T3-6
Coral reefs are sanctuaries for a large portion of our planet’s biodiversity, but their rapid decline begs critical questions about what exactly is being lost, what are the driving forces that determine decline or resilience, and what are the implications for life on Earth. To address these questions, we synthesize the state of knowledge on the diversity of coral reef life forms at different scales of biological and ecological organization, encompassing variability in genes, biomolecules, cells, organs, organisms, populations, communities, ecosystems, socio-ecosystems, and biogeoclimatic systems, with a particular focus on French tropical overseas. We discuss research pathways to address knowledge gaps in various scientific disciplines, covering genetics (genomics, transcriptomics, proteomics, metabolomics), morphology, ethology, bio-acoustics, demography, functional ecology, macro-ecology, landscape ecology, human and social sciences, bioclimatology, and their cross-disciplinary interactions. Based on contributions from a team of coral reef experts working in coral reef regions spread around the world, our synthesis supports a better understanding of the various dimensions of coral reef biodiversity and proposes future research orientations for improving our knowledge of nature and its preservation. Given the rapid decline of coral reefs, and how much is still unknown, this work underscores the urgency of cross-scale biodiversity investigations for a systemic understanding of the drivers of biodiversity distribution and dynamics.
How to cite: Pellerin, F. and the Pellerin et al.: Snapshots of coral reef biodiversity and challenges in a time of crisis, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-272, https://doi.org/10.5194/oos2025-272, 2025.
Caribbean coral reefs, particularly those in the Florida Keys, are experiencing significant degradation driven by anthropogenic stressors. The most prominent of these is the phase-shift from coral-dominated to macroalgae-dominated ecosystems. These ecosystems are shaped by complex ecological interactions among reef organisms, with community composition varying between day and night. Many reef species exhibit different behaviors or become cryptic at night, leading to biases in traditional visual surveys and incomplete biodiversity assessments.
Environmental DNA (eDNA) has emerged as a transformative tool for biodiversity monitoring. This non-invasive molecular technique captures genetic material (e.g., skin cells, mucus) shed by organisms into their environment, enabling the detection of species presence and the identification of cryptic or elusive species that traditional survey methods might miss. While eDNA has been successfully applied in terrestrial and freshwater ecosystems, its use in marine environments, particularly coral reefs, remains an evolving field.
This study represents a novel application of eDNA to explore temporal variations in biodiversity on coral reefs, focusing on differences between diurnal and nocturnal periods in the Florida Keys. The primary objectives of this research are: (1) to investigate potential differences in eDNA profiles between day and night sampling, and (2) to complement traditional visual surveys with genetic data, potentially uncovering hidden species that might otherwise be overlooked. Water samples were collected from 13 reefs across the northern Florida Keys, using a Smith-Root eDNA backpack sampler, during both daylight and nighttime. Samples were filtered through self-preserving filters and analyzed by Jonah Ventures for DNA extraction and sequencing. Three genetic markers (16S, 18S, and COI) were used to characterize biodiversity across samples.
This study is innovative in its approach to understanding the full extent of biodiversity on coral reefs by integrating both temporal and genetic dimensions. The comparison of eDNA profiles between day and night sampling periods not only highlights the limitations of current eDNA practices but also underscores the necessity of accounting for temporal biodiversity shifts in monitoring efforts. By facilitating biodiversity assessments during nocturnal periods—when many species are most active—our approach aims to enhance the accuracy and completeness of biodiversity data. Furthermore, by generating genetic data from a broad spectrum of species, including those that are nocturnal or cryptic, this study will contribute to expanding eDNA reference libraries. A more comprehensive reference library enables more accurate species identification, which is essential for improving the reliability and scope of future eDNA studies across diverse marine ecosystems. This is critical for more effective conservation and management of vulnerable coral reef ecosystems.
Incorporating eDNA into coral reef monitoring offers a holistic, less invasive, view of species diversity and ecosystem health, providing insights that can inform restoration efforts and conservation strategies. By addressing the often-overlooked nocturnal component of reef biodiversity, this work contributes to a more nuanced understanding of ecosystem dynamics. Ultimately, this research will help refine eDNA methodology in marine environments and guide more targeted conservation and management practices for the coral reefs of the Florida Keys, and similar ecosystems globally.
How to cite: Williams, M. and Bracken-Grissom, H.: Uncovering the Secrets of Coral Reef Biodiversity: Using Environmental DNA (eDNA) to Assess Diurnal and Nocturnal Shifts in the Florida Keys, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1554, https://doi.org/10.5194/oos2025-1554, 2025.
Black corals are one of the ancient marine organisms in the mesophotic ecosystems, associated with the rocky reefs and barely known in Central America. Belonging to the Antipatharia order, Myriopathes panamensis and Antipathes galapagensis are two of the three known species in the Pacific coast of Costa Rica. These two where recently reported at a depth range of 15-45 meters and taxonomically described in the Gulf of Cuajiniquil, Guanacaste, a place that has a particular ocean condition related to the influence of the Thermal Dome of Costa Rica and lots of fisher communities who use the ecosystem services that these environmental bioengineers offer. In Costa Rica there are a few studies about the black corals, and little is known about the ecological importance of these species in the ecological dynamic. This study aims to assess the associated fauna of black coral reef ecosystems in the Gulf of Santa Elena and Playa Blanca Bay, Guanacaste. It provides a baseline understanding of the complex biological interactions surrounding black coral colonies, serving as valuable input for conserving the ecological integrity of these habitats.
The ecological status and macrofauna associated with various coral colonies were evaluated through SCUBA visual surveys and photography. During the assessment, every colony within a 30-meter transect was measured and examined for the presence of vertebrates and invertebrates utilizing the black coral as shelter or for other purposes. Additionally, the general substrate characteristics of the area were documented using a remotely operated vehicle (ROV) and GoPro footage to capture a comprehensive view of the habitat. Our findings reveal that black corals serve as vital nurseries for reef-associated bony fishes, including families such as Apogonidae, Cirrhitidae, Lutjanidae, and Serranidae. These species frequently rely on coral colonies for refuge and feeding. Among the invertebrate fauna, the most representative groups were Ascidiacea, Mollusca, Ophiuroidea, and Porifera, several of which were consistently associated with both species of black coral observed.
These results highlight the critical ecological role that black corals play in the Gulf of Cuajiniquil and Playa Blanca Bay. To safeguard these ecosystems, it is imperative to expand research efforts to better understand the impacts of fisheries, organism extraction, and climate change on these habitats.
How to cite: Medina de Lemos, D., Ulate Naranjo, K., Breedy, O., García Rojas, A., and Arias Zumbado, F.: Ecological health status of black coral reefs (Myriopathes panamensis & Antipathes galapagensis) in the North Pacific of Costa Rica, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-602, https://doi.org/10.5194/oos2025-602, 2025.
Rising ocean temperatures and marine heat waves associated with climate change cause mass coral bleaching and mortality, leading to population collapse and putting in peril many marine and terrestrial life forms that depend on tropical reefs, including human societies. Reef-building corals are particularly vulnerable to warming temperatures since they have relatively narrow thermal tolerances and often live close to their upper thermal limits. However, thermal conditions in which corals can survive and thrive, and tolerance to thermal stress, differ across species, and often within the same species, due to evolutionary, physiological, and ecological mechanisms. Limited knowledge on species thermal preferences and critical temperature thresholds prevents anticipating where and when coral populations may collapse as temperatures keep rising, which would enable responding with targeted conservation measures. We use a unique ~40 year-long archipelago-scale coral reef monitoring and sea surface temperature dataset to quantify thermal preferences and thresholds of major coral taxa using the broad reef system of New Caledonia representing ~6% of the world’s coral reef habitats. Our analyses quantify upper and lower thermal limits of major coral taxa, identifying species most vulnerable to a warmer future environment and requiring urgent conservation measures, and those more resistant and resilient. Our study facilitates targeted conservation measures for effective biodiversity conservation and coastal adaptation to climate change.
How to cite: Moysan, L. and the Moysan et al.: Assessing coral thermal preferences and vulnerability to climate change for targeted conservation, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-270, https://doi.org/10.5194/oos2025-270, 2025.
Long-term ecological monitoring is indispensable to identify and document changes from the triple planetary crisis of climate change, pollution and biodiversity loss. Coral reefs are some of the most biodiverse and most threatened of the Earth’s ecosystems. Accurate information on the status and trends of coral reefs equips decision makers with fundamental information to support the protection of these vital marine ecosystems.
Monitoring of coral reefs is conducted for many purposes, at various temporal resolutions and geographic scales, using various sampling techniques and indicators. The Global Coral Reef Monitoring Network (GCRMN), an operational network of the International Coral Reef Initiative (ICRI), has been producing high-level coral reef status and trend assessments since 1998. The most recent Status of Coral Reefs of the World report, published in 2021, estimated long-term trends of two widely collected indicators for the condition of coral reefs, hard coral cover and cover of macroalgae (both are recommended indicators of healthy coral reefs by ICRI, and ‘Essential Ocean Variables’ as defined by the Global Ocean Observing System). The global dataset spanned from 1978 to 2019 and showed that in most regions of the world, coral cover decreased while algal cover increased, indicating a widespread decline in the condition of coral reefs. The production of the next Status of Coral Reefs of the World report and of status reports from the Pacific and Caribbean regions is currently underway, and an overview of key findings will be presented.
It is challenging to combine disparate coral reef monitoring data for regional and global-scale assessments because of differences in sampling methods, sample sizes, lack of data standards and biases or gaps in the representativeness across geographic and temporal scales or for certain indicators. Notwithstanding these challenges, the value of regular quantitative analyses of such integrated datasets is immense. Ecosystem trends detected at regional and global scales provide a powerful basis to foster collaborative partnerships between scientists, conservation managers and practitioners, to understand key drivers and ecological dynamics for guiding and supporting evidence-based policies, and to equip Governments with essential mechanisms to implement and monitor their progress towards national and international targets and commitments.
The collective experience, capability and willingness to share knowledge and data under the umbrella of the GCRMN has also provided important learnings to facilitate more standardisation and interoperability of coral reef monitoring protocols, use of new technologies, improved data management and analysis, and capability-building of the next generation of coral reef monitors. This presentation will highlight some of these developments and how the GCRMN contributes to SDG14 by leveraging innovative tools and technologies and providing actionable knowledge on coral reef status and trends at different scales and to different audiences.
How to cite: Schaffelke, B., Brigdale, A., Dallison, T., Koss, J., McField, M., Petit, A., Planes, S., Rocle, N., Staub, F., Towle, E., and Wicquart, J.: The status and trends of coral reefs around the world – connecting science to conservation action, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-938, https://doi.org/10.5194/oos2025-938, 2025.
Coral reefs are exceptionally biodiverse ecosystems and their integrity is paramount for coastal societies. Nevertheless, coral reefs experience significant local and global anthropogenic pressures, and provide a sensitive indicator of coastal ocean health and climate change. Reef monitoring programmes have therefore become a standard tool to track changes within these ecosystems and are essential to better inform science, management and policy.
Aldabra Atoll UNESCO World Heritage Site in Seychelles, one of the world's most secluded ecoregions and among the largest atolls globally, has remained largely untouched by humans due to its remote location, limited freshwater resources, and challenging access. This makes it a unique and invaluable site for studying evolutionary and ecological processes on islands, and offers the opportunity to study the impacts of climate change on coral reef ecosystems in the absence of substantial local human pressure.
The Seychelles Islands Foundation (SIF), management authority of the atoll, has conducted annual monitoring of Aldabra’s coral reefs since 2014, capturing valuable long-term data on reef trajectories and resilience. This monitoring program has documented changes in coral assemblages through mass bleaching events, including the third global bleaching event in 2016 and the fourth global bleaching event in 2024, providing critical insights into the resilience and recovery potential of Aldabra’s reefs.
This presentation will outline the findings of this annual monitoring programme, highlight associated research initiatives into Aldabra’s reef resilience, and will provide first insights into the impact of the 2024 global coral bleaching event on Aldabra’s reefs. By sharing these insights, this presentation aims to deepen understanding of coral resilience mechanisms in a remote reef system. Aldabra’s reefs serve as a natural laboratory, offering valuable benchmarks for coral health in the face of climate change and contributing critical knowledge with the potential to support coral conservation strategies worldwide.
How to cite: Koester, A., Burt, A. J., Bunbury, N., Buckland, V., and Fleischer-Dogley, F.: Insights into coral reef resilience: monitoring and research at remote Aldabra Atoll, Seychelles, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-511, https://doi.org/10.5194/oos2025-511, 2025.
Monitoring coastal marine ecosystems associated with Marine Protected Areas is a tool that allows decision makers to have a real assessment of management effectiveness. With this perspective, rocky reefs have been monitored inside and outside Marine Protected Areas in the North Pacific of Costa Rica to determine, through the biodiversity of macroinvertebrates and vertebrates, the effectiveness and conservation of the marine trophic structures of these ecosystems. At a biogeographic level, the project data show a good state of health of the MPAs with more restrictive management measures, where a community of piscivorous predatory organisms is observed that keeps the lower trophic levels balanced, unlike the other MPAs, in which there is a predominance of prey organisms. It was observed that the most restrictive management categories have a lower variation between sampling periods, while the most lax categories, such as national wildlife refuges, showed the greatest variation between biodiversity indicators, evidencing the conservation effect that correct and effective management can have in marine protected areas.
How to cite: García-Rojas, A., Ulate-Naranjo, K., Arias-Zumbado, F., and Vega-Bolaños, H.: Are Marine Protected Areas really a conservation tool for marine biodiversity?: A case study in rocky reefs in the North Pacific of Costa RicaMonitoring, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-658, https://doi.org/10.5194/oos2025-658, 2025.
