first study to perform a satellite-based 23-year phenology bioregionalization considering multiple bloom events in the British Columbia and SE Alaska coast, thus enabling this heterogenous marine domain to be simplified into coherent spatial regions. 1University of Victoria, Canada; 2Fisheries and Oceans Canada; 3University of British Columbia, Canada 2023/08/10 (09:30-09:45)
Responses of Water Quality Properties to Hurricane Ian in the Southwest Coastal Waters of Florida, US 1Seunghyun Son, 1Paul DiGiacomo, 1Rachel Lazzaro, 1Christine Angelini, 1Prasanjit Dash Poster Session 2 Flooding with heavy precipitations induced by hurricanes can bring a lot of fresh waters with heavy amounts of nutrients, suspended sediments, in/organic carbons, and pollutants from rivers into estuarine and coastal waters, which possibly cause critical damages in coastal marine ecosystems as well as human health. Hurricane Ian, which is the second-dealiest storm to strike the continental US in this century as Category 4 storm, passed over the Florida with strong landfall in the west coast of Fort Myers on September 28, 2022. In this study, in order to investigate responses of water quality properties to hurricane Ian in the Florida coastal waters in 2022, sea surface temperature and ocean color remote sensing data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) are used. Higher spatial resolution (3–10 m) satellite imageries from Sentinel-2 MultiSpectral Instrument (MSI) and commercial sensor, Planet Scope, are also used to investigate fine spatial features of changes in water quality properties induced by the strong hurricane impacts in the west coastal waters of Fort Myer including Charlotte Bay, particularly by floodings (with suspended sediments, colored dissolved organic materials, pollutants) from Myakka River, Peace River and Caloosathatchee River. In addition, all available in situ Chl-a and other water quality measurements in the water quality monitoring stations collected by a consortium of entities in the study region are compared with the satellite-measured products. 1NOAA/NESDIS/STAR, USA 2023/08/10 (17:00-18:30)
Potential bloom-forming phytoplankton species in Indian waters 1Shalini Sarkar ,1Samir R. Damare Poster Session 2 The monsoon patterns play a significant role in making the Indian Ocean a unique system and thus distinct from the other global oceans. A sudden increase in phytoplankton cell density in a particular area is termed as algal bloom. Blooms are erratic and are caused by an amalgamation of factors. Harmful algal blooms are gaining the limelight all across the globe due to their havoc-creating capabilities. The toxins bioaccumulate along the food chain and thus lead to hospitalization and even death in certain cases. India has also seen a rise in bloom events in the last five decades, although the frequency is less than the occurrences in Pacific or Atlantic waters. Dinoflagellate blooms dominate the west coast of India, while diatom blooms are dominant on the east coast. To have an idea about the factors causing blooms and the species involved, off-shore surface water was collected from the Candolim Time Series Stations (CaTS) in the Arabian Seaduring January-February, 2023. Major potential toxin producers like Procentrum sp., Gymnodinium sp. were observed in the water samples. Ceratium furca followed by Ceratium fusus, were the dominant species based on the microscopic observations. Other dinoflagellate species, like Protoperidinium sp., Ornithoceros sp. and Alexandrium sp. were also present, but comparatively inlower numbers. In order to check the ability to produce toxins, these plankton species are being grown in the laboratory. The toxin production will be confirmed by LCMS-MS analysis of the cell extracts of purified cultures. 1CSIR-National Institute of Oceanography, Goa, India 2023/08/10 (17:00-18:30)
Juvenile fisheries dynamics in relation to plankton abundance in the Naf river estuary, Bangladesh 1Shashowti Chowdhury Riya, 1Subrata Sarkere Poster Session 2 Present study aimed to understand the juvenile fisheries community dynamics in relation to plankton abundance in the Naf river estuary. Data on plankton and juvenile fisheries were collected from January 2022 to December 2022. In addition, during this study environmental data (i.e. biotic and abiotic variables) were also collected. The study found that the Naf river estuary is dominated by diatom functional group of phytoplankton. Zooplankton communities of Naf river include copepod, mysids, isopods, sagitta, crabs, small benthic organisms, squids, crustaceans, mollusk, worms, benthic invertebrates, detritus, zooplankton and larval fish. During the study, occurrence of more than 30 species of commercially important juvenile fish species was observed in the Naf River Estuary. Occurrence of about 17 juvenile species was frequent from April to July. These juvenile fish species include Coilia spp., Epinephalus spp., Terapon spp., Sillago sp., Alectis sp., Parastromates sp., Selene sp., Lobotes sp., Pomodasys sp., Acanthopagrus sp, Johnius sp, Polynemus sp, Drepane sp, Scatophagus sp, Eupleurogrammus sp, Pampus sp and Mugil sp. Our analysis found that occurrence of juvenile fisheries is driven by the abundance of phytoplankton and zooplankton. On the other hand the community dynamics of phytoplankton is strongly related to salinity and nutrients. This study will serve as the guide line for the conservation initiatives of juvenile fisheries in the Naf River estuary. 1Shahjalal University of Science and Technology, Bangladesh 2023/08/10 (17:00-18:30)
Satellite-guided individual based modelling for spatial distribution of fish: Atlantic mackerel as an example 1Shovonlal Roy, 1Robin Boyd, 1Richard Sibly, 2Kieran Hyder, 2Nicola Walker,2Robert Thorpe Oral Session 6: Size and ecosystem structure of aquatic communities Coastal waters support 90% of marine species and are areas of key socio-economic importance to more than three billion people who rely on coastal biodiversity for food, aquaculture, and tourism. However, increased coastal ocean usage and climate change have led to harmful algal blooms (HABs) occurring more frequently and severely. The Southern Benguela system is a prime example, with a yessotoxin-producing bloom in 2019 resulting in millions of abalone stock dying and an estimated financial loss of $33 million. The accurate reporting of coastal ocean chlorophyll-a (Chl-a) concentration (a proxy for phytoplankton biomass) is crucial to our ability to better detect, monitor and understand these HAB events. Existing Chl-a algorithms have limitations, particularly in waters with very-high or very-low phytoplankton biomass (<1 to >100 mg/m-3), such as the southern Benguela and other upwelling systems. Thus it is common practice to develop regionally specific algorithms (Smith & Bernard, 2018). Due to the complexity of developing these models, they are often designed to work with a single imaging platform, which limits their availability and usability for consistent long-term monitoring. To address these limitations, we propose a deep learning-based Chl-a model that can provide regionally accurate Chl-a estimates across multiple remote sensing platforms (Sentinel-3, VIIRS, MODIS, etc.). The model enables robust, consistent, and high-frequency monitoring of potential HAB events by exploiting temporal heterogeneity and spectral similarities of various platforms. This leads to an improved understanding and potential mitigation of the impacts of HABs on coastal ecosystems and communities. 1University of Reading, UK; 2Centre for Environment, Fisheries and Aquaculture Science, UK 2023/08/11 (10:00-10:15)
Climate refugees of Kuttanad in Kerala, India and elsewhere: how can science help build resilience against weather extremes? 1Shubha Sathyendranath, 2,3Nandini Menon, 5Anas Abdulaziz, 4Grinson George, 1Gemma Kulk, 2Jasmin C, 1Robert J W Brewin Poster Session 2 Kuttanad, often referred to as the rice bowl of Kerala, is a below-sea-level agrarian region in the Vembanad Kol wetland system (A Ramsar site). A recent newspaper article reports that some 15% of the population of Kuttanad have become climate refugees. Those who have moved away from the region cite increased frequency of floods and water logging as the primary reason for abandoning their traditional life style and ancestral land. With changing climate, extreme water-related events such as droughts and floods are expected to increase in frequency and intensity the world over. In addition to the physical danger from such events, there the often-less-appreciated threats to human health that appear in their wake. What can Earth observations do to help build resilience against such threats, and optimise response in the event of disasters? One defence against floods associated with rising sea level is to promote re-introduction of natural barriers such as mangroves, where they have been removed, and Earth observation can provide tools for monitoring the extent of, and changes in, such natural defences. Operational Earth observation satellites can be used for monitoring the extent and location of floods, to facilitate disaster response. Water quality can be monitored using satellites, and in the event of a disaster, near-real-time monitoring can be used to alert citizens of areas of poor water quality, and in some instances, associated risks of water-borne diseases. Furthermore, citizen science can be used to complement Earth observations and to update dynamically the health and sanitation status of the flooded and surrounding areas. 1Plymouth Marine Laboratory, Plymouth, Devon, UK; 2Nansen Environmental Research Centre (India), Kochi, 682506, India; 3Trevor Platt Science Foundation, Kochi, 682 018, India; 4ICAR-Central Marine Fisheries Research Institute, Kochi, 682018, India; 5CSIR-National Institute of Oceanography, Regional Centre, Kochi, India 2023/08/10 (17:00-18:30)
Global patterns and trends in marine primary production 1Shubha Sathyendranath, 1Thomas Jackson, 1Gemma Kulk, 1Robert Brewin, 1Bror Jönsson, 1Christina Kong, 1Laine, 1James Dingle, 1Heather Bouman, 1Dionysios Raitsos, 1Stella Psarra, 1Eleni Livanou, 1Didier Ramon, 1François Steinmetz, 1Giorgio Dall ‘Olmo1Tihomir Kostadinov, 1Cécile Rousseaux, 1Mick Follows, 1Trevor Platt Poster Session 2 Time series data of Ocean Colour Climate Change Initiative products of chlorophyll-a concentration, de Boyet Montégut mixed-layer depth, and PAR from NASA were combined with photosynthesis-irradiance parameters and chlorophyll depth profile parameters established from in situ observations, to calculate two sets of marine production calculation at the global scale, as part of CBIOMES and BICEP projects. The first set of calculations were for the full water column, to the base of the euphotic zone, and incorporated vertical structure in chlorophyll concentration, using a Gaussian parameterisation with a fixed background. The second set of calculations assumed a uniform depth profile for chlorophyll concentrations and were limited to the mixed layer. Analysis showed that water-column primary production trends varied with location, with significant positive or negative trends in some parts of the ocean, and insignificant trends in other regions. When the fraction of production in the mixed layer relative to water-column production was studied for the Arctic, the Red Sea, the Aegean Sea, the Atlantic and the Pacific, regional differences were observed. For these regions, the fractional production in the mixed layer increased with increase in the fraction of micro-phytoplankton to total phytoplankton carbon in the mixed layer. Regions with low microplankton fraction probably contribute to export production through production in the deep chlorophyll maximum, which is below the mixed layer, and fuelled by a supply of deep nutrients. On the other hand, regions with relatively higher proportions of micro-phytoplankton probably contribute to export production through rapid sinking of large phytoplankton cells. 1Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK 2023/08/10 (17:00-18:30)
Understanding photoacclimation effects on Chl:C ratio in the S. Ocean: modelling considerations and insights into seasonal assemblage composition 1Sifiso Mpapane, 1Lisl Lain, 1Sandy Thomalla Poster Session 1 Chlorophyll:carbon (Chla:C) ratios can reveal important information on adjustments in phytoplankton community composition and/or physiological acclimation to environmental conditions. As such, it is important to be able to accurately retrieve this information from ocean colour remote sensing. Jackson et al (2017) detail an exact solution for modelling photoacclimation of the Chla:C ratio in phytoplankton using SeaWiFs chlorophyll and monthly mean PAR, and then apply the result to the OC-CCI Chla data product. Recent work however suggests that OC-CCI Chla product may overestimate Chla concentrations in the Southern Ocean, particularly in winter. Our approach is to instead apply the Jackson et al (2017) solution to MODIS Chla, in which we have higher confidence in this region (Moutier et al., 2019), and daily PAR. This approach will allow us to investigate environmental impacts on Chl:C variability even at subseasonal time scales, which are considered dominant in driving phytoplankton dynamics in the Southern Ocean (Ryan-Keogh et al., 2018). This investigation is especially important given that phytoplankton growth is known to be seasonally light limited in the Southern Ocean. Being able to account for photoacclimation-driven variability in Chla:C in the context of satellite and in situ observations can inform on seasonal variability in particulate assemblage composition and the interpretation of bulk satellite products (such as particulate backscatter), towards improving our ability to quantifying phytoplankton C from space. As this work is ongoing, in this presentation progress towards this goal will be shared in the context of the rationale and motivation for the work. 1Southern Carbon & Climate Observatory (SOCCO), Council for Scientific and Industrial Research (CSIR), and University of Cape Town 2023/08/09 (17:30-19:00)