Climate-driven changes in marine ecosystem structure and function adversely impact the biodiversity and sustainability of living marine resources, food security, and the resilience of coastal communities. Understanding how climate change impacts marine ecosystem biodiversity and global fisheries, i.e. the ‘climate-biodiversity-fisheries nexus’, is a fundamental element of the UN Decade of Ocean Science for Sustainable Development. Several Ocean Decade-endorsed Programmes within the climate-biodiversity-fisheries nexus are building global networks to transform our capacity to understand, forecast, manage, and adapt to climate-driven changes in ocean ecosystems, including sustaining blue food resources that provide essential food security and nutrition in a rapidly changing world. Here we compare the scope, objectives, global partnerships, and capacities of these and other Programmes to facilitate effective collaboration and identify critical gaps in developing solutions to climate-driven changes in marine food webs, species assemblages and global fisheries. We will provide recommendations for new and existing Ocean Decade Actions around the climate-biodiversity-fisheries nexus to ensure the Ocean Decade can achieve the desired outcomes of a ‘productive, predicted, healthy and resilient ocean’ by 2030.
How to cite: Bograd, S. J., Anderson, L. C., Canonico, G., Chiba, S., Di Lorenzo, E., Enterline, C., Gorecki, E., Griffis, R., Kleisner, K. M., Lachance, H., Leinen, M., Mills, K. E., Müller-Karger, F., Roskar, G., Schmidt, J., Seary, R., Seeyave, S., Shau Hwai, T., Soares, J., and Tigchelaar, M.: Advancing the Climate-Biodiversity-Fisheries Nexus in the UN Decade of Ocean Science for Sustainable Development, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-679, https://doi.org/10.5194/oos2025-679, 2025.
Tropical coastal marine ecosystems, such as coral reefs, mangroves, and seagrass beds, harbor a significant portion of marine biodiversity and productivity, providing essential ecosystem services to human societies, including food and fisheries resources. However, global changes are causing rapid degradation of these ecosystems, resulting in the loss of ecological functions, habitats, and resources, which threaten both ecosystems and human societies. Successful examples of localized ecosystem and resource management exist, but generalizing these at larger, country and regional scales, which are relevant to strategic decisions, remains challenging. Identifying appropriate management measures is often difficult because ecosystem resilience is driven by various ecological processes that can be disrupted by a multitude of environmental stressors, including local pressures from fishing, habitat degradation and destruction, and global climate change, whose prevalence can vary across sites and species. We use a country-scale collaborative science approach to quantify long-term changes in fish communities, assess the efficiency of current management, and identify critical stress thresholds for sustainable management in the broad and biodiverse coastal system of New Caledonia. Our analyses characterize the distribution, composition, and abundance-biomass trajectories of key fish communities at various scales around the archipelago to shed light on local management successes and failures, as well as the mechanisms underlying resilience, to advise management decisions. Carried out in close collaboration with local communities, this work contributes to the development of sustainable management and conservation plans for New Caledonia’s exceptional coastal marine ecosystems and fish resources, which are listed as a UNESCO World Heritage site.
How to cite: Maggioni, F., Kulbicki, M., Guillemot, N., Albouy, F., Bertaud, A., Heintz, T., Letourneur, Y., Purkis, S., Dempsey, A., Roman, W., and Kayal, M.: Country scale assessments of coastal fish communities and drivers for sustainable socio-ecosystem management, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-292, https://doi.org/10.5194/oos2025-292, 2025.
The northeastern Brazilian continental shelf harbors diverse demersal fish communities that play essential roles in local fisheries and ecosystem functions. This study investigates taxonomic and functional β-diversity across depth and substrate types, analysing data from 62 trawling stations (from 5° to 9° S) and over 7,000 specimens representing 127 species. We computed β-diversity indices, specifically species turnover and nestedness measures, to examine how community composition varies with environmental and spatial gradients. Our results indicate that species turnover is the primary driver of taxonomic β-diversity, with distinct changes in species composition across stations. In contrast, functional β-diversity was generally high, with turnover and nestedness contributing equally. However, for functional β-diversity based on abundance data, overall diversity was low, suggesting that while functional composition differs between stations, the relative abundances of these species remain similar. Substratum complexity, depth, and particle dispersion gradients significantly influence β-diversity, supporting taxonomic and functional diversity in this region and maintaining essential functions such as resilience in nutrient cycling and energy flow. Integrating β-diversity metrics into Marine Spatial Planning (MSP) enables more effective targeting of habitats crucial to ecosystem function and resilience. Depth-stratified protection zones, for example, could benefit functionally diverse yet vulnerable habitats, particularly in deeper areas at risk of species and trait loss. Such MSP strategies align conservation and sustainable resource use, safeguarding the ecological roles and biodiversity of demersal fish communities on the northeastern Brazilian shelf.
How to cite: Aparecido, K., Merigot, B., Nole Eduardo, L., Bertrand, A., Reis, J., Duarte, P., Tosetto, E., and Fredou, T.: Ecological Drivers of Taxonomic and Functional Beta Diversity in Demersal Fish Communities of Northeastern Brazil: Implications for Marine Spatial Planning, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-492, https://doi.org/10.5194/oos2025-492, 2025.
Fish community biodiversity is gravely threatened by overfishing, habitat destruction, and climate change. These pressures impact fish stocks, which are economically, culturally, and ecologically essential. To ensure the conservation of fish communities, it is crucial to collect accurate data through regular monitoring programs. Currently, fish assemblages is primarily assessed through conventional methods such as underwater visual censuses (UVC), underwater video, and experimental fishing. UVC, which involves counting fish during dives, is the most commonly used method, yet it has limitations related to visibility, depth, and the detection of cryptic or pelagic species and requires taxonomic expertise.
Metabarcoding of environmental DNA (eDNA), derived from DNA fragments released by fish into the environment, emerges as a promising complementary method. By analyzing water samples, it is possible to identify present species without direct observation. Our recent study conducted in protected Mediterranean marine areas showed that eDNA surpassed UVC in detection capabilities, allowing for the identification of rare species often invisible through traditional methods (https://doi.org/10.1016/j.scitotenv.2024.177250). Furthermore, eDNA is not limited by depth or visibility, which facilitates its use in diverse conditions.
The assessment of fish biodiversity traditionally relies on taxonomic diversity (TD), which quantifies species and their abundance. However, functional diversity (FD), which measures the ecological roles of species, is increasingly considered a more relevant indicator for assessing the impact of anthropogenic disturbances. eDNA not only allows for species identification but also helps deduce their functional characteristics, such as dietary habits and social behavior. This information is valuable in understanding the impact of environmental changes on marine ecosystem functioning.
Nevertheless, eDNA presents certain limitations: it does not yet permit precise estimation of fish biomass or population density, and the transport of DNA molecules by currents can complicate the accurate identification of species' locations. UVC remains more reliable for these estimations. Additionally, some species detected by UVC evade eDNA detection due to the absence of their sequences in genetic databases.
Combining UVC and eDNA would provide a more comprehensive view of fish biodiversity. Further research is needed to optimize this mixed approach, which represents an opportunity to enhance marine ecosystem management. eDNA could also facilitate the early detection of invasive species coming from the Red Sea such as the lionfish, as well as the location of rare or endangered species like the angel shark, thereby supporting conservation efforts.
In conclusion, eDNA is an innovative method that, when combined with traditional techniques, could significantly enrich knowledge and support the conservation of marine ecosystems.
How to cite: Dérijard, B., Sabourault, C., Roblet, S., Gambini, G., Priouzeau, F., Marty, J., and Cottallorda, J.-M.: Environmental DNA to Enhance Fish Biodiversity Assessment., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-654, https://doi.org/10.5194/oos2025-654, 2025.
The 2024 Mesoamerican Reef Health Report Card evaluated 286 sites, noting an improvement in the Reef Health Index (RHI) from 2.3 (2021) to 2.5 (2023), out of a possible 5. However, 62% of sites remain in poor or critical condition, with only 10% rated good or very good. Regionally, coral cover and herbivorous fish biomass ranked ‘fair,’ while fleshy macroalgae and commercial fish biomass ranked ‘poor,’. Herbivorous fish biomass increased from 1,843g/100m² to 2,419g/100m² (2021-23), with notable gains in Belize and Guatemala. Commercial fish biomass remained stable except in Belize, which saw an increase from 330g/100m² to 791g/100m² (2021-2023). Coral cover decreased from 19% to 17%, primarily due to disease and bleaching. All reefs were exposed to severe heat stress, with approximately 40% of corals experiencing severe bleaching during 2023. However, most coral mortality occurred after the monitoring season, as in the iconic Banco Cordelia, Roatan, Honduras which went from 46% live coral in September 2023 to 5% in February 2024.
Higher grouper and snapper biomass is found within the Fully Protected Zones (FPZs), where all types of fishing is prohibited. FPZs cover only 3% of the MAR’s territorial seas and 11% of its coral reefs. Thus, there is great potential to improve reef health by expanding the area in full protection within the much larger Marine Protected Areas (MPA) areas already designated. There are >50 MPAs covering 57% of the territorial seas within the MAR. Well-managed and enforced MPAs are crucial for replenishing fish populations, particularly those with additional regulations like parrotfish and surgeonfish, which are protected in most of the MAR; and Nassau groupers, which are the only fin fish species with size limits and a closed season across the MAR. The Nassau grouper was the only species of grouper to have a relatively balanced size distribution with 44% of the fish surveyed meeting the minimum reproductive size, although total numbers are still very low. Integrating FPZs in ecologically critical areas, including Fish Spawning Aggregation sites and areas believed to be less prone to heat stress events, is vital for the maintenance of ecological structure and function and the large ecosystem scale of the Mesoamerican Reef.
Increasing the area in full protection to 20% has been a recommendation since our first Report Card was issued in 2008. Increases have been small and incremental compared to the pace and scale of the additional stressors. Improving sewage treatment and land use management in watersheds and coastal areas has also been a recurring recommendation for decades, with many versions of plans produced but few examples of effective implementation of these plans. Finally, without urgent and almost impossible reductions in greenhouse gasses, the escalating heat stress will soon overwhelm the adaptive capacity of coral reefs that continue to be stressed by anthropogenic stressors identified over thirty years ago. Our two decades of collaborative science-based monitoring and reporting has described way to assist coral reef survival, but it cannot implement the needed political actions, which may require a different novel approach.
How to cite: McField, M. M. and Muniz, I.: 2024 Mesoamerican Reef Health Report Card Records Improvement Despite Growing Challenges, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1536, https://doi.org/10.5194/oos2025-1536, 2025.
Coastal ecosystems are affected by numerous direct anthropogenic pressures (urbanization, fisheries, etc.) and global changes (climate change, biological invasions, etc.). Long-term monitoring of their biodiversity is crucial for (1) diagnosing disturbances as early as possible, (2) evaluating conservation (Marine Protected Areas) and restoration actions, and (3) better predicting the dynamics of their functioning. However, national and international programs are often limited in time (1-4 years) and offer few opportunities for standardized long-term monitoring in partnership with local stakeholders. To address this gap, French organizations, including the UMR Marbec and CEFE research labs, the Agence de l’Eau Rhône Méditerranée Corse, and the companies Spygen and EDF have collaborated to set up the ‘Sentinel Marine Areas’ network as part of the VigiLife international initiative. Since 2023, 13 Sentinel Marine Areas (SMA) distributed across the different maritime fronts of mainland France (Mediterranean, Atlantic, and English Channel) have been monitored annually using eDNA metabarcoding technology to identify the fish and crustacean species present. This non-destructive, highly efficient monitoring technology is ideal for assessing coastal biodiversity. Each SMA is centered on an area of interest (marine reserve, wind farm, thermal discharge from a nuclear power plant, artificial reef, entry point for non-native species), and several water filtrations are carried out by boat both inside and outside this area of interest. Each transect is conducted over 30 minutes during which 30L of seawater are collected and filtered 1m below the surface, sometimes complemented by filtration in the mesophotic zone (30-150m depth). Samples are then sent to the laboratory and processed using a standardized bioinformatic workflow to obtain a list of the species present. The objectives of this monitoring and research program are (i) to assess the influence of each area of interest on coastal biodiversity and its evolution over time, and (ii) to establish a network of sentinel sites to monitor the effects of climate change and the arrival of new species, as well as the effects of direct human pressures. During the first campaign in 2023, DNA copies of more than 140 fish species and 200 crustacean taxa were detected. These initial results have helped to update certain distribution ranges, with some species, such as the salema porgy Sarpa salpa, detected more than 500 km north of their former known northern limit. In connection with these northward shifts, we have also identified unprecedented species co-occurrences, the consequences of which on the functioning of coastal ecosystems are still unknown. The ‘Sentinel Marine Areas’ network is intended to become a permanent monitoring program, in particular by making local partners autonomous in carrying out the sampling, and to be extended to other areas of interest in France, including overseas, as well as to other territories abroad.
How to cite: Maire, A., Velez, L., Avouac, A., and Mouillot, D.: Long-term monitoring of coastal biodiversity in France using environmental DNA metabarcoding: the ‘Sentinel Marine Areas’ network, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1089, https://doi.org/10.5194/oos2025-1089, 2025.
Over the years, innovative methods based on EO-data (both aerial and satellite images) have been developed to increase the knowledge about coastal ecosystems, and stressors affecting them.
Managers of marine protected areas have been proactive; thanks to their appetence for EO-based technologies, they have provided a major contribution through the years enabling the emergence and acceptation of these new solutions.