Seagrass mapping using remote sensing for identification of critical dugong habitats in Indian 1Sohom Seal, 2Mini Raman, 3K Sivakumar, 1J A Johnson Poster Session 1 Dugongs (Dugong dugon) are one of the four surviving species in the Order Sirenia and the only extant exclusively herbivorous marine mammal. Though having a meagre estimate population of 200-250 individuals, India retains the largest dugong population in south Asia and thus plays a significant role in dugong conservation at a regional scale. They are primary consumers, specialized in exploiting seagrass herbivory in terms of biomass and food quality (nitrogen, water-soluble carbohydrates, structural carbohydrate and fibre, secondary metabolites, etc.). Of about 72 different seagrass species found worldwide, India houses 15 of them along the isolated locations of coasts, lagoons, backwaters, and estuaries. Recent reports on declining population trends or functional extinction of dugongs identified high and positive collinearity with the loss of seagrass habitats. With the increasing environmental impacts of climate change on individual species, understanding the relationship between habitat factors is an essential step towards predicting the distribution of that species. Therefore, with an aim to identify critical dugong habitats, we tried to map the seagrasses in selected dugong habitats in India namely South Andamans (SA), Andaman & Nicobar Island, north Palk Bay (PB) and Gulf of Mannar (GoM), Tamil Nadu using remote sensing and GIS technologies. We used the Google Earth Engine platform to map the seagrasses of these regions with Sentinel-2 imageries. Mapping accuracy ranges from 70 to 96% depending upon the classification algorithm used and the condition of water transparency. 1Wildlife Institute of India, P.O. Chandrabani, Dehradun-248001, India; 2Space Applications Centre, Ahmedabad-380015, India; 3Department of Ecology and Environmental Sciences, School of Life Sciences, Pondicherry University, Puducherry 605 014, India 2023/08/09 (17:30-19:00)
The Partnership for Observation of the Global Ocean (POGO): Advancing sustained ocean observations for societal benefitr 1Sophie Seeyave, 1Lilian Krug, 1Fiona Beckman Poster Session 1 The ocean produces half of the world's oxygen, most of its fresh water and much of its food. It regulates climate and weather; is critical to the cycling of heat, water and carbon; and is the source of huge biodiversity. However, far too little is known about the state and functioning of the ocean. Motivated by a common belief that advancing scientific understanding of the ocean is rooted in making systematic, high quality measurements, the Directors of major oceanographic institutions from around the world came together in 1999 and established the Partnership for Observation of the Global Ocean (POGO). POGO has evolved and grown over the past 24 years, but it remains true to its original mission: to expand international support for ocean observing, through innovation of the ocean observing system, capacity development and outreach/advocacy. Today, POGO brings together 55 oceanographic institutes from 29 countries to plan joint actions to advance sustained ocean observations for societal benefit. Over the years, POGO has developed and supported projects on technological innovation; fostered working groups on specific aspects, priorities or challenges related to ocean observing; provided training and capacity development opportunities for over 1,200 early-career scientists in developing countries; created and nurtured an alumni network; highlighted the need for ocean observations to policymakers, the general public and schools, through publications, high-level declarations, public events and citizen science, education and outreach projects. An overview of POGO’s objectives, impact and current activities will be presented. 1Partnership for Observation of the Global Ocean (POGO), USA 2023/08/09 (17:30-19:00)
Study of Plankton dynamics in the Southern Ocean ecosystem: Biogeochemical implications 1Sreerag A, 1Rajani Kanta Mishra Poster Session 1 In the Southern Ocean marine ecosystem, the sink of CO2 and climate changes are associated with the shifting of the plankton communities with potentially wide-ranging biogeochemical effects. The physical-chemical parameters such as the temperature, photosynthetic available radiation (PAR), and micronutrient collectively influence to adjust the plankton diversity. Significant latitudinal phytoplankton variations were observed at the Subtropical Front (STF), Sub Antarctic Front (SAF), Polar Front (PF), and South of Polar Front (SPF) during the austral summer of 2019. The Fragillariopsis spp. of diatoms was dominant and followed by Chaetoceros sp. and Coscinodiscus sp. at the surface along the Sub-Antarctic and Polar Fronts. While the Gyrodinium spp. of flagellates was most dominant, followed by Protoperidinium sp. and Amphidinium sp. at the Sub-Tropical Front. Zooplankton biovolume in the upper 200m varied between 0.71 – 10 ml 100 m-3. Relatively higher zooplankton biovolume and numerical abundance have been found in the SAF than in PF. The nitrate (NO3-), phosphate (PO43−), and silicate (SiO4) concentrations were found high towards higher latitudes. Lower zooplankton biovolume was associated with high Chlorophyll a (Chl-a) concentration may have significant negative consequences for higher trophic levels in the PF. The result obtained suggests that the phytoplankton biomass and community composition vary along the frontal regions and have the combined impact of governing variables. 1National Centre for Polar and Ocean Research 2023/08/09 (17:30-19:00)
Primary-productivity in Upwelling Systems (PRIMUS) 1Steve Groom, 1Bror Jönsson, 1Shubha Sathyendranath, 1Tom Jackson, 1Peter Land, 1Gemma Kulk, 1Kim Hockley, 2Alvarez-Salgado, 3Javier Arístegui, 3Nauzet Hernandez, 4Vanda Brotas, 4Catarina Guerreiro, 4Ana Brito, 4Mara Gomes, 4Afonso Ferreira, 5Paulo Oliveira, 5Susana Garrido, 6Christo Whittle, 6Marie Smith, 7Marco Restano, 7Jérôme Benveniste Oral Session 1: Physical and biological interactions The ESA-supported Primary-productivity in Upwelling Systems (PRIMUS) project aims to provide the best possible characterisation of net primary productivity (NPP) and its relationship to upwelling in Atlantic Eastern Boundary Upwelling Systems (EBUS), including the Iberian/Canary and Benguela systems. It has created a 25-year time series of 1-km satellite-derived NPP over the Atlantic, using two models: Platt-Sathyendranath and Smyth et al (2005). An experimental NPP product, at higher-resolution (300m) using the unique capabilities of the MERIS and OLCI satellite sensors has also been produced. PRIMUS is using these data to advance analyses of Atlantic EBUS including temporal and spatial variability in NPP and its statistical relationship to upwelling and climate indices (such as the North Atlantic Oscillation). PRIMUS is also conducting eight further science cases in specific science areas / regional settings: aquaculture in Galicia; fisheries and eutrophication in the Portuguese upwelling region; potential EBUS impacts on ocean carbon pools; Lagrangian estimates of NPP; and air-sea interaction and acidification impacts. Science cases will make use of EO and in situ data, as well as numerical model outputs (freely available through the EU’s Copernicus and elsewhere) to investigate the 4D character of EBUS, for example, linking Lagrangian NPP with sediment traps samples at depth. PRIMUS is also conducting demonstrations that transfer science into solutions for society, working together with scientific, agency, policy and commercial “early-adopters”, building on three science case studies (EBUS and aquaculture; fisheries; and eutrophication monitoring). Furthermore, evaluating transition of data production to operational initiatives such as Copernicus and GMES and Africa and the potential for data exploitation by the European and international ecosystem modelling community. This communication will present results from the 25-year NPP time series and high resolution NPP computations as well as selected science cases. 1Plymouth Marine Laboratory, UK; 2The Spanish National Research Council (CSIC) -IIM, Spain; 3University of Las Palmas de Gran Canaria Spain; 4Faculdade de Ciências da Universidade de Lisboa, Portugal; 5Instituto Português do Mar e da Atmosfera, Portugal; 6Council for Scientific and Industrial Research, South Africa; 7European Space Agency and European Center for Earth Observation (ESA-ESRIN), Italy 2023/08/09 (11:45-12:00)