Now there is a range of mature existing EO-based products for the monitoring and evaluation of both nature-driven (like turbidity, coastal erosion) and anthropogenic stressors (e.g. aquaculture, anchoring, dredging and other marine pollution) and of their interactions with marine ecosystems, in particular seagrasses.
This communication proposes to review how Earth Observation solutions powered by Artificial Intelligence have become main assets for the evaluation and reporting of marine policies (WFD, MSFD, FFHD / Natura 2000) and the management of Marine Protected Areas.
This will be featured by taking a few examples of several real case studies in french MPAs along the Atlantic and Mediterranean coasts. We acknowledge that these activities have been undertaken in the framework of projects and contracts with the French Biodiversity Agency (OFB) and in collaboration with the French Geological Survey (BRGM).
How to cite: Dehouck, A., Lafon, V., Beguet, B., Budin, R., and Regniers, O.: Satellite remote sensing, a central toolbox for the monitoring and evaluation of natural and human-induced stressors in relation with coastal ecosystems. Feedbacks from French Marine Protected Areas., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1087, https://doi.org/10.5194/oos2025-1087, 2025.
Marine forests encompass a wide range of ecosystems, from macroalgal beds to seagrass meadows and coral reefs. They play critical roles in shaping both population and community dynamics of the biodiversity they support. However, due to several threats such as overgrazing, the introduction of non-indigenous species and climate change, marine forests at a considerable risk of decline. Their capacity to recover is under enormous strain with many solutions, whether temporary or permanent, forced to be explored in the realms of restoration. As an integral component of the NIS-RECOV project, we present preliminary results, performed in the framework of European projects (i.e. FORESCUE) on the potential for natural recovery of Cystoseira forests in the shallow coastal waters of the Mediterranean. We draw on a fundamental law observed in both plant and coral populations referred to as self-thinning, where density-dependent mortality drives individuals to compete, leading to natural reductions in density as an ecosystem matures. This concept suggests that marine forests, such as those formed by Cystoseira, may undergo similar self-regulating development that reduces density, potentially enhancing resource availability for surviving individuals. Through the application of self-thinning principles, we seek to understand if natural recovery patterns of Cystoseira forests align with these dynamics. As observed in other vulnerable ecosystems such as coral reefs, self-thinning can aid recovery, suggesting that this law may be somewhat universal for sessile, habitat forming organisms. We seek to determine whether self-thinning operates across diverse ecosystems and to understand the implications for forest structure. The insights from this research would offer valuable guidance for conservation and restoration efforts by informing strategies that harness natural recovery mechanisms rather than relying solely on artificial interventions. This approach has the potential to foster a more resilient Cystoseira forest in the face of environmental stressors and provide a foundation for sustainable management practices that prioritize ecosystem stability.
How to cite: Mulla, A., Raybaud, V., and Mangialajo, L.: Roots of marine forest recovery, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-441, https://doi.org/10.5194/oos2025-441, 2025.
Shallow coastal ecosystems offer rich habitats for marine life, providing feeding, breeding, and sheltering grounds for numerous species, including crabs, mollusks, and juvenile fish. In response to beach erosion at Cape of Agde, a nature-inspired solution called PEGASE has been deployed as an alternative to traditional breakwaters. PEGASE structures, designed to biomimic mangrove forests, are placed on a sandy seabed flanked by two large quays with small breakwaters. Beyond its primary function of erosion control, PEGASE has demonstrated a remarkably positive impact on biodiversity.
After three years, the structures are fully colonized by mollusks, crustaceans, and macroalgae. Species such as oysters, mussels, barnacles, and dictyota algae attract various fish, predominantly sea breams and cryptic species like gobies and blennies, as well as crabs. PEGASE seems to offer suitable habitats for both juvenile and adult fish, including gilt-head seabreams.
Additional nighttime observations reveal that up to one octopus per structure, along with diurnal fish seeking shelter, frequent PEGASE. This rapid colonization and high abundance of mobile species have created a vibrant environment with increased macrofauna diversity compared to the surrounding sandy seabed.
The project demonstrates that PEGASE can serve as a viable alternative to breakwaters, fostering habitats for coastal marine macrofauna and flora. A joint abstract outlines PEGASE's design approach and its effectiveness in coastal protection. This study suggests that biomimicry, often requiring less material and offering aesthetic benefits, presents a compelling alternative to conventional methods for enhancing biodiversity. For coastal protection, such solutions can simultaneously support erosion control and biodiversity enhancement.
Keywords: Biomimicry, erosion, PEGASE, artificial reef, biodiversity, field monitoring, ecodesign, mangrove
How to cite: Lapinski, M., Charlemaine, J., Schubert, C., Ray, G., Martinot, M., and Dalle, J.: Erosion Control through Mangrove Biomimicry: Creating Ecologically Functional Artificial Reefs to Enhance Biodiversity, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1292, https://doi.org/10.5194/oos2025-1292, 2025.
Seagrass meadows are one of the most widespread and productive ecosystems in the coastal and estuarine waters worldwide. They trap and stabilize bottom sediment as ecosystem engineer, reducing the water currents through their physical structure that facilitate benthic faunal diversity and offer habitat for resident and transient fauna. Despite these ecological functions, this ecosystem has been suffering in the Bangladesh coast due to coastal morphological changes that are influenced by the monsoonal climate. This study aims to investigate the seasonal changes in seagrass density and biomass along with sediment erosional and depositional rates at seagrass vegetated dynamic estuarine sites, located in the south-eastern coast of Bangladesh. Additionally, this study made an extensive survey to record the benthic faunal assemblages and their spatial variation at four different seagrass sampling sites (i.e. St1 – St4). Moreover, water parameters and sediment characteristics were measured and compared among sites to understand their role in community assemblages. The results indicated that shoot density and biomass of the seagrass, Halophila beccarii showed monthly variation, which ranged 109–3143 shoots m-2 and 0.38–13.21g DW m-2 respectively. The shoot density rapidly increased after the end of monsoon (i.e. June–August) and reached maximum (3143±362 shoots m-2) in October. It also showed sharp decrease during dry winter months (i.e. November–February) due to sedimentation. Sediment deposition began during the post-monsoon (i.e. October–November), when the sea state conditions were relatively calm and continued until February. By the end of the winter (i.e. February) sediment accumulation reached maximum levels (11.31±1.56 cm) compared to October. Seagrass was absent for the period between February–June in the investigated sites as a result of unstable coastal morphology. Water temperature, salinity and conductivity ranged 28.5–29.6 ºC, 20.3–21.2 ppt, and 34.87–36.75 mS cm-1 respectively, which were not significantly varied among the stations. On the other hands, turbidity (10.3–20.2 NTU), total particulate matter (17.5–87.4 mg l-1), pH (7.81–8.23), dissolved oxygen (4.67–5.36 mg l-1), chlorophyll-a (1.9–7.3µg l-1), nitrate (5.92–28.47 mg l-1), and phosphate (0.37–3.98 mg l-1) contents in the water varied significantly in four sampling stations. Soil pH were found significantly lower (pH, 5.44±0.31) in the St2 than other stations (pH, 5.79–6.08) as a result of high organic carbon content (3.46±0.22%) therein. Moreover there was no significant difference in soil salinity (21.04–23.28 ppt) and texture composition (i.e. percentages of sand, silt, and clay) among those four sampling stations. However, the benthic sediment core sampling yielded a total of 6 polychaete species, 4 bivalve species, 7 gastropod species, 5 crustaceans and 2 other invertebrate species including sea cucumber and sea anemones. nMDS analysis for seagrass habitats explained 98% (R2 = 0.98) of observed variation in the data on benthic sediment macrofauna, which also indicated that abundances (i.e. shoot density) of seagrass and soil organic contents positively influences the benthic macrofaunal communities in the sampling stations. Considering the natural dynamics of the seagrass ecosystem, this study formulated conservation strategies involving coastal communities.
Key words: Monsoon, Halophila beccarii, sedimentation, benthic macroauna, seagrass conservation
How to cite: Chowdhury, A. B. and Chowdhury, M. S. N.: Performances of Seagrass meadows in monsoon dominated dynamic coast of Bangladesh, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-652, https://doi.org/10.5194/oos2025-652, 2025.
Mangroves, seagrasses, and coral reefs provide ecosystem services for three billion people worldwide. Studying these ecosystems is essential for their effective management. With the financial support of the French Embassy in the Dominican Republic, FUNDEMAR leads the MONITOREA program with the technical support of TNC and the Ministry of the Environment. The project created the national capacities and developed a manual based on recognized Caribbean protocols, allowing multiple actors to monitor the health of these ecosystems in space and time. The goal is to detect significant ecosystem changes and design policies for their conservation. During the implementation of the monitoring program, we have already detected that small losses in coral cover (2.6%) result in major losses in reef structural complexity (50-70%). The project also includes extensive national monitoring and intensive training to ensure local capacity and promote awareness about the value of these ecosystems. Here, we present the results of the 1rst national monitoring in Dominican Republic, which will contribute to existing monitoring networks in the region.
How to cite: Sellares Blasco, R., Croquer, A., Guendulain-Garcia, S. D., Villalpando, M. F., Valdez-Trinidad, A., L. Zubillaga, A., Zambrano, S., and Evangelista-Perez, D. Y.: MONITOREA: A roadmap for monitoring mangroves, seagrasses, and coral reefs and its first implementation in the Dominican Republic , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1432, https://doi.org/10.5194/oos2025-1432, 2025.
The international consensus on the urgent necessity to act to protect a vulnerable environment and endangered biodiversity raises key challenges, including the need to improve and accelerate estimating carbon stocks and changes in coastal ecosystems on a global scale. Remote sensing methods, combined with ground truthing and modelling, are essential for addressing this challenge cost-effectively.
The ESA Coastal Blue Carbon project is an unprecedented effort to review, assess, and attempt to provide key elements for the sustainable management of Blue Carbon Ecosystems (BCEs) through diverse case studies. Over two years, a multidisciplinary consortium is investigating the mangrove, seagrass, and tidal salt marsh BCEs in France, Canada, Spain and French Guiana. The project aims to develop innovative tools and methods based on Earth Observation (EO) to estimate and monitor changes in carbon stocks, and brings together a community of end-users, to ensure the tools meet the operational needs, including:
- Conservation stakeholders aiming to enhance the impact of their actions.
- Decision-makers looking to integrate blue carbon into national carbon accounting and set ambitious mitigation targets.
- The financial sector seeking reliable blue carbon investment opportunities.
Our rationale is to capitalise on existing data and multi-scale resolution imagery to assess the potential for global replicability of the space-based methodologies from highly representative pilot regions of the main BCEs across three different continents. The project consists of two phases: the first focuses on developing and consolidating requirements to create new methods on test areas, while the second emphasizes upscaling demonstration, and impact assessment. We aim at producing maps of carbon storage estimates for three different years from 2015 to 2025, with a spatial resolution no coarser than 10m while ensuring active participation from Early Adopters.
The project has been submitted to be endorsed under the Global Ocean – Blue Carbon Programme of UNESCO Ocean Decade.
How to cite: Séchaud, A., Beguet, B., Tranchand-Besset, M., Lafon, V., Dehouck, A., Proisy, C., Catry, T., Blanchard, E., Pellatt, M., Kohfeld, K., Serrano, O., Mateo, M., Sévin, M.-A., Cook, T., Coan, P., Ca'zorzi, A., Dupuy, C., El-Jamaoui, I., Volto, N., and Lachaussée, N. and the ESA Coastal Blue Carbon consortium: ESA Coastal Blue Carbon project: Towards Earth-Observation-based solutions for coastal blue carbon monitoring, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1158, https://doi.org/10.5194/oos2025-1158, 2025.
In marine ecosystems, biodiversity, biological rhythms, and macrofaunal community behaviors are fundamental to assess the cumulative impact of environmental and human pressures but they remain understudied. Ecoacoustics offers a promising approach to fill these gaps: it analyzes biological (biophony), abiotic (geophony), and anthropogenic (anthrophony) sounds to provide high temporal-resolution insights. Marine forests (e.g., kelp, seagrass meadows) are essential habitats, that rank among the most productive and biodiversity-rich ecosystems and provide billions of dollars of essential ecosystem services to humanity. However, with less than 3% of ecoacoustics studies, they remain largely underrepresented. Despite the potential of ecoacoustics in acquiring information on the cryptic species of dense habitats, the biophonic component of European marine forests is currently poorly or not documented.
Here we describe the biogeography of fish acoustic communities of three different marine forests (kelp forest, zostera and posidonia seagrass meadow) at the European scale (Atlantic and Mediterranean coasts). During the European TREC expedition, continuous sound recordings were conducted over 48-72h at 17 sites across Europe.
Using a standardized sound classification method, this biogeographic study provides the first detailed description of fish acoustic communities in European marine forests. We analyzed the composition and parameters of acoustic communities (abundance, richness, biodiversity indices) and revealed inter-habitat, intra- and inter-site variability. Acoustic communities were significantly distinct between habitats, with greater site variability within Zostera meadows, compared to kelp forests, suggesting differences in connectivity in seagrass. Site characteristics and sampling periods were considered, and relationships between acoustic communities, taxonomic diversity, diel variation and environmental variables (e.g., light, temperature) were examined. Our findings offer an unprecedented large-scale view of fish acoustic community composition in underexplored European habitats. This work reveals that acoustic biodiversity can contribute to habitat biogeography and infer information on the invisible, hidden animal assemblages, their dynamics and responses to environmental changes.