Integration of socio-ecological data for MPA zoning: An example from the south-east coast of Bangladesh 1Subrata Sarker, 1Md jalilur Rahman, 1Muhammad Mizanur Rahman, 1Morgina Akter, 1Md Shajjadur Rahman, 1Md Abdul Wahab Oral Session 6: Size and ecosystem structure of aquatic communities Having a biodiversity rich maritime area of about 118000 km2, Bangladesh is facing the challenges of environmental change and over exploitation. Thus, conservation efforts are urgent need for the coastal and marine ecosystems of Bangladesh. Taking this into account this study aims to assess the suitability of Saint Martin – Teknaf Peninsula of south-east coastal zone of Bangladesh to declare as marine protected area (MPA) considering four protection levels (i.e. no entry - no take zone; entry - no take zone; partial and general reserve). Primary data on socio-economic status and biodiversity were collected through a yearlong field study. We used the spatial multiple-criteria analysis technique to determine the suitability of Saint Martin – Teknaf Peninsula to declare as MPA. We found that local communities are mainly involved with fishing and tourism based activities for their livelihood. The study also found about 900 species which includes critically endangered, endangered and vulnerable species. Both social and biodiversity data suggest that conservation efforts are required for Saint Martin – Teknaf Peninsula. Present study identified 2992.29 km2 potential area of Saint Maritn – Teknaf Peninsula for MPA declaration. Potential no-entry, no-take zone covers an area of 44.37 km2 while entry, no-take; partial reserve and general reserve cover an area of 710.92, 1436 and 801 km2 area respectively. Our study will serve as a model example to delineate the MPA zones with different protection levels for tropical and sub-tropical marine systems. 1Department of Oceanography, Shahjalal University of Science and Technology, Sylhet, Bangladesh 2023/08/11 (09:30-09:45)
Classifying global oceans based on the impact of factors affecting primary productivity 1Sudeep Das, 1Rahul Deogharia, 1Sourav Sil Poster Session 1 Classification of ocean ecosystems needs a clear and unbiased methodology to identify study areas and compare patterns and processes within them. We present a method of unsupervised learning to identify global marine ecological regions based on key factors impacting productivity. This classification uses 14 years monthly data of biogeochemical parameters from satellite observations and established models, instead of commonly used climatology data. We calculate correlation coefficients of chlorophyll-a with limiting factors such as PAR (Photosynthetically Active Radiation), nitrate, and iron for the segregation. The data was analyzed using k-means clustering technique to divide the world’s oceans into six types of basins. The clusters were divided roughly based on their trophic levels. Clusters 1 and 2 represented eutrophic regions with a low and high correlation with PAR, respectively. These were situated near the equator (0–10°) and higher latitudes (>50°). Cluster 3 revealed mesotrophic areas with a significant positive correlation with nitrate and iron, and were located on the western boundaries of the oceans. Cluster 4 showed mesotrophic regions with higher nitrate dependency. Clusters 5 and 6 showed oligotrophic regions with positive nitrate correlation and negative PAR correlation, indicating nitrate and PAR as the primary driving and inhibiting factor, respectively. These two clusters generally exist inside the major downwelling gyres, and were governed by the effect of stratification. This categorization method could enhance comprehension and surveillance of ocean ecosystems by identifying the main factors affecting productivity and, additionally, the work can be expanded to incorporate other crucial oceanic factors and processes. 1IIT Bhubaneswar, India 2023/08/09 (17:30-19:00)
Long-term patterns of chlorophyll-a bloom estimated by new switching algorithm and correlation analysis between environmental factor and bloom parameter in the eastern Yellow Sea 1Sungjun Kim, 1Sang Heon Lee Poster Session 1 Satellite-derived chlorophyll-a concentration (Chl-a) has been used as an essential indicator for wide spatial and temporal changes in environmental factors. However, in optically complex water such as the eastern Yellow Sea (hereafter, EYS), the standard algorithm for satellite-derived Chl-a could overestimate the Chl-a. Therefore, the main objectives in this study are to develop a new Chl-a algorithm suitable for the EYS and investigate long-term Chl-a spring bloom patterns in the EYS. The new Chl-a algorithm for the EYS was developed from a switching approach according to turbidity condition based on normalized water-leaving radiance at the 555 wavelength (nLw555). The results show that Chl-a data based on the new switching Chl-a algorithm was well-matched (R2 = 0.83 and RMSLE = 0.26) with in situ Chl-a in comparison to the standard algorithm. The spring bloom initiation time ranged from 7 March to 13 April with an average of 24 March (S.D. = ± 10 days) and the spring bloom peak Chl-a ranged from 1.72 μg L-1 to 3.90 μg L-1 with an average of 2.65 μg L-1 (S.D. = ± 0.78 μg L-1) in the EYS from 2003 to 2020. The spring bloom duration ranged from 26 days to 96 days with an average of 62 days (S.D. = ± 22 days) during the study period. Interannual variations in the spring bloom patterns are closely (p < 0.01) associated with changes in physical environmental factors in the EYS. Especially, the spring bloom initiation time largely depends on the light condition. 1Pusan National University, South Korea 2023/08/09 (17:30-19:00)
Defining a range of chlorophyll-a concentration for characterizing algal bloom conditions to generate operational ecosystem services for Indian coastal waters 1Susmita Raulo, 1Alakes Samanta, 1Sanjiba Kumar Baliarsingh, 1Sudheer Joseph, 1T M Balakrishnan Nair Poster Session 1 The frequency of algal blooms and resultant water quality deterioration is on the rise in different parts of the world ocean. The algal bloom occurrences have increased over the years in the Indian coastal waters attributed to a multitude of factors such as natural processes, anthropogenic perturbations, climate change, etc. Several in-situ studies have reported algal bloom events from time to time. After the introduction of ocean colour satellites, many studies have also characterized spatio-temporal extent of algal blooms. Both in-situ and satellite studies use chlorophyll-a concentration (proxy of phytoplankton biomass) to define bloom conditions. Unlike, open ocean waters, there is no defined range of chlorophyll-a concentration for the Indian coastal waters to define the algal bloom conditions, which is an important requisite in generating operational marine ecosystem services such as algal bloom information, eutrophication, potential fishing zone advisories, etc. This study defines a range of chlorophyll-a concentration for the Indian coastal waters by considering the variability during bloom events as described in the previous reports, causative phytoplankton species in relation to the biomass during bloom conditions, satellite-retrieved long-term trends, and potential algal bloom hotspots based on the frequency of reoccurrence. The long-term analysis of chlorophyll-a carried out in this study is based on the climatology (monthly, seasonal, and annual) estimates retrieved from the Moderate Resolution Imaging Spectroradiometer–Aqua, covering a 2-degree zone of the sea from the Indian coastline. This study aids in characterizing the nature of algal blooms as harmful or eco-friendly in the Indian coastal waters. 1Indian National Centre for Ocean Information Services, India 2023/08/09 (17:30-19:00)