How to cite: Etheve, M., Salbin, E., and Di Iorio, L.: Biogeography of fish sounds across Europe’s Atlantic and Mediterranean coasts, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-988, https://doi.org/10.5194/oos2025-988, 2025.
Assessing responses of species, assemblages and habitats to environmental pressures or management actions is often challenging, but essential to preserve marine ecosystems, their functions and associated services. Adjusting management practices based on impact assessment and climate scenarios is a central aspect for MPAs that requires approaches capable of capturing the dynamics of marine life and appraise responses and alterations.
Recording sounds in ecosystems allows to investigate ecological complexity from species to communities, and habitats over days and months. Furthermore, as sounds are linked to behaviours, variations in sound production reflect responses to environmental changes or human impacts.
Based on multiple eco-acoustic studies within Western Mediterranean MPAs over several years, we show how acoustic fish communities as well as the acoustic courtship behaviour of vulnerable fish species vary with protection measures and human impact. Multivariate analyses and linear models reveal that acoustic diversity and courtship behaviour not only reflect the effectiveness of protection measures (i.e., zonation), but are also negatively related to human presence and activities, as highlighted by a highly significant decrease in sound abundance and richness with increasing boat traffic and recreational diving. Moreover, the analyses of multi-year datasets on reproductive sites reveal temporal variations of courtship calls that reflect diel biorhythms but also seasonal fluctuations that are partly altered by human activities and environmental changes. Finally, we also illustrate that analysing temporal variations allows to identify peaks in courtship calling that can be used as a proxy to identify sensitive periods during which human activities such as recreational diving and vessel traffic can be dislocated or reduced. This kind of information supports the definition of sustainable and targeted management practices, aiming at protecting functional sites and biodiversity hotspots while maintaining socio-economic activities. This work clearly highlights that long-term eco-acoustic monitoring is essential in providing an integrative and dynamic view of coastal ecosystems and organism-environment relationships in the face of environmental changes, and in supporting adaptive management.
How to cite: Di Iorio, L., Campillo, L., Ethève, M., Panzalis, P., Lavarello, I., and Hartmann, V.: Soundscapes as Sentinels: Eco-acoustics to monitor and assess ecosystem responses to anthropogenic pressures in marine protected areas, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-811, https://doi.org/10.5194/oos2025-811, 2025.
The Water Framework Directive (WFD) is the primary legislative act for the protection of water quality in the European Union (EU). In the Republic of Ireland, the Marine Institute Winter Environmental Survey (WES) fulfils the monitoring requirements of the WFD in coastal and transitional waters and has collected substantial data since its inception in 2011.
As a component of the WES, benthic macroinvertebrate communities have been monitored throughout Ireland. These communities have a well-established relationship with overall ecological status, and therefore have been adopted as a Biological Quality Element throughout the EU under the WFD. Furthermore, several indices have been developed to quantify the status of macroinvertebrate communities, with the Infaunal Quality Index (IQI) being implemented within Irish waters.
Research has taken a novel approach in elucidating trends in the hitherto relatively unexplored benthic macroinvertebrate community dataset. These data have been analysed here to detect changes, both spatially and temporally, within benthic communities to answer the question of whether these communities change over space and time in response to potential pressures? Additionally, biotope maps indicating the extent of the communities’ present have been created utilizing the pan-European EUNIS habitat classification system.
All analyses were conducted in PRIMER 7 using appropriate multivariate techniques such as cluster analysis, nMDS, and PERMANOVA. ArcGIS Pro was utilised to construct a biotope map for each waterbody.
The benthic communities within two natural harbours were explored to elucidate the effects of space and time. Waterford Harbour, located in the south-east of Ireland within the Celtic Sea, is an industrialised water body that is subject to extensive fine sediment dredging. Cork Harbour, located in the south-west of Ireland within the Celtic Sea is also industrialised and is in addition, classified as a heavily modified water body under the WFD.
Space and time were revealed as being significant factors in PERMANOVA for both Waterford Harbour (Time: df = 3, pseudo-f = 3.1257, p(perm) = 0.003. Space: df = 9, pseudo-f = 1.6239, p(perm) = 0.001) and Cork Harbour (Time: df = 2, pseudo-f = 5.9486, p(perm) = 0.001. Space: df = 14, pseudo-f = 2.8402, p(perm) = 0.001). However, differences exist within the estimated components of variation for Waterford Harbour (Time = 298.93, Space = 221.26) and Cork Harbour (Time = 472.58, Space = 914.45). These results indicate that while the benthic communities in Waterford Harbour are changing more throughout time than space, potentially because of pressures, Cork Harbour demonstrates the inverse, with the observed changes being driven by the spatial factor, despite the presence of pressures. These results are in alignment with the moderate and good IQI statuses for Waterford Harbour and Cork Harbour respectively.
The results here will be used to inform future WFD monitoring activities including the early detection of certain waterbodies that require more frequent monitoring due to changes in benthic community status. Additionally, the biotope maps created for each waterbody have numerous applications including informing restoration and protection of habitats, or to advise marine spatial planning activities.
How to cite: Watters, C., Nash, R., O Beirn, F., and Kavanagh, F.: Using benthic communities as a proxy for water quality to elucidate the effects of space and time within two natural harbours , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-554, https://doi.org/10.5194/oos2025-554, 2025.
The Deepwater Horizon oil spill in 2010 was an unprecedented event, releasing approximately 3.2 million barrels of oil into the deep Gulf of Mexico (GOM) resulting in injury to over 770 square miles of deep benthic ecosystems, including deep sea corals and soft-sediment habitats. The Open Ocean Trustee Implementation Group selected four projects to help address the injury to these resources. One of these projects, the Mesophotic and Deep Benthic Communities Habitat Assessment and Evaluation project, will address critical information gaps in our understanding of how the ecosystem naturally functions and recovers to inform restoration efforts. As sources of biodiversity, sediment communities in particular, provide important ecosystem services including nutrient cycling, sediment stabilization, and carbon sequestration. Initial injury in sediment habitats was characterized by high concentrations of hydrocarbons and metals associated with low taxa diversity and high variability in macrofauna (>0.3mm) communities. Since 2022, multiple offshore missions have been conducted to assess sediment community dynamics and environmental drivers, which combined with earlier post-spill assessments from 2010-2017, provide a long-term dataset with which to assess recovery, and both interannual and decadal natural variability within the system. Elevated hydrocarbon concentrations have persisted near the wellhead through 2022 with high variability in community metrics within the impacted areas. Our results update known baselines and quantify temporal change and recovery trajectories to inform restoration and long-term monitoring activities in the GOM.
How to cite: Bourque, J., Demopoulos, A., Chaytor, J., and Montagna, P.: Assessment of recovery and restoration of deep benthic sediment habitats injured by the Deepwater Horizon oil spill, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1473, https://doi.org/10.5194/oos2025-1473, 2025.
Extreme Climate Events (ECEs) challenge our ability to predict how climate change will alter ecological communities. Many ECEs, such as Marine Heatwaves (MHWs), are discrete, pulse-like events against a background of warming climatological means. MHWs can ultimately result in lethal stress and mass mortality events of marine organisms. Variability in MHW extremeness (across parameters of magnitude, duration, and frequency) makes forecasting individual organism response, and by extension population and ecosystem-level responses, difficult. We developed a mechanistic framework for predicting individual mortality risk and resulting population dynamics attributable to thermal stress experienced during MHW events. This framework uses thermal tolerance landscapes and dynamic survival models to estimate probability of death within a population during a MHW event. Focusing on habitat-forming species, and in particular the eastern Oyster (Crassostrea virginica), we demonstrate that extended, low-magnitude MHW events can be more common and as impactful as short, extreme MHW events. Our physiological approach yields substantial improvements over statistical oceanographic models and standard physiological thresholds of stress for predicting in situ impacts of MHW events on critical ecosystem-forming marine species. MHWs have been attributed to population and ecosystem tipping, and our approach provides one potential mechanistic lens of understanding how the extremeness of MHWs resonate across ecological scales.
How to cite: Villeneuve, A. and White, E.: Forecasting the impacts of Marine Heatwaves on habitat-forming invertebrate species , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-740, https://doi.org/10.5194/oos2025-740, 2025.
The loss of herbivorous fish and coastal eutrophication are driving shifts from coral to algal dominated reefs. The macroalga Turbinaria ornata, in particular, is greatly expanding habitat usage in the French Polynesia and the South Pacific, achieving densities so abnormally high that, when dislodged by storms, they create large floating rafts of aggregating algae. Although algal rafts are a common and important ecosystem in regions like the Sargasso Sea, T. ornata rafts are an entirely new tropical ecosystem observed the last few decades and do not have the ecological and evolutionary history that Sargassum rafts possess. T. ornata rafts form in shallow lagoons before transiting to open ocean environments, and are covered in epibionts, potentially increasing connectivity among reef ecosystems. Epibionts can include an array of epiphytes, invertebrates, and other microscopic organisms. Of particular concern are ciguatoxic dinoflagellates (e.g. Gambierdiscus and Ostreopsis) and coral pathogens. With climate change increasing the intensity and frequency of storms, T. ornata rafts will likely become a common feature of South Pacific reef ecosystems, but their impact on these ecosystems remains unknown. As such, it is essential to understand how these novel algal ecosystems may facilitate the dispersal of harmful epibionts.
This temporal study documents how the epibiont community on T. ornata rafts may change over time and compares these communities to attached T. ornata that plague the reefs of the South Pacific, providing critical insights into the potential of algal rafts of facilitate novel ecological connectivity among tropical reef ecosystems. I simulated T. ornata rafts by collecting T. ornata attached to the benthos to create rafts in mesocosms (1.2 m diameter, 1 m tall) with continuous flow of unfiltered sea water. I employed DNA metabarcoding to examine community composition and monitor epibiont changes across the timepoints that I sampled in three-day intervals over 30 days. For DNA metabarcoding, I used a suite of primers to target multiple groups: D1R/305R for dinoflagellates; 16S for microbes; 18S for protists; and, CO1 for metazoans. Preliminary investigations using microscopy revealed ciguatoxic dinoflagellate densities change over time on T. ornata rafts, but in ways that are not clear. For example, Ostreopsis density sharply declines over time while the highly toxic Gambierdiscus increased in density as well as variation in its density. Additionally, metabarcoding preliminary results regarding the microbial community indicate significant differences in alpha (Kruskal−Wallis: p = 0.0197) and beta diversity (PERMANOVA: p = 0.02) between microbes on attached and rafting T. ornata. Given the proliferation of T. ornata and the floating habitats they create, it is critical to better understand the composition and temporal dynamics of their associated epibiont communities to elucidate how this novel dispersal pathway may facilitate transport of epibionts among coral reef ecosystems, with unknown ecological consequences.
How to cite: Flores, A. and Barber, P.: Epibiont Community Compositions on Floating Turbinaria Rafts, Novel Ecosystems in an Increasingly Stormy Anthropocene, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-803, https://doi.org/10.5194/oos2025-803, 2025.
The world's oceans are undergoing rapid changes due to climate change and other anthropogenic impacts, affecting marine species' distribution, abundance, and behavior. Traditional ecological monitoring methods struggle to keep pace with these transformations, especially in underwater habitats. Recently, computer vision techniques have emerged to enhance the efficiency of video and image-based underwater monitoring. These methods facilitate the detection and classification of objects in visual data, potentially streamlining the process of counting and classifying marine organisms. However, the adoption of computer vision in marine ecology has been slow, partly due to its inaccessibility to ecologists and the lack of easily adaptable tools for ecological monitoring.
This study investigates the application and validation of computer vision techniques for monitoring underwater pelagic macrofaunal diversity, using a case study from coastal British Columbia. Over 9000 hours of underwater video were collected from four sites over 18 months, using mounted cameras programmed to record five minutes of video every hour.
Due to the infrequency of organisms present in the videos and challenges with underwater visibility, we created a stepwise iterative screening process to sequentially refine video data and aid the image annotation process. This involved using unsupervised classifiers (e.g. ResNet-18) to assist in reducing the number of background (i.e. 'empty water') images shown to annotators. To address the scarcity of annotations for certain taxa, an ‘adjacency filter’ was employed to increase the number of annotated frames for rare species. A rigorous QAQC process ensured standardization and minimized inter-annotator bias. Finally, a supervised computer vision model (YOLOv8) was trained with approximately 240,000 annotations to assess the presence and abundance of marine species over 18 months in the area. This approach provided high-resolution temporal data on the diversity and abundance of pelagic fish and gelatinous zooplankton at these sites.
Here, we detail the process of employing these computer vision techniques for long-term underwater ecological monitoring, emphasizing accessibility for ecologists. A stepwise method for adapting computer vision techniques to achieve biodiversity monitoring objectives is presented, highlighting the strengths and limitations of our approach. We address our work in the context of the key barriers facing computer vision in underwater ecology, and provide tools for researchers seeking to incorporate AI in image or video-based marine research. Finally, we propose future directions for integrating these technologies into new and existing monitoring programs, and suggest priority areas for future research to advance the use of computer vision in underwater ecological monitoring.
How to cite: Rimmer, T., Macintosh, D., Bates, C., Branzan Albu, A., Zhang, T., and Juanes, F.: Applications of Computer Vision in Underwater Ecology: A Case Study from the Northeast Pacific, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-998, https://doi.org/10.5194/oos2025-998, 2025.