Bio-optical properties and dissolved inorganic nutrients of the Amazon Reef System 1Thais Andrade Galvao de Medeiros, 1Milton Kampel Poster Session 1 The Amazon Reef System (ARS) is a mesophotic coral ecosystem offshore of the Amazon River, which extends ~1,000 km along the Amazon shelf and covers an area > 50,000 km². This ecosystem is mainly composed of a biogenic structure built of coralline algae, rhodoliths and rhodoliths beds, with occurrences of black corals, octocorals and scleractinians, living in depths between 70-220 m. This study aims to describe some bio-optical properties and dissolved inorganic nutrients (ammonia, nitrite, nitrate (DIN)) distribution sampled in the austral winter of 2017. The mean and standard deviation of colored dissolved organic matter absorption coefficient at 440 nm (aCDOM), surface chlorophyll-a concentrations (Chl-a) and surface DIN were respectively 0.15 ± 0.11m-1, 0.50 ± 0.38 mg·m-3 and 2.21 ± 1.94 mmol L-1. For relatively deeper waters (> 100m), mean Chl-a and DIN were 0.42 ± 0.28 mg·m-3 and 4.74 ± 9.26, respectively. The empirical relationship between Chl-a and the phytoplankton absorption coefficient at 440 nm diverged from reference models, suggesting differences in phytoplankton size structure and populations. The relationship between Sf and DIN showed that phytoplankton with small cells predominated in areas with low DIN. As observed in coastal waters, the total non-water absorption coefficient at 440 nm was dominated by CDOM, with its slope corresponding to typical coastal areas (0.013 ± 0.003 nm-1). The findings presented here extend our knowledge of this important but still poorly known Amazon Reef System and its optical environment. 1National Institute for Space Research (INPE), Brazil 2023/08/09 (17:30-19:00)
Biogeochemical dynamics of the central South Pacific: a study based on biogeochemical Argo floats 1Thomas Hermilly,1Elodie Martinez, 2Julia Uitz, 3Catherine Schmechtig Poster Session 1 The central South Pacific Ocean is characterised by very low nutrient concentration in the upper-layer, making it the most extended oligotrophic region of the global ocean. These clear waters let the solar irradiance penetrate deeply into the water column, and allow phytoplankton to grow in the subsurface layers, at an optimal depth for light and nutrients. Consequently, despite the weak surface biomass observed by satellites, this oligotrophic region could be an important contributor to the global carbon balance thanks to its tremendous size. However, because the South Pacific Ocean remains one of the least sampled areas of the global ocean regarding biogeochemical (BGC) measurements, a lot of uncertainties remain on the spatial distribution of phytoplankton in the subsurface, as well as its temporal variability. This also holds for the identification of the physical processes involved in the phytoplankton dynamics which may strongly vary in space and time. To investigate the phytoplankton dynamics and the underlying physical-BGC processes in the central South Pacific Ocean, we investigated temperature, salinity, chlorophyll-a fluorescence, backscattering at 700 nm and downwelling photosynthetically available radiation observations from 15 BGC Argo floats which have drifted from 2015 to 2023 over [10°S - 40°S]. With this dataset, we propose: (1) a classification of the chlorophyll-a profiles in contrasted regions of the South Pacific Ocean, based on their vertical distribution. The temporal variability of photoacclimation on the chlorophyll-a signal was considered; (2) a characterisation of the ocean dynamics that impact the phytoplankton biomass distribution and variability in these areas. 1Laboratoire d'Océanographie Physique et Spatiale (Brest), France; 2Laboratoire d'Océanographie de Villefranche, France; 3Centre national de la recherche scientifique (CNRS), France 2023/08/09 (17:30-19:00)
Remote Sensing of Ocean Colour for Climate Research: The requirements, status and future from a CCI perspective 1Thomas Jackson, 1Steve Groom, 1Shubha Sathyendranath, 2Robert Brewin, 3Vanda Brotas Poster Session 1 Measurements of Ocean Colour and the geophysical products derived from them are essential to studying phytoplankton dynamics over long timescales, processes linking phytoplankton and marine biogeochemistry, the global carbon cycle, and the response of the marine ecosystem to climate forcing. Ocean Colour data is also utilised for operational and near-real-time monitoring of the oceans with short term features such as eutrophication, harmful algal blooms, and sediment plumes being visible. The requirements from the Ocean Colour community on data quality, availability, stability and traceability are increasing and of great importance as we try to make forecasts of an increasingly perturbed earth system. By 2029 the record should start to be of sufficient duration to discriminate climate change impacts from natural variability, at least in some regions. The ESA Ocean Colour Climate Change Initiative has spent the last decade striving to meet the requirements of the community to provide a high quality climate data record that is suitable for a wide range of applications and scientific investigations. This work summarises the current requirements, status and future prospects for climate quality ocean colour data from the viewpoint of OC-CCI. It reviews the user requirements in terms of products and uncertainty characteristics and then assesses the latest products against those requirements, discussing challenges, solutions and lessons learnt along the way. We go on to outline expected future developments and goals building on the current OC-CCI achievements. 1Plymouth Marine Laboratory, UK; 2University of Exeter, UK; 3Universidade de Lisboa, Portugal 2023/08/09 (17:30-19:00)