Land biomass provides about 60% of the EU’s renewable energy. Scenarios for meeting the EU’s objective of carbon neutrality by 2050 suggest that more will be needed which puts pressure on land resources for other priorities such as growing food and feed and protecting wilderness . Over the world 55% of the mass of global aquaculture production in marine waters is devoted to algae and 33% to shellfish. The European part of this production represents about 3% of the total, half of which for shellfish and half for fish. In that context, macroalgae represent a confidential production in comparison to other species representing about 0.01% of European aquaculture production. In this context, one question of the European commission is to know how to obtain more food and biomass from the oceans without impacting future generations of their benefits. To answer this questions the study presented here, commissioned by the European Commission (EC) to support the European Green Deal, provides important insight into how increasing low-trophic level aquaculture could be planned in the future to contribute to the blue economy under the EU’s Green Deal. It is a matter of balance between benefits and drawbacks, using mathematical modelling and optimization based on Copernicus model outputs of oceanic circulation and nutrients over European seas. For three seaweed and three shellfish species, maps of production potential in fresh and dry weight, Kcal and protein equivalent and CO2 and nutrients uptakes are provided. Moreover, maps of the optimal distribution of farms for different target production levels (2 to 10 MTons of fresh weight) and their impact on nutrients are also produced.
How to cite: Bryère, P., Johnson, M., Maguire, J., Jutard, Q., and Mangin, A.: Scaling-up EU cultivation of shellfish and algae for European Green Deal, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1298, https://doi.org/10.5194/oos2025-1298, 2025.
The Ocean Biomolecular Observing Network (OBON) is an international programme endorsed by the UN Decade of Ocean Science for Sustainable Development (“UN Ocean Decade”) and led by the Partnership for Observation of the Global Ocean (POGO) that aims to accelerate informed decision-making to restore the health of our ocean using the universal signatures of life on Earth: biomolecules. OBON acts as the strategic hub for a global biomolecular observatory in support of the UN Ocean Decade, bringing knowledge based on biomolecules and capacity to advance and broaden their application to diverse ocean users – for example, to monitor biodiversity and understand how it is changing in response to multiple stressors such as pollution, habitat loss, and climate change. OBON will also help communities detect biological hazards like harmful algal blooms and pathogens, and support the management of fisheries and Marine Protected Areas. To achieve this, biomolecular observations need to become a key component of next-generation ocean observing systems – the biological equivalent of the Argo network of profiling floats. To achieve our vision, we are working with our growing family of 20+ endorsed Projects to ensure that biomolecular observations of the ocean are globally coordinated, harmonised, Findable, Accessible, Interoperable and Reusable (FAIR), and reliably flow into the Global Ocean Observing System (GOOS) - via the Ocean Biodiversity Information System (OBIS)- as standard practice integral to sustainable ocean management. OBON’s core pillars are to (1) Innovate technology and methodologies, delivering frameworks to advance biomolecular observations from the coastal to the open ocean, thus enabling broad-scale interpretations and scientific discovery; (2) Develop resources, networks and strengthen capacity globally, to advance observations and analyses while ensuring equitable access to ocean knowledge and resources; and (3) Enhance the use and interpretation of these data through FAIR data practices and model integration, and the creation of ocean knowledge. Together, this work informs ocean users and managers, ensuring sustainable interactions in support of a healthy ocean. This presentation will provide an overview of the OBON programme, progress to date and recent developments, as well as ways for the global biomolecular observation community to engage. In particular, we will provide examples of OBON’s work on policy engagement (e.g. with the Convention on Biological Diversity and UN Framework Convention on Climate Change, UNFCCC), fisheries management, technology/instrumentation, and capacity development, which have been achieved through several workshops bringing together providers and end-users of biomolecular data and information.
How to cite: Seeyave, S., Leinen, M., Beckman, F., Pitz, K., Robidart, J., Rodriguez-Vargas, L. H., Tan, S. H., van de Kamp, J., and Wilson, W.: The Ocean Biomolecular Observing Network: A global hub for biomolecular measurement of marine life , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1128, https://doi.org/10.5194/oos2025-1128, 2025.
El Salvador is the smallest and most densely populated country in Central America, with access only to the Pacific Ocean slope. Along its 321 km of coastline, many local communities depend on coastal marine ecosystems and the resources and services they provide. These communities are at the same time the most vulnerable to climate change scenarios, unplanned coastal development, food security and gentrification. The Marine and Limnological Research Center works closely with coastal communities, including them in the process of generating scientific information as key actors in society, since it is recognized that their knowledge and experience is valuable in decision-making in the integrated management of ecosystems and marine governance. Thanks to the synergy between academia, government institutions, local coastal communities, private enterprise and international cooperation, in recent years we have generated important information for the declaration of new marine protected areas, the structuring of a fund for the financing of science for ecosystems such as reefs, the development of government tools for planning and management against pollution and marine debris, and the evaluation of vulnerable and endangered species. These efforts have also allowed us to increase biodiversity records in different taxa, the discovery of new ecosystems such as black coral forests, the monitoring of species that were thought to be extinct in the country and the generation of technical and scientific knowledge published in indexed journals and transformed into educational material to be used in schools. In addition to this, results have been shared with other countries in the region such as Guatemala, Honduras and Costa Rica, who have shown interest in establishing research projects under a collaborative line with a regional approach that integrates the socio-environmental realities of each country. For El Salvador, marine sciences have proven to be a valuable source of knowledge for decision-making based on data and evidence.
How to cite: Trejo, A. and Segovia, J.: El Salvador's coastline: A treasure worth preserving, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-930, https://doi.org/10.5194/oos2025-930, 2025.
Seamounts serve as crucial aggregation sites for pelagic species in remote environments, which are often vulnerable to unregulated fishing. However, the high costs and logistical challenges of reaching these remote locations usually limit long-term survey efforts. The biological importance of seamounts along the Cocos Ridge, between the Galapagos and Cocos Islands, for threatened migratory species has been previously acknowledged, though past studies have been limited to short-term, spatially restricted surveys. From 2021 to 2024, we expanded biological and oceanographic surveys at the West Cocos and Gemelas seamounts, the shallowest seamounts within the Cocos Island National Park, using baited remote underwater video stations (BRUVS) and a CTD instrument to measure environmental variables along the water column to a depth of 100 meters. A total of 276 BRUVS were deployed in two distinct zones around each seamount: at the seamount’s peak and 10 nautical miles away, under the hypothesis that pelagic species abundance and diversity would be significantly higher closer to the seamounts. Our analysis revealed significant differences between survey sites, with higher abundance and diversity of pelagic species observed near the seamounts. The hammerhead shark showed the strongest association with the seamounts, although its abundance was negatively correlated with higher water temperatures, deeper thermoclines, and lower oxygen levels in the water column. Both seamounts were identified as biologically important areas, not only for hammerhead sharks but also for thresher sharks and silky sharks—all endangered species that are highly exposed to fishing pressure in the Eastern Tropical Pacific (ETP). Our findings provide a crucial baseline for evaluating the effectiveness of the 2021 expansion of Cocos Island National Park and demonstrate that the aggregation effect of seamounts for large, threatened pelagic species is concentrated within small spatial scales around each seamount. Based on this study, a regional initiative to monitor seamounts has been promoted through the MigraMar network of scientists, paving the way to expand this effort across the ETP in the coming years.
How to cite: Cambra, M., Villalobos, F., Clarke, T., and Espinoza, M.: Seamount aggregation effects for threatened species at Cocos Island National Park: Insights from a Long-Term Monitoring Framework in the Eastern Tropical Pacific, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1550, https://doi.org/10.5194/oos2025-1550, 2025.
The identification of Important Shark and Ray Areas (ISRAs) represents a critical approach to supporting the conservation of vulnerable elasmobranch species globally. ISRAs are science-based designations for spatially significant habitats essential for the survival and recovery of various shark and ray populations. Their establishment relies on a rigorous set of criteria that assess ecological importance, such as the presence of essential life-history stages, critical migratory routes, and unique population assemblages. However, defining precise ISRAs for data-deficient, often pelagic and migratory, elasmobranch species is challenging. These include the Atlantic pygmy devil ray (Mobula hypostoma), a pan-Atlantic species for which data on population structure, habitat use, and seasonal movements remain limited.
In this presentation, we describe the criteria and methodological framework for identifying ISRAs applied to a poorly documented species, M. hypostoma, in the northern Gulf of Mexico. In this case study, various observational and analytical methods including citizen science sighting reports, acoustic and satellite telemetry, stable isotope ratios as biomarkers, species distribution modelling and population genomics are used to understand the spatiotemporal distribution of M. hypostoma in the study region, as well as the ecological value of the habitats (with regard to feeding, mating, birthing grounds, nurseries and migration corridors) frequented by the species. Our results indicate that M. hypostoma undertakes significant seasonal migrations – likely driven by seasonal prey availability – between West Central Florida and the northern Gulf. Upon reaching maturity, an ontogenetic shift occurs, with juveniles and subadults primarily feeding in shallow coastal waters while adults predominantly forage offshore in deeper waters, along the continental slope and in canyons, with dives reaching depths of up to 180 meters. The Emerald Coast in Florida appears to provide critical foraging habitat for juveniles and subadults (individuals less than 100 cm disc width), with some individuals residing in the area for up to six months annually.
Based on these findings, we propose two candidate ISRAs for M. hypostoma in the northern Gulf of Mexico: the Emerald Coast as a primary feeding ground, encompassing the shallow coastal waters and the head of the DeSoto Canyon; and the waters connecting this region to West Central Florida as a vital migration corridor. These preliminary areas of interest will be submitted to the Independent Review Pannel for evaluation during the North American and Caribbean Atlantic regional workshop (2025).
Our findings illustrate how rigorous biodiversity observation and monitoring efforts can enable scientists to identify and designate ISRAs. By generating actionable, data-driven insights, ISRAs offer decision-makers and stakeholders essential information for implementing targeted conservation measures within broader marine protected area networks. This approach exemplifies a pathway to more informed, equitable, and ecosystem-based conservation strategies that bridge science and policy for the benefit of marine biodiversity.
How to cite: Boggio-Pasqua, A., Bassos-Hull, K., Wikinson, K., DeGroot, B., Valek, J., Fogg, A., Ajemian, M., Nerini, D., and Ménard, F.: Important Shark and Ray Areas for pelagic, migratory data-deficient species: A case study of Mobula hypostoma in the northern Gulf of Mexico, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-326, https://doi.org/10.5194/oos2025-326, 2025.
Since 2006, the Te mana o te moana foundation has been monitoring a unique green sea turtle (Chelonia mydas) nesting site at Tetiaroa Atoll in French Polynesia. This presentation will highlight key findings from this long-term research and outline upcoming research initiatives.
Key results include:
- Nesting Monitoring: Over 7,500 turtle tracks have been recorded, with approximately 3,800 nests identified, and more than 350,000 eggshells counted.
- Female Identification and Tracking: Detailed profiles of over 360 females have been created, documenting their nesting frequency and migratory return routes through satellite tracking.
- Hatchling Predation and Rat Eradication: Crucial insights into local hatchling predation have been gained, especially in the context of rat eradication efforts.
- Beach Profile Changes and Erosion Threats: Changes in beach profiles due to erosion have impacted nesting sites, prompting the development of a re-vegetation project using indigenous plant species.
- Study of Sub-adult Green Turtles in Tetiaroa Lagoon: New research focuses on sub-adult green turtles using acoustic and LoRaWAN tags to better understand their behavior and habitat use in the lagoon.
This program is part of a larger, over 20-year study conducted by the French Polynesian government. The findings now contribute to seminars, training, and capacity-building efforts across other Polynesian islands, with a focus on sea turtle nesting inventories supported by a dedicated application developed by our teams of veterinarians and biologists.
How to cite: Gaspar, C.: 18-Years of green sea turtle monitoring on Tetiaroa atoll in French Polynesia: key results and paths to the future?, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-396, https://doi.org/10.5194/oos2025-396, 2025.
Long-term surveys provide essential data on ecosystems change, climate trends, and the impact of human activities on ecosystems. Collecting data consistently over extended periods prevents misleading or speculative interpretations linked with interannual variability and reveals shifts those short-term studies might overlook. The CRIOBE – SNO CORAIL conduct numerous monitoring programs in tropical islands in the South Pacific, some of which have been ongoing for more than 50 years. Constantly evolving since 1987, this monitoring covers a vast region, including French Polynesia (with 10 islands across different archipelagos) as well as several neighboring Polynesian island nations (Cook Islands, Kiribati, Pitcairn, Samoa, Tonga). Coral reefs are critical ecosystems for these countries as they provide protection against rising wave submergence in a context of global warming and play and essential role in the economy, both as a driver of tourism and as a primary income source for fisheries and aquaculture. Additionally, they are crucial for the global biodiversity, hosting 25% of all marine species. These surveys allow us to identify trends, helping in developing more accurate models and predictions essential for stakeholders to develop effective mitigation and adaptation strategies. Our findings revealed that coral reef demonstrate a notable level of resilience, with a capacity for regeneration within less than 10 years in the absence of additional stress. However, the increasing frequency in bleaching events along with the global increase of temperature, is inducing a shift in fish communities that could reduce this recovery capacity. Therefore, we need to implement solution that support coral reef recovery to maintain areas large enough and in sufficient health to enable recovery when environmental conditions improve.
How to cite: Chancerelle, Y., Sasal, P., Siu, G., and Planes, S.: Importance of long-term surveys to monitor ecosystems: the case study of coral reefs in the South Pacific, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1520, https://doi.org/10.5194/oos2025-1520, 2025.
Climate change affects the oceans directly (e.g., increase in salinity and temperature of surface waters) or indirectly (e.g., changes in precipitations and winds for example). Those modifications affect living organisms, especially plankton that, by definition, can not move when facing unfavorable conditions. For this reason, plankton is considered as a good sentinel of the global state of open sea ecosystems. In addition, plankton plays a key role in the functioning of marine ecosystems, as a main actor of the carbon cycle or as the base of food webs. Monitoring and understanding how planktonic communities respond to global changes is therefore a major priority at global scale, as evidenced by the recent "Plankton Manifesto" edited by the UN or plankton's status as an Essential Ocean Variable according to the Global Ocean Observing System.
In this context, long time series of plankton biodiversity observations are a key tool. In the Mediterranean Sea, considered as a global warming hotspot, the historical marine station of Villefranche-Sur-Mer continues to carry out one of the oldest zooplanktonic time series in the world. Starting in 1967, a 330 µm mesh sized net has been deployed bimonthly, all year round, between 75 m and the surface. Over 900 formalin-preserved samples were recently re-processed with a quantitative imagery device (the ZooScan) and the resulting 2M individual images processed through an artificial intelligence pipeline to provide individual measurements and taxonomic classifications.
From this data, we describe long term trends, seasonal changes, and regime shifts in the mesozooplanktonic community, in relation to environmental conditions (temperature, oxygen , chlorophyll a). And, since the images provide access to individual measurements, we can also explore changes in ecologically-relevant traits such as size, transparency, etc. Among other things, we show, together with significant warming and decrease of chlorophyll a concentration; changes in zooplankton concentrations and shifts in community composition. These changes also translate into significant changes in individual-level traits. Causal inference approaches indicate significant top-down control of zooplankton on phytoplankton, which seems to be increasing with time. Such extraordinarily long observations give us access to these long term, climate-scale processes and are therefore precious in our globally changing world.
How to cite: Laux, L. and Irisson, J.-O.: Long-term monitoring of zooplankton diversity in the Mediterranean Sea in a context of climate change over 55 years, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1074, https://doi.org/10.5194/oos2025-1074, 2025.
The livelihoods of more than 3 billion people depend on marine coastal socio-ecosystems. Yet, local anthropogenic stressors and global human-driven climate change increasingly threaten the sustainability and resilience of the tightly interdependent socio-economic and environmental systems. Long-term observation of coastal environments including biodiversity and associated socio-economic activities is absolutely critical for an holistic understanding of the functioning and dynamics of such socio-ecosystems, risk management, and for evaluating the relevance of public policies.
Despite significant progress in observation efforts over recent decades, particularly for physical, chemical and biogeochemical variables, sectorial fragmentation has precluded the development of the systemic-thinking and holistic analysis that is essential to fully understanding the complexity of coastal socio-ecosystems. Complementing traditional approaches, innovative technologies such as environmental genomics and in situ imaging for biodiversity monitoring, as well as the crowd-sourcing potential of social media for human activities, are leading to the implementation of more agile “augmented observatories”. The roll-out of this more socially responsive and integrative approach will lead to development of new indicators to track and understand the healthy functioning and change trajectories of coastal ecosystems, and will greatly facilitate the implementation of eco-responsible sustainable development initiatives designed to address major environmental issues.
In this context, the key-goal of the current FUTURE-OBS project (2022-2028) is to develop systems-thinking based targeted strategies for multi-scale and multidisciplinary observation of coastal socio-ecosystems in France. Work focus on environmentally sensitive areas, such as vulnerable maritime façades (English Channel and north-western Mediterranean Sea), marine protected areas and aquaculture zones, which act as demonstrators and use cases. The holistic socio-ecosystemic approach driven by FUTURE-OBS brings together scientific experts from distinct fields such as oceanography, ecology, economics and social sciences, along with public and private sector stakeholders, decision-makers and bodies representing citizens, to identify priorities and ensure a broader uptake of the solutions produced. The development and deployment of data-intensive approaches for observing biodiversity and societal uses produce a massive quantity of new and heterogeneous data which implies an in-depth strategic reflection on how best to structure, make accessible, and maintain new and existing data in-line with the FAIR principles. This conceptual design phase is essential to guarantee the optimal exploitation of multi-scale and multi-source marine data and serve as a basis for developing new thematic and integrated indicators. The routine use of interoperable, data-intensive approaches enable the introduction of new artificial intelligence tools and machine learning capabilities in the ocean observation. These new generation of augmented observatories can provide new data and insights for a sustainable management of coastal socio-ecosystems in the changing environments.
How to cite: Thiébaut, E., Not, F., Amice, G., Artigas, F., Cointet, J.-P., Desroy, N., Eveillard, D., Grémare, A., Hoebeke, M., Irisson, J.-O., Jeanthon, C., Le Bras, Y., Lescot, M., Lucas, R., Mongruel, R., Monchy, S., Mostajir, B., Vaz, S., and Vincent, D.: FUTURE-OBS : Developing a new generation of augmented observatories to ensure sustainable and equitable management of coastal socio-ecosystems, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-744, https://doi.org/10.5194/oos2025-744, 2025.
Posters on site | Poster area "La Baleine"
The Northeast Atlantic has been exposed to a wide range of direct human pressures, such as fishing, shipping, coastal development, pollution, and non-indigenous species (NIS) introductions, in addition to anthropogenically-driven global climate change. Nonetheless, this regional sea supports a high diversity of species and habitats, whose functioning provides a variety of ecosystem services. As part of the 2023 OSPAR Quality Status Report, here,for the first time, we use a semi-quantitative approach to evaluate holistically the state of Northeast Atlantic marine biodiversity across marine food webs, from plankton to top predators, via fish, pelagic and benthic habitats, including xeno-biodiversity. Our analysis reveals widespread degradation in marine ecosystems and biodiversity, which is likely the result of cumulative effects of multiple human activities, such as overexploitation, the introduction of NIS, and climate change. Bright spots are also revealed, such as recent signs of recovery in some fish communities and recovery in harbour and grey seal populations in some regions. The status of many indicators, however, could not be assessed due to gaps in data, unclear pressure-state relationships, and the non-linear influence of some pressures on biodiversity indicators. Lessons learned will drive progress towards a better integrated assessment of wide-scale marine ecosystems.
How to cite: McQuatters-Gollop, A., Guerin, L., Gilles, A., Holland, M., Lynam, C., Mitchell, I., Stebbing, P., Schukel, U., and Vina-Herbon, C.: Assessing the state of marine biodiversity in the Northeast Atlantic, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-15, https://doi.org/10.5194/oos2025-15, 2025.
Global change is causing redistribution of marine species worldwide, modifying fish population and stock structure, as well as community compositions. These changes may have strong impacts on marine fish, associated fisheries, and ecosystem functioning and services. However, our capacity to assess and monitor short and long-term changes in species distribution and biodiversity is hampered by data availability and heterogeneity around the globe. This presentation will introduce FISHGLOB, launched in 2019 and an UN Ocean Decade project since 2023, that has collected and combined a unique data set of scientific bottom trawl surveys (SBTS) conducted regularly during the last decades across the globe. SBTS are ecological observation programs that sample marine communities associated with the seafloor. These surveys report taxa occurrence, abundance and/or biomass in space and time, and they can contribute substantially to understanding responses of species and communities to global change. Because combining these data together remains challenging, FISHGLOB enhances access and visibility of SBTS around the world and integrates these data across regions through an international network of experts. Currently, the integrated FISHGLOB dataset encompasses public and private surveys. Metadata comprises over 280,000 samples (hauls) from the last two decades of 95 surveys performed across all continents. Biodiversity data covers more than 3,000 fish taxa collected since 1963 from 65 surveys. FISHGLOB biodiversity data is accessible on github.com and osf.io for the 26 surveys that are public. We are now growing the consortium as an international community of practice, maintaining the core FISHGLOB database, and using the database to address research questions about global change impacts on fishes – focusing on marine heatwaves, community turnover, species’ extinction risk, and more – at an unprecedented scale. None of this would have been possible without open and collaborative data science, which enabled our “big data” approach to studying and managing species and community changes. FISHGLOB sets the stage for a long-term international collaborative platform bringing together marine data and experts from data science, ecological research, government agencies, and management in order to support biodiversity and fishery management adaptation in a time of global change.
How to cite: Mérigot, B., Maureaud, A., Fredston, A., Guralnick, R., Kitchel, Z., Palacios-Abrantes, J., Pécuchet, L., Pinsky, M., Shackell, N., Thorson, J., Palomares, M. L. D., and consortium, T. F.: FISHGLOB: Fish biodiversity facing global change, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-39, https://doi.org/10.5194/oos2025-39, 2025.
As part of the Marine Ecosystem Restoration (MER) project, ISPRA plans to map coastal habitats along the entire Italian coast, an innovative initiative under the National Recovery and Resilience Plan (PNRR).
ISPRA has selected the Fugro-led consortium to use its cutting-edge technologies to map coastal environments, a revolutionary approach that is expected to transform marine ecosystem conservation and restoration efforts. The survey activities will be carried out along the entire Italian coastline and will include the mapping of Posidonia oceanica, Cymodocea nodosa and other major species of marine phanerogams native to the Mediterranean, integrating multi-scale technologies, including sensors operated from aerial platforms (topo-bathymetric LiDAR, RGB and hyperspectral camera and gravimeter), satellite sensors, surface sensors (multibeam type) and finally the use of autonomous underwater vehicles (AUV) for direct and high-resolution observation of coastal ecosystems.
Seagrass meadows are habitats of very high conservation value and are also extremely important because they are an incredible ally in the fight against climate change. They capture carbon up to 35 times faster than tropical rainforests and represent more than 10% of total ocean carbon storage while covering only 0.2% of the seabed. In addition, they provide protection and nutrition and are a habitat for other forms of marine life.
This ambitious and unprecedented extreme survey campaign across the entire Italian coastline will provide very high-resolution data. These data will improve the decision-making process of local administrations in terms of protection and restoration of marine habitats and species.
The mapping program of the MER project, unique in its kind in Europe, will provide Italian institutions, including the Ministry of the Environment and regional administrations, with high-resolution data on marine habitats. The project supports the European Biodiversity Strategy for 2030, with the goal of creating protected areas covering 30% of the EU’s terrestrial and marine surfaces. Special focus will be given to the mapping and monitoring of Marine Protected Areas and Natura 2000 Sites.
How to cite: Cajelot, B., Rende, S. F., Filippone, M., Tunesi, L., and Giorgi, G.: Integration of multi-scale technologies for the Italian coastal mapping and monitoring programme, with emphasis on Posidonia oceanica and Cymodocea nodosa meadows (MER project, PNRR), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-41, https://doi.org/10.5194/oos2025-41, 2025.
Remote sensing is key for monitoring marine wildlife, offering dynamic solutions for tracking populations like marine mammals. However, it often produces vast datasets that require extensive human effort to analyze. Automatic image analysis using deep learning has been explored, but models face challenges generalizing to new datasets with varying conditions. To address this, a human-in-the-loop approach combines AI with expert biologist input for high-quality analysis. This method was tested on aerial images of belugas in Nunavut, achieving over 90% agreement with expert annotations using only 100 manual inputs. It also saved 96% of the time compared to manual analysis, showing its potential for scaling wildlife monitoring.
How to cite: Charry Tissier, E.: Scaling marine mammals monitoring using AI: A human-in-the-loop solution to analyze aerial datasets, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-44, https://doi.org/10.5194/oos2025-44, 2025.
The Philippines, a global biodiversity hotspot, boasts a rich marine ecosystem encompassing estuaries, mangrove swamps, seagrass beds, coral reefs, and pelagic environments. However, these vital ecosystems face increasing threats from human activities and climate change. To address these challenges, effective monitoring and conservation strategies are urgently needed.
A significant barrier to marine conservation is the lack of comprehensive biodiversity knowledge. DNA metabarcoding, a cost-effective and versatile technique, is emerging as a powerful tool for assessing biodiversity.
This study represents the first attempt to employ DNA metabarcoding on towed plankton net samples to assess the biodiversity of two key ecosystems in Aklan, Philippines: Batan Estuary, characterized by mangroves and seagrass beds, and Tangalan Bay, known for its mangroves, seagrass beds, coral reefs, and pelagic environments. By analyzing the cytochrome oxidase I (COI) and 18S rRNA genes, we uncovered distinct species assemblages in each ecosystem. Mollusks dominated Batan Estuary, while cnidarians, reef fish, and other reef-associated organisms were prevalent in Tangalan Bay. Our findings reveal a high percentage of meroplankton, demonstrating the effectiveness of plankton net sampling in capturing diverse marine life.
How to cite: Payne, M. M. and Hirai, J.: Unveiling Marine Biodiversity in the Philippines through DNA Metabarcoding: A Contribution to Global Biodiversity Discovery and Inventory, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-51, https://doi.org/10.5194/oos2025-51, 2025.
Sundarbans Biosphere Reserve is a part of the Sundarbans mangrove forest and is currently facing several hydrological climate challenges. Two rivers, Matla and Thakuran, were extensively studied during the monsoon and post-mon season of 2019 and 2020. A time-series program, Sundarbans Biosphere Reserve Time Series (SBRTS), was established in 2019, to monitor seasonal trends along the Matla and Thakuran estuaries. SBRTS has 250 stations and was monitored over June 2019, November 2019, and November 2020 to map the hydrological conditions, including temperature, salinity, pH and dissolved nutrient concentrations. Phytoplankton abundance was mapped along these estuaries. Salinity, EC, TDS and pH showed distinct seasonal and spatial gradients. Phytoplankton communities showed strong site specificity and only Cyclotella was present in all stations at all sampling seasons as seen by SpAD analysis. The formation of microniche harbouring selective phytoplankton genera in high abundance appears to be controlled by environmental factors. However, the overall distribution of phytoplankton across the studied estuaries, resulting in microniche formation, may be controlled by localized water dispersal patterns. Understanding phytoplankton distribution patterns can provide key insights into niche partitioning in the Sundarbans Biosphere Reserve.