Trends and trajectories of phytoplankton primary production and bloom phenology in the Southern Ocean 1Thomas Ryan-Keogh, 1Sandy Thomalla, 2Pedro Monteiro, 1Sarah Nicholson, 3Marie Smith, 4Alessandro Tagliabue Oral Session 4: Physiological ecology of marine phytoplankton Climate change is eliciting widespread adjustments to the physical and chemical environment of the oceans, which affects the distribution and seasonal cycle of phytoplankton primary production (NPP). This in turn impacts ecosystem function and the transfer of carbon, energy and nutrients through food webs with complex feedbacks on ocean biogeochemistry and climate. Remote sensing data products such as the ocean colour climate change initiative provide an opportunity to investigate long term trends and identify thresholds of tipping points and abrupt change. Here we developed two global datasets of phytoplankton NPP and bloom phenology. Whilst they are produced globally, we focus here on the Southern Ocean (SO), where the biological carbon pump is considered to play a particularly important role in global climate. Compounding this, the SO is expressing a particular sensitivity to climate change, with physico-chemical alterations already evident. Indeed, the majority of NPP algorithms report that almost two thirds of the SO are typified by significant negative trends over the past 24 years, with evidence of a significant multi-decadal increase in phytoplankton iron stress potentially the cause. Concomitant with these declines are significant shifts in the timing, duration and characteristics of variability of phytoplankton seasonal blooms. The majority of these trends differ to those currently being predicted by earth system models, suggesting that they may be underestimating ongoing change in the SO. Adjustments of this magnitude will not only impact energy transfer to higher trophic levels but could also impact global climate by altering natural carbon uptake. 1 Southern Ocean Carbon-Climate Observatory, CSIR, South Africa; 2School for Climate Studies, Stellenbosch University, South Africa; 3Coastal Systems and Earth Observation Group, CSIR, South Africa; Department of Earth, Ocean and Ecological Sciences, University of Liverpool, UK 2023/08/10 (11:00-11:30)
Detection and tracking of large marine litter based on high-resolution remote sensing time series, machine learning, and ocean current modelling 1Tobias Weiss, 1Mathias Bochow Poster Session 2 Marine debris is a severe environmental problem. It originates from many sources and causes a wide spectrum of environmental, economic, safety, health and cultural impacts. Millions of tonnes enter the oceans every year and tackling the issue is gaining momentum at all levels. Monitoring floating debris from Earth’s surface is difficult as it is impossible to see much of the ocean at one time. Our project presents an approach to detect and track floating marine debris such as lost fishing nets, debris aggregations or patches based on high-resolution remote sensing time series, machine learning, and ocean current modelling. The goal is to obtain more reliable data regarding quantity, position, material properties and sources of litter as well as to address the lack of understanding of floating debris behaviour in the open sea due to the limited monitoring capabilities (Garaba and Dierssen, 2018). In order to achieve this goal, a convolutional neural network was trained with a hand-labeled dataset of objects floating on the sea surface extracted from Planet satellite imagery, to learn the spatial characteristics of these objects. A software pipeline has been developed to automatically retrieve, process and analyse large amounts of satellite images and enable continuous monitoring. As identifying floating objects in the marine environment from space remains a challenging and difficult task and ground truthing is near to impossible, we further apply a mechanism to find matching objects on time series of satellite images using an ocean current model as well as different image processing techniques. 1GFZ German Research Centre for Geosciences, Germany 2023/08/10 (17:00-18:30)
Time series analysis of SST over water quality for water supply in desalination 1Tomás Ignacio Acuna Poster Session 2 The quality of seawater in desalination is a critical aspect to promote new sources of unconventional water resources for drinking water. For these purposes, in this work sea surface temperature was analyzed to study the seasonal temperature dynamics using Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperature (SST) and Global Ocean 1/12° Physics Analysis to determine the main regimes of change and periods of coastal upwelling that affect the water quality of the largest desalination plant in Chile. The results indicate that temperature is a key indicator to predict the behavior of water quality, allowing better decision-making and reducing the operating costs (OPEX) of the pretreatment system. 1BloomAlert, Santiago, Region Metropolitana, Chile 2023/08/10 (17:00-18:30)
Variability and consistency of phytoplankton size structure in Atlantic Ocean Regions 1Vanda Brotas, 1Andreia Tracana, 1Vera Veloso, 2Glen Tarran, 1Afonso Ferreira, 1Catarina Guerreiro, 2E. Mallcolm Woodward, 2Steve Groom Poster Session 2 Inferring oceanic phytoplankton biomass by remote sensing of ocean colour through the estimation of Chlorophyll a, a phytoplankton biomass proxy, is acknowledged by the scientific community as having reached a mature state. However, understanding and monitoring phytoplankton community structure across large spatial and temporal scales still represents a challenge to Earth Observation. The need for in situ data is widely acknowledged. The Atlantic Meridional Transect (AMT) program ( provides an opportunity to observe phytoplankton community size structure in a number of Atlantic regions between 50 N and 50 S. This work presents cell abundance of phytoplankton taxa on three cruises, AMT 25, 28 and 29 (in 2015, 2018 and 2019, respectively) using flow cytometer and microscopic observations, as well as the pigment composition of the community, from HPLC pigments, to quantify taxonomic groups and size classes. The community size structure showed a clear inter-annual consistency at the large spatial scale, with a dominance of picoplankton cyanobacteria in oceanic gyres, an increase in all groups in the equatorial upwelling region, and high biomass of microplankton size class at higher latitudes. However, an intrinsic variability was found amongst the bloom-forming species of Diatoms and Dinoflagellates, identified by microscopy, as compared to results from the earlier AMTs (1995-1998). Furthermore, the measurement of biovolume, carbon, diagnostic pigments, per taxonomic group, gave crucial information needed to bridge the gap between ocean colour detection of size classes and carbon biomass of the different phytoplankton functional types. 1Faculty of Sciences University of Lisbon, UK; 2Plymouth Marine Laboratory, UK 2023/08/10 (17:00-18:30)
Marine Ecological Time Series “Estación Permanente de Estudios Ambientales (EPEA)”– Southwestern Atlantic 1,2Vivian Lutz, 2Lucrecia Allega, 2Carla Berghoff, 2Mario Carignan, 1,2Georgina Cepeda, 2Ezequiel Cozzolino, 1,2Daniela A. del Valle, 1,2Marina Díaz, 1,2Rosana DiMauro, 1,2Marina Do Souto, 1,2Lucia Epherra, 1Jorge Fernández, 1Micaela Giorgini, 1Constanza Hozbor, 1Ezequiel Leonarduzzi, 1,2Moira Luz Clara, 1Reinaldo A. Maenza, 1Nora Montoya, 1Silvia Peresutti, 1Guillermina Ruiz, 1Valeria Segura, 1Ricardo Silva, 1Rubén Negri Poster Session 2 Marine ecological time series (METS), involving environmental and biological sampling from a ship, offer crucial information to attempt to discern natural variations from those influenced by global change. The program “Dynamics of Marine Plankton and Climate Change” from INIDEP carries out studies at different METS in the southwestern Atlantic: the coastal stations EPEA and El Veril, and three sections COSTAL (coast to shelf-break). EPEA (38º28'S - 57º41'W) has been systematically sampled, ideally on a monthly frequency, since February 2000. An ensemble of physical, bio-optical and biogeochemical variables, all components of the plankton (bacterio-, phyto-, zoo-, and ichtyo-plankton), as well as some physiological processes (primary production, nutritional condition of larvae) are studied at this site. New relevant problematics have been addressed along the way; e.g., ocean acidification and micro-plastic contamination. EPEA also facilitates the collection of in situ data to validate satellite information. Here we present the work being developed at EPEA (e.g., variables sampled, thesis and publications produced). EPEA is still young (24 years) to elucidate climate change effects; nevertheless a basic understanding of the behavior of the system and its variability has emerged. Throughout the time series some trends of change have been detected; chlorophyll-a has increased, especially in the fraction associated to small-size phytoplankton, and its seasonality shows a conspicuous feature with the highest values towards end of winter. The continuation in time of observations at EPEA, integrated to others obtained in the region and global ocean, contributes knowledge required to interpret variations at a climatic scale. 1National Scientific and Technical Research Council, Argentina; 2National Institute for Fisheries Research and Development INIDEP, Provincia de Buenos Aires, Argentina 2023/08/10 (17:00-18:30)