How to cite: Ghosh, A. and Bhadury, P.: Microniche selects phytoplankton community structure in the interconnecting creeks of the Indian Sundarbans, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-81, https://doi.org/10.5194/oos2025-81, 2025.
Global change, under the influence of increased anthropogenic disruption, presents one of the greatest challenges of the modern age. Estuaries are situated at the confluence of terrestrial and marine environments and are especially vulnerable to these pressures due to their proximity to land-based activities. These activities typically enhance anthropogenic nutrient enrichment of these ecosystems, culminating in accelerated rates of eutrophication. The heightened proliferation of invasive alien aquatic plants (IAAPs) is a common eutrophic response in the freshwater reaches of estuaries that highlights the escalating impact of human activities. This study investigates the significant threats IAAPs pose to the ecological integrity of estuaries by disrupting native biodiversity and altering ecosystem function. This therefore has implications for local fauna and flora as well as the socio-economic implications for communities reliant on these ecosystems. Focusing on the National Biodiversity Act as a framework for managing estuaries in South Africa, the study explores the mechanisms of invasion in various estuarine environments, emphasising the vulnerability of highly polluted estuaries and those that periodically close to the sea (temporarily closed estuaries). Estuaries known to support IAAPs in South Africa were investigated to assess the impacts that IAAPs pose to their ecological integrity. The distribution and density of IAAPs (i.e., Azolla filiculoides, Ceratophyllum demersum, Lemna gibba, Myriophyllum aquaticum, Pistia stratiotes, Pontederia crassipes and Salvinia molesta) in selected South African estuaries were quantified to understand their prevalence and spread. Moreover, the study explored the pathways and factors contributing to IAAP invasion in estuaries, including nutrient input from land-based activities and habitat alterations. This was achieved through field surveys, water quality analysis, and stakeholder engagement, allowing for a comprehensive assessment of the mechanisms of invasion and their potential ecological impacts. The study found that IAAPs are present in almost all estuary types in South Africa and are common along the subtropical east coast due to substantial wastewater inputs and the predominance of freshwater conditions which favour their growth. By synthesising the current scientific findings with actionable management strategies, this research aims to bridge the gap between science and policy, providing stakeholders with a roadmap to address the challenges posed by IAAPs. The findings will contribute to management efforts geared towards preventing and/or reversing the continued deterioration of water quality and spread of IAAPs in South African estuaries, as highlighted in the latest National Biodiversity Assessment. Investigations such as these are critical given that the persistence of invasive species is an indication of ecosystem deterioration and a loss of natural resilience. Thus, early detection of ecosystem health degradation enables more cost-effective and successful management interventions.
How to cite: Lakane, C., Lemley, D., and Adams, J.: Invasive alien aquatic plants in estuaries: From science to management, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-89, https://doi.org/10.5194/oos2025-89, 2025.
Sundarbans, the world’s largest continuous mangrove forest, an UNESCO World Heritage Site and a RAMSAR Site, formed at the Ganga Brahmaputra Meghna riverine system of the Bay of Bengal of Northern Indian Ocean, is home to a large population of mangrove horseshoe crab (Carcinoscorpius rotundicauda) , along with Indo Pacific horseshoe crab (Tachypleus gigas). In 2020, a category 5 very severe cyclonic storm ‘Amphan’ hit and badly affected population and habitat of mangrove horseshoe crabs acrossSunda rbans including Sagar Island. Immediately following cyclone, intense field work was initiated involving local communities to determine population status of mangrove horseshoe crab. The habitat assessment was undertaken by assessing status of mangrove vegetation, quantifying the nature of sediment grain size patterns, status of benthic biodiversity and using stable isotope based measurements. Besides, with the help of indigenous and local communities including fisherfolks, marine litter was removed systematically during the study period. Targeted attempts were undertaken to rescue and release mangrove horseshoe crab from other affected islands gradually into the restored habitat of Sagar Island through involvement of park managers. Immediately following cyclone, population status showed a sharp decline of 1-2 individuals per km (compared to 12-15 individuals per km) in Sagar Island and there was large scale destruction of habitat attributes including that of mangrove vegetation. The silty-clay nature of sediment (35-40% of texture proportions) was replaced by coarse and fine sand particles across habitats of mangrove horseshoe crab. Besides, marine litter dominated by plastics, ghost nets, among others were found across the habitats of mangrove horseshoe crab. More than 500 kgs of plastic and ghost nets were removed between June, 2020 and January, 2021 with the active involvement of local fisherfolk communities to restore the habitats of mangrove horseshoe crab. The sediment texture analysis revealed gradual transition to silt-clay nature of sediment. However, microplastic abundance in sediment and surrounding intertidal water column were found to be higher. During this period, there was occasional presence of adult mangrove horseshoe crabs; however juvenile forms were not encountered. From February, 2021 the occurrence of mangrove horseshoe crab showed an increase (3-5 individuals per km). The overall number of mangrove horseshoe crab presently shows an increasing trend and restoration activities led by coastal fisherfolk communities have led to population and habitat recovery of mangrove horseshoe crabs in Sundarbans through a nexus of science, society and policy.
How to cite: Bhadury, P.: Population and habitat recovery of mangrove horseshoe crab after a major cyclonic event in the coastal Northern Indian Ocean , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-99, https://doi.org/10.5194/oos2025-99, 2025.
The marine ecosystems of the Galapagos Marine Reserve (GMR) host unique biological communities, including some of the world’s most biodiverse coral reefs. However, global climate variability increasingly threatens these reefs, with the GMR experiencing similar degradation. Monitoring these vulnerable sites, especially during and after El Niño Southern Oscillation (ENSO) events, is essential for understanding how temperature shifts impact these ecosystems. Using DSLR cameras, overlapping images were captured across eight 10x10 m plots in key coral areas within the GMR, enabling the creation of photomosaic 3D models. Advanced techniques, such as Structure from Motion (SfM) for high-resolution 3D reef mapping and deep learning models for ecological analysis, segmentation, and plot registration, have been employed to facilitate temporal comparisons of coral health and coverage. This research offers an in-depth view of the GMR’s response to climate variability, underscoring the resilience and adaptability of its subtidal communities to environmental shifts. The findings provide the Galapagos National Park Directorate (GNPD) with critical insights to inform management strategies aimed at bolstering coral resilience against future climatic events.
How to cite: Keith, I., Teran, F., and Yuval, M.: Unveiling how climate variability shapes coral reefs in the Galapagos Marine Reserve, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-130, https://doi.org/10.5194/oos2025-130, 2025.
Fish larvae abundance is related to zooplankton composition and physicochemical properties in mangrove-seagrass seascapes of Zanzibar (Tanzania)
Barnabas Tarimo1, 2, Monika Winder1, Peter Thor3, Martin Gullström4*
1Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
2Institute of Marine Sciences, University of Dar es Salaam, Zanzibar, Tanzania
3Swedish University of Agricultural Sciences, Department of Aquatic Resources, Lysekil, Sweden
4School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden
*Corresponding Author E-mail: tarimobarnabas@yahoo.com
Abstract
Mangroves and seagrass meadows constitute essential habitats of the coastal seascape, particularly through their multifunctional role, including being important nursery grounds for many fish species. Nevertheless, there is scarcity of information about food-web dynamics and interaction and water physicochemical properties in association with fish larvae abundance and diversity in these seascapes. We investigated the influence of water physicochemical properties and abundances of zooplankton on fish larvae abundance and diversity. Fish larvae, water physicochemical variables (chlorophyll a concentration, temperature, salinity) and zooplankton were sampled monthly in three habitats: mangroves creeks, inshore and nearshore seagrass. These data were then used to model the influence of variations in water physicochemical parameters and different zooplankton taxa on fish larvae abundance and diversity using partial least squares (PLS) regression analysis. Our study found that salinity correlated negatively with fish larvae abundance and maintain the association throughout the seasons, sites and habitats, whereas water temperature showed a positive correlation with fish larvae abundance across space and time. In Chwaka Bay, seascape fish larval abundance exhibited a positive association with the abundance of selected zooplankton taxa, including copepods, gastropod larvae, bivalve larvae, and cirripedia larvae across the seasons. In Fumba, non-copepod zooplankton, namely bivalve, cirripedia, and gastropod larvae, and calanoid copepod abundances were negatively connected with the abundance of fish larvae throughout the habitats over the seasons. Our findings highlight the influence of salinity, temperature and chlorophyll a and zooplankton abundance on fish larvae abundance in mangrove-seagrass areas. The associations of salinity, temperature and chlorophyll a and zooplankton with fish larvae abundance and variations across the seascape differences are discussed.
Keywords: Fish larvae, seagrass, mangroves, zooplankton, chlorophyll a concentration, temperature, salinity
How to cite: Tarimo, B.: Fish larvae abundance is related to zooplankton composition and physicochemical properties in mangrove-seagrass seascapeass seascapes of Zanzibar (Tanzania), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-201, https://doi.org/10.5194/oos2025-201, 2025.
Title: SALT OF THE EARTH: A BIOFILM’S ABILITY TO WITHSTAND VARYING SALINITIES AND IMPLICATIONS FOR BARNACLE COLONIZATION
Authors: 1,2Laurynn Thompson Torres, 1Dr. Wei Xu, 1Dr. Ioana Emilia Pavel, 1Dr. Lin Zhang, 1Dr. Yajuan Lin, and 1Kyra Kaiser.
Affiliations: 1Texas A&M Corpus Christi, 2NOAA Coastal & Marine Sciences
Abstract:
Current climate conditions in the Western Gulf of Mexico are undergoing significant water chemistry changes. Salinity levels rapidly fluctuate with varying seasonal conditions, inducing consistent variability of abiotic stressors in the water column. Marine biofilms support the settlement of marine sessile organisms by colonizing non-living Crassostrea virginica shells. Due to the fluctuating salinity levels, marine biofilms may no longer accumulate satisfactory extracellular polymeric substance (EPS) components. Marine biofilms allow for the detection, exploration, and potential permanent settlement of local barnacle species such as Amphibalanus amphitrite. Marine biofilms must meet certain morphological, chemical and functional standards to entice barnacle cypris larvae to ‘explore’ the biofilm and permanently settle. These microbial communities are highly adapted to these conditions and respond to any deviations in the water chemistry including salinity. The salinity alterations present in marine biofilms can harm local barnacle colonization. Thus, the main goals of this project are (a) to identify potential alterations in the morphology, composition, and bacterial community of the marine biofilm under varying salinity levels (10, 25, 36, 50 ppt), and (b) to investigate the effects of biofilm alteration by salinity on the larval settlement of barnacles and physiological/behavioral responses of settled adult barnacles. These will be achieved using three well-established chemical and biological characterization techniques. (i) In our preliminary work, Raman spectroscopy has confirmed the establishment of marine biofilms on oyster shell substrates through characteristic biochemical vibrational modes. Furthermore, Raman analysis will chemically fingerprint the microbial community encased in the biofilm EPS matrix. Raman spectroscopy is a well-established analytical chemistry technique that has yet to be utilized in the studying of marine biofilm establishment on oyster substrates and its ecological connection to foundational coastal species. (ii) Compound Stable Isotope Analysis of Amino Acids of Nitrogen (CSIAA-N) will identify the nitrogen ratios and the metabolic pathways in the biofilm leading to microbial functional identification and insight into bacterial functional diversity of the biofilm community. (iii) DNA sequencing will provide additional details on the biofilm microbial population's taxonomical diversity and the overall community composition. The results emerging from these analyses indicate that marine biofilms will change in 3-D architecture, bacterial composition, and community diversity will increase under varying salinity conditions. These biofilm changes will cause different settlement rates of cypris larvae and physiological responses in the adult barnacle. Overall, this study will provide insight into how salinity will change the microscape of a biofilm and its assisting role in the establishment of healthy and productive coastlines.
How to cite: Torres, L.: Salt of the Earth: A Biofilm's Ability to Withstand Varying Salinities And Implications For Barnacle Colonization, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-271, https://doi.org/10.5194/oos2025-271, 2025.
Established in 2016, France’s National Research Infrastructure for Coastal Ocean and Littoral Observation (herein “ILICO”) is dedicated to understanding the dynamics of coastal and littoral systems at the triple interface of Continent-Ocean-Atmosphere in both France’s mainland and overseas territories. ILICO ensures the required long-term multidisciplinary observations of these complex environments from coastal dynamics (shoreline, sea level), biodiversity (phytoplankton, benthic macro-invertebrate communities), to physico-chemical composition. To address ecological and methodological challenges ILICO has adopted a holistic approach to (i) better understand the trajectories of these ecosystems subject to local, regional, and global (external) drivers, (ii) characterize both direct and indirect effects of pressures on environmental processes and ecological status, (iii) identify recurring, rare, and extreme events and their impacts, (iv) better predict their evolution in the short and long terms, and (v) disentangle the effects of anthropogenic impacts from natural pressures. ILICO’s nine certified National Observation Services (SNO) deploy an almost exhaustive set of measurement and analysis technologies within coastal ocean and littoral landscapes, covering a wide range of essential oceanic and biodiversity variables. It also comprises certified Community Code coupling physics, biogeochemistry, and biology in order to merge observations and modeling. The challenge of achieving “Integrated Observations” from multi-platform, multi-variable, and multi-scale sources requires ILICO’s collective skills and expertise to develop and optimize both methods and tools needed to sustainably manage these ecosystems. ILICO ensures the interoperability and quality of observations according to FAIR principles (also including discussions about IA-ready data for Digital Twin of the Ocean), through close collaboration with France’s e-infrastructure for environmental data DATA TERRA. The presentation with showcase examples that successfully merge ILICO time series from in situ approaches, modeling, and remote sensing for the study of coastal erosion and sea-level rise, biodiversity, toxic and/or harmful algal blooms, and recent heatwaves. The aims are (i) to present the scientific added value of a nationally structured Observation infrastructure within the European and international contexts; and (ii) to highlight how ILICO should provide knowledge for the protection and restoration of coastal environments to those involved in the management and decision-making processes in these environments, with a view to co-constructing the Observation of Tomorrow along the land-coast-ocean continuum at both national and European levels. Beyond its mission to provide Observation data for the scientific research community working on complex coastal ocean and littoral systems and for the Society, ILICO is also a key player (operator) to provide high-quality data to ensure necessary environmental assessments in-line with European directives and regional sea conventions.
How to cite: Lefebvre, A. and the RI ILICO consortium: Coastal and Littoral Environmental Observation in France: Towards an Integrated System Led by National Research Infrastructure ILICO., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-337, https://doi.org/10.5194/oos2025-337, 2025.
The Gulf of Nicoya is a tropical estuary located on the Pacific coast of Costa Rica. Changes in river inflow during dry and rainy seasons make the gulf a dynamic ecosystem. During the rainy season, freshwater input and organic matter discharge cause environmental gradients that affect the structure of the bacterioplankton communities so that at the beginning of the rainy season, the surface layers of the gulf are relatively homogeneous; the opposite occurs during the dry season, where is observed more significant heterogeneity in the structure of the bacterioplankton communities along the surface of the gulf. The determination of these changes in microbial diversity and abundance throughout the year are insights for understanding the dynamics of the ecosystem and establishing indicators for the development of mariculture projects, such as oyster farming.
How to cite: Marín-Vindas, C., Suárez Baldelomar, A., and Vega-Corrales, L.: The structure of bactrerioplankton in a tropical estuary, the case of the Gulf of Nicoya, Costa Rica., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-415, https://doi.org/10.5194/oos2025-415, 2025.
Species dispersal is more complex in the ocean than on land because most marine biota have early life stages that are passively transported by currents within the plankton. By being spawned and recruiting in distinct local communities, these drifting organisms interconnect distant marine systems into large metacommunities. Consequently, the origin of the organisms recruiting to a particular local community has great influence on its biodiversity. The strong circulation governing western boundary current systems poses challenges for species recruitment and the assembly of local communities. We have investigated and highlighted this through a series of high-resolution (1/36°) community-based Lagrangian dispersal modelling experiments conducted along the Tropical Southwestern Atlantic, which is part of the Atlantic Meridional Overturning Circulation (AMOC).
In western boundary current systems, the strong currents flowing along the coast are highly advective, and organisms spawned along the coast are rapidly transported away. Therefore, coastal and neritic species face a challenge in recruiting to the suitable habitats present along these systems. The western boundary currents also spread open ocean waters and their associated fauna over the continental shelf. The continuous arrival of allochthonous species, overlapping local retention, results in the mass-effect assembling archetype, leading to homogeneous local communities dominated by the best dispersers, excluding autochthonous species and, consequently, reducing local and regional biodiversity.Despite this dominant assembly pattern, stochastic and seasonal fluctuations around the western boundary current such as eddies, meanders and countercurrents, can create hotspots of autochthonous species retention. Specifically for the Tropical Southwestern Atlantic, these fluctuations are caused by the interaction of currents and topography and the seasonal variability of the intertropical convergence zone. At these hotspots, species in each local community are sorted according to their ecological niches and interactions with other autochthonous species (species sorting assembling archetype), resulting in heterogeneous local communities and higher regional biodiversity. Similarly, when islands and seamounts are present off western boundary current systems, as we observed along the Fernando de Noronha Ridge, strong epipelagic westward currents pose challenges to the retention and recruitment of organisms. Particularly if no other shallow water source systems is present to the east. However, we saw that the diel vertical migration allow organisms to reach depth strata with reduced current speeds or even undercurrents flowing in the opposite direction to the surface. This condition increases the retention of autochthonous species and the possibility for organisms spawned over the continental shelf to reach these offshore systems, either directly or through stepping-stones.The dispersal patterns observed in the Lagrangian experiments align with the few already known spatial patterns of biodiversity distribution along the Tropical Southwestern Atlantic and provide important insights for regions and taxa for which knowledge is limited or absent. These results also provide elements for the proper definition of biodiversity conservation and management strategies and for a better understanding of the processes regulating community assembly in highly advective systems around the globe.
How to cite: Giachini Tosetto, E., lett, C., Neumann-Leitão, S., and Bertrand, A.: Species dispersal and community assembly facing the Atlantic Meridional Overturning Circulation, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-510, https://doi.org/10.5194/oos2025-510, 2025.
The American blue crab (Callinectes sapidus), a species that has been reported sporadically in Europe for over a century, began proliferating in the Mediterranean in 2016, first in Spain (Ebro Delta), then in 2017 in France in the Canet-en-Roussillon lagoon (Pyrénées-Orientales) before spreading to a large part of the Mediterranean. Several areas in France (Etang de Berre, Corsica, etc.) and abroad (Italy, Croatia, etc.) are now under pressure from this species, which is destabilising coastal ecosystems and affecting fisheries.
To gain a better understanding of the reasons for this proliferation, in 2023 and 2024 we conducted a multifactorial study of the biology of this species, funded by the French government, the Occitanie Region and the Syndicat Mixte du Bassin Versant du Réart. The various factors studied were:
- characterisation of the life cycle of the blue crab by studying its larval development, determining its period of reproduction and recruitment of juveniles;
- estimating the blue crab's physiological tolerance to variations in temperature, salinity and oxygen concentration;
- characterisation of the food web using an isotopic approach and the analysis of digestive contents;
- inventory and potential impact of parasites and comparison with the native species (Carcinus aestuarii);
- assessment of the impact of the blue crab on the benthic communities of the étang de Canet.
The results presented will enable us to better anticipate the impact of the blue crab on the benthic communities of the pond.
How to cite: Hourdez, S., Desdevises, Y., Romans, P., Magnanou, E., Charles, F., Sarabeev, V., and Labrune, C.: Multifactorial study of the invasive blue crab (Callinectes sapidus) in the Canet-Saint-Nazaire lagoon (Pyrénées-Orientales), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-514, https://doi.org/10.5194/oos2025-514, 2025.
The ocean plays a crucial role in addressing some of the world’s most pressing challenges, including climate change, biodiversity loss, and food security. Recently, we’ve witnessed a significant increase in awareness of the ocean’s importance across governments and industries, as seen at major conferences like Climate COP29 and Biodiversity COP16.
While there are passionate conversations and promising collaborations underway, there’s an urgent question: are we truly focusing on the bigger picture, especially with respect to the ocean and the need for large-scale action? The reality is that we need immediate, impactful measures. Our priority should be fast, large-scale improvements, primarily by removing stressors from ecosystems to enable their recovery.
We cannot afford to delay while details are being debated—there is a need for innovation that delivers actionable, clear, and timely information, easily understood by both decision-makers and communities. Degradation of marine ecosystems results from multiple stressors, including pollution (such as agricultural runoff, sewage, and fish farming), overfishing, construction, shipping, and other human activities. Identifying and managing these primary stressors is essential to allow ecosystems to regenerate and thrive.
The marine technology community has a vital role in this mission, providing tools that offer detailed, large-scale insights. These innovations empower stakeholders within marine ecosystems to protect and sustain their environments, thereby supporting their own livelihoods and the health of the planet.
How to cite: Brocke, H., den Haan, J., Lee, M., and Tamborrino, L.: Urgent Action Needed: Leveraging Marine Technology for Large-Scale Restoration of Marine Ecosystem Health , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-620, https://doi.org/10.5194/oos2025-620, 2025.
Seabird populations declined worldwide since 1970. Recent global review showed that invasive species, bycatch, exploitation of marine resources and climate change are the main threats to seabirds. These multiple threats, acting in combination, are also a common situation in the Mediterranean basin. After a brief global context, we will present specific cases on seabird conservation on Port-Cros and Calanques National Park (NP), located in the south east of France. Archipelago of Port-Cros NP is housing the main breeding population of Yelkouan Shearwater, listed endangered in France, while the Scopoli’s Shearwater, vulnerable in France, mainly breed on Calanques NP. Long-term demographic survey and GPS tracking conducted on both archipelagos, supplied by LIFE projects, allowed scientists and managers to obtain crucial information about shearwater biology (e.g., reproduction, survival, moulting strategy), behaviour at colonies (in sexual and nest selection, interactions with introduced species and con-specifics), and behaviour at sea (diving ecology, flight height, feeding sites and global distribution). We showed that the main driver of shearwater population dynamic was the adult survival. This crucial population parameter for a long-lived seabird was relatively low compared to other study sites. At land, shearwater populations are threatened mainly by cats and rats. More recently on Port-Cros NP, wild boars are suspected to weaken the soft substrate where Yelkouan shearwaters dig their burrows. We will discuss about the mesopredator release theory that was not confirmed here by the field results of a concrete cat control management plan. We will show the population dynamics changes of cats, rats and seabirds after several years of management and will discuss of further research questions and concrete management actions targeting islands where shearwater population survival is most at risk. More recently, threats at sea have been investigated through the use of GPS-tracking to estimate space use of seabirds, mortality due to transnational bycatch and recent threat that can emerge from new offshore wind farms. In a recent study, it was revealed that Spanish longliners kill an average of up to 3% of French Scopoli’s shearwater colonies each year. Spanish bycatch is therefore accelerating the decline of the French shearwater populations. As shearwaters are long-distance travelers especially when they undertake extensive foraging trips off breeding colonies and along migration routes, they require an international approach to marine conservation. Concomitantly, our GPS tracking reveals that the area dedicated to deployment of offshore windfarm in “Golfe de Fos” was largely used by both shearwater species to their foraging activities. A GPS program, taking place up to 2028, will allow researchers to investigate for a potential avoidance effect compared with previous years before the turbines were installed.
How to cite: Bonnaud, E., Courbin, N., Bourgeois, K., Besnard, A., Grémillet, D., Debize, E., Fournial, P., Avargues, N., and Mante, A.: Mediterranean seabirds under global threats: a long-term demographic and spatial project within National Parks highlighting the need to preserve shearwater populations., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-721, https://doi.org/10.5194/oos2025-721, 2025.
The Tridacninae subfamily of giant clams is essential for the biological functioning of coral reefs in the Indo-Pacific region. Although there has been seen rise in the commercial mariculture of giant clams in developing countries in the Indo-Pacific region, there is still a deficiency in understanding the factors that influence the growth rate of Tridacna species. In this study, we intend to tackle the scarcity of understanding by investigating the factors that influence the growth rate of T. maxima under culture condition. These factors include seasonal fluctuations, temperature, mantle colours, density of zooxanthellae, and light energy absorption. I t was revealed that the growth patterns of this species are influenced by monthly and seasonal fluctuations, as well as parameters like as temperature, mantle colours, density of zooxanthellae, and light energy absorption. The monthly and seasonal fluctuations in growth rates are directly linked to temperature variations. Specifically, extreme temperatures in winter and summer are associated with reduced growth rates, whereas mild temperatures in spring and fall are associated with higher growth rates. The colour of the mantle also indicated a potential three-way interaction between the growth rate, the colour of the symbionts, and the density of zooxanthellae. i.e. Individuals with brown-colored symbionts displayed higher growth rates and a greater density of zooxanthellae. The number of zooxanthellae varied significantly among different colour variants. Brown individuals had much higher concentrations of symbionts in comparison to blue-brown and blue individuals. Understanding the multifaceted links among environmental conditions, symbiotic interactions, and growth dynamics is crucial for developing successful conservation and management methods for protecting T. maxima populations.
How to cite: AbouElmaaty, E., Mohamed, A., Farg, E., and Hanafy, M.: The role of zooxanthellae in the growth of the giant clam Tridacna maxima in outdoor aquaculture system, Red Sea, Egypt, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-732, https://doi.org/10.5194/oos2025-732, 2025.
Reef fishes maintain many key ecological functions and services for coral reefs. Interactions with their environment have the potential to mediate their distribution, habitat use, and contribution to ecological processes. However, rising anthropogenic pressures and climate change have begun to alter reef environments, modify reef architecture, and disrupt food web dynamics through targeted fishing practices. We examined the impact of habitat structure (rugosity and fractal dimension), biophysical conditions (coral cover, depth, temperature, chlorophyll-a, and wave exposure), and anthropogenic pressures (effluent pollution, fishing pressure, and nearshore development) on biomass, species richness and ecological function in terms of functional diversity and trait-based composition of reef fish communities. Across 89 coral reef sites, we captured fine-resolution Structure-from-Motion photogrammetry and conducted stationary point count surveys to record fish populations. Habitat structure emerged as the primary driver of reef fish biomass, species richness, functional richness, and functional divergence, though biophysical factors also played a role. Traits of reef fish, including diet, grouping behavior, and position in the water column, were all largely influenced by habitat structure in ways that aligned with expectations when considering habitat preferences, foraging behaviors, and predator-prey dynamics. We predicted populations across different reef regimes, characterized by high and/or low values of rugosity, fractal dimension, and coral cover, and found that degraded reefs will support smaller communities