Stories Of The Ocean, Women And A Sea Of Changes In Chile: A Tribute To Trevor Platt 1Vivian Montecino, 1Doris Olivan Poster Session 1 Navigators and expeditions, Father Ignacio Molina, Alexander von Humboldt, Charles Darwin, Claudio Gay and other naturalists and masters, contributed to the knowledge of the Chilean sea, inhabited by coastal fishermen and canoeists. The extended Pacific western coast of South America (PSO) affected by multi-decadal, inter-annual, annual, and intra-seasonal scales produces more fish per unit area than any other region in the world. The beginnings of the development of marine sciences, is framed by the founding of the Marine Biology Station of the University of Chile (Montemar, UCH), two decades before the establishment of the National Commission for Scientific and Technological Research (CONICYT) in 1969. Abroad, 47 men graduated between 1962-2000 and 24 women between 1979-2011 (In Chile the first men graduated in 1986 and the first woman in 1998). The military coup in 1973 produced intervention, exodus, and transformations that affected science development. Contemporary, as pioneers’ participants in oceanographic cruises, we experienced the impact of initiatives that created teamwork that have favoured multi, interdisciplinary and interinstitutional work, with the gradual integration of women (Projects of the Marine Sciences Committee 1987-88 (UCH), JGOFS, FONDAP-Humboldt and the Oceanographic Research Centre in the PSO (COPAS) in Concepción in 2002). We highlight Trevor Platt impact as a mentor of a new generation of pelagic oceanographers and a teacher in several international courses (1984-1997). Similar initiatives have strengthened marine biology undergraduate and postgraduate programs in oceanography at Chilean universities. It is promising that new international centres will focus on global change and biocultural conservation among other ecosocial problems 1Universidad de Valparaíso Chile, Chile 2023/08/09 (17:30-19:00)
Spatial and temporal variations in oceanographic observations from Indus Dela and Adjacent NE Arabian Sea 1Waqar Ahmed, 1Tariq Mahmood, 1Samina Kidwai Poster Session 2 Spatiotemporal variation of physicochemical factors from the Indus Delta and adjacent NE Arabian Sea are of great importance in coastal ecosystems and in the regional and global oceanography. To Investigate the time series observations, Indus Deltaic Creeks (Waddi Khuddi (WK), Dabbo Creek (DC), and Khobar Creek (KC)) and adjacent offshore (Manora, Gadani, and Sonmiani bay) were sampled from October 2021 to August 2022 during the monsoons and intermonsoons. The effect of climate change and anthropogenic influences on the variations of oceanographic observations (Air Temperature (°C), Water Temperature (°C), pH, Dissolved oxygen (mg L-1), Chlorophyll a, (µg L-1), Nutrients , , and )( µM) will be presented. There were seasonal variation in the spatial averages of salinity, pH, TSM, and DO; creeks salinity varied seasonally as well at different stations. The lowest salinity (9.8) was observed from KC (the main Indus River channel) depending upon the monsoonal runoff and highest salinity was 36.6 from Sonmiani station, which is the western part of Pakistan Coast. The freshwater input from the river and seawater from the coastal sea toward the creeks during high tides play an important role in the distribution of living organisms. The water temperature ranged from 17.6 to 28.7 (°C). The chlorophyll a ranged from 0.8 to 2.6 µg L-1 with high concentration from KC. High concentration (11.6 µM) among the creeks stations was from WK might be due to the high density of mangroves and among adjacent offshore stations. Elevated concentration of was recorded from Manora station (near Karachi Port) due to the high anthropogenic influence. The decreased trend of concentration was observed from the creeks to adjacent offshore stations. Nutrient enrichment and eutrophication in coastal waters were mainly caused by urbanization and population increase, which affect the higher trophic level productivity and fish abundance in the coastal and shelf areas. Therefore, an integrated approach for the management and monitoring of upstream river and coastal systems is required for a better future 1National Institute Of Oceqanography, Pakistan 2023/08/10 (17:00-18:30)
Coupling ecological concepts with an ocean-colour model: Parametrisation and forward modelling 1Xuerong Sun, 1Robert J.W. Brewin Oral Session 3: Marine Optics & Ocean Colour Understanding how phytoplankton are responding to climate change is a major question in ocean science, and satellite remote sensing of ocean colour is our only means of monitoring phytoplankton in the surface ocean at high temporal and large spatial scales. However, developing ocean-colour algorithms for climate change studies requires addressing issues of ambiguity in the ocean-colour signal. For example, for the same chlorophyll-a concentration (Chl-a) of phytoplankton, the colour of the ocean can be different depending on the type of phytoplankton present. One route to tackle the issue of ambiguity is by enriching the ocean-colour data with information on sea surface temperature (SST). Here, we present an Ocean Colour Modelling Framework (OCMF) that incorporates three phytoplankton size classes (PSCs, pico-, nano- and microplankton) and assumes the presence of a background of non-algal particles in the ocean. The Chl-a of PSCs are derived from our recently developed ecological model, first proposed by Sathyendranath, S., ... & Platt, T. (2001) for two size fractions and now updated to three size classes with model parameters modulated by SST. In the OCMF, we assign chlorophyll-specific inherent optical properties (IOPs) to each class, include spectrally-independent parameters for non-algal and dissolved substances, and account for Raman scattering. The OCMF is parametrised and validated with a global in-situ dataset of IOPs, apparent optical properties, Chl-a, and SST. The OCMF will be used to help address questions on how phytoplankton are responding to climate change, as part of a UKRI Future Leader Fellowship. 1University of Exeter, UK 2023/08/10 (09:45-10:00)
Utilizing Satellite-Derived Bathymetry of turbid water coral reefs to improve hydrodynamic models of Southern Singapore 1Yochi Okta Andrawina, 1Felix Raque 1 Picar, 2Deha Agus Umarhadi, 1Kyle Morgan Oral Session 3: Marine Optics & Ocean Colour Satellite-derived bathymetry (SDB) data is becoming increasingly used as an input parameter in hydrodynamic models to comprehend coastal hydrodynamics. The spatial extent and resolution of the input bathymetry is critical for accurate modelled data outputs, especially within topologically complex coastal environments. High-resolution bathymetry data to improve modelling results could be achieved by applying SDB method in shallow water areas. However, application of this method in urbanized coastal regions, like Singapore, is challenging because the water depth data is obscured due to cloud cover in satellite data and elevated ocean water turbidity. Obtaining accurate bathymetry values from satellite data is difficult. Here we constructed SDB from Sentinel 2 satellite imagery using Stumpf algorithm from different tools extraction methods. First we utilized the Sen2Coral tools available in the Sentinel Application Platform (SNAP), and second, we built SDB from a long time dataset tool using Google Earth Engine (GEE) to minimise the effect of cloud cover and improve spatial data coverage. The SDB result derived from Sentinel 2A data accurately reflects only the shallow coral area within Singapore's turbid water region (to estimated depth of 20 m). Using both Stumpf algorithms in the GEE and the Sen2Coral SNAP, the best training and validation accuracy values were R2= 0.97 and 0.96, respectively. RMSE was greater for the GEE (2.53 m) than the Sen2Coral SNAP (RMSE = 1.71 m). Consequently, each pixel in the SDB can aid in understanding the surface morphology of coral reefs within the area, and each pixel of coral reefs Southern Singapore area could serve as a baseline input for the MIKE DHI hydrodynamics model. 1 Earth Observatory of Singapore; Asian School of Environment, Nanyang Technology University Singapore; 2Center for Remote Sensing and Integrated Surveys, Gadjah Mada University Indonesia 2023/08/10 (10:15-10:30)
Working with Trevor 1Žarko Kovač, 2Shubha Sathyendranath Oral Session 1: Physical and biological interactions A chronological overview of the past decade in primary production modelling is provided from a theoretical standpoint. The basic structure of biooptical primary production models is presented starting from the mathematical formulation of the photosynthesis irradiance function to the calculation of water column production. Theorethical advances in the form of new analytical solutions are given. New results on stability analysis using dynamical systems theory are highlighted and mathematical definitions of resilience, marginal production, anti/fragility and elasticity of primary production are presented. Conservation principles and the biooptical feedback are liked together in a new framework. The unification of critical depth, critical light and critical turbulence hypotheses is explored. 1University of Split, Croatia; 2Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, United Kingdom 2023/08/09 (11:00-11:30)
Capturing the seasonal to decadal variations of primary production from satellite ocean color measurements 1Zhongping Lee, 2Jinghui Wu, 2Joaquim Goes, 2Helga do R Gomes, 1Shaoling Shang, 3Jianwei Wei, 1Luping Song Oral Session 2: Marine Optics & Ocean Colour One of the primary goals of ocean color remote sensing is to provide synoptic estimates of phytoplankton primary production (PP) of the global oceans, which can then be utilized to characterize and understand variability of oceans’ biological-driven carbon cycle from episodic climatic events or long-term climate change. Over the past several decades, several algorithms have been developed to estimate PP from ocean color measurements, but many fall short of accurately capturing the spatial and temporal variations of carbon fixation. In this study, using decades-long PP measurements from three sites (oceanic sites HOT and BATS and coastal site CARIACO) and PP derived from satellite ocean color data, we demonstrate that when PP is estimated using phytoplankton absorption coefficients instead of phytoplankton biomass (or carbon), remotely derived PP agrees well with the magnitude of in situ measurements as well as captures the seasonal to decadal variations. These results suggest that using the phytoplankton absorption coefficient to estimate global oceanic PP from remotely sensed ocean color is a promising approach, but a complete exploitation of the method will require better spatial and temporal coverage of the quantum yield of phytoplankton photosynthesis, to provide better parameterization of absorption-based PP models. 1College of Earth and Ocean Sciences, Xiamen University, Xiamen, China; 2Lamont Doherty Earth Observatory at Columbia University, NY, USA; 3NOAA/NESDIS Center for Satellite Applications and Research, College Park, MD, USA 2023/08/09 (14:30-14:45)
Characteristics of subsurface chlorophyll maxima during boreal summer in the South China Sea with respect to environmental properties 1,2Guifen Wang, 1,2Wenlong Xu, 1,2Long Jiang, 1,2Xuhua Cheng, 3Wen Zhou, 3Wenxi Cao Poster Session 1 The South China Sea (SCS) is a semi-closed marginal sea in the western Pacific Ocean. Strongly influenced by the Asian monsoon, diverse physical- and biological dynamics in SCS could result in large spatio- and temporal variability of phytoplankton on both the horizontal and vertical scales. Characterizing the vertical distribution of chlorophyll a is crucial for accurate assessment of depth-integrated phytoplankton biomass as well as the primary productivity. In this study, the characteristics of the subsurface chlorophyll maximum (SCM) in the South China Sea (SCS) during the boreal summer were investigated by using bio-optical and hydrological data collected during four cruises from 2008 to 2015. During the boreal summer, a well-developed SCM layer was found to be a prominent feature in the SCS, with the thickness, depth, and magnitude of the SCM exhibiting large spatial variability. The vertical position of the SCM varied between 11 and 99 m, with an average value of 53 m. Light attenuation played a fundamental role in determining the depth (ZSCM) and magnitude of the SCM(Chlmax), as reflected by their relationships with the euphotic zone depth (Zeu). Significant positive correlations were found between ZSCM and the depth of potential density at 23 kg m−3 (Zσ=23), reflecting the importance of physical processes in modulating the fluctuation of ZSCM, especially in open-ocean areas. Anticyclonic eddies, which act to deepen the nutricline by means of isopyncnal displacement, may play a role in aggravating nutrient limitation in the SCM layer, which leads to deepening of ZSCM, weakening of Chlmax, and a fall in the total integrated chlorophyll a within the euphotic layer (ChlintZeu). Knowledge of ocean physical conditions and the variability of ZSCM should be taken into consideration to improve the accuracy of ChlintZeu estimates based on the surface chlorophyll a concentration (Chlsurf), especially when Chlsurf is very low. Our assessment of SCM parameters provides the basis for a better understanding and quantification of their role in primary production estimation within the SCS. 1 Key Laboratory of Marine Hazards Forecasting, Ministry of Natural Resources, Hohai University, Nanjing 210098, China; 2College of Oceanography, Hohai University, Nanjing 210098, China; 3State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China 2023/08/09 (17:30-19:00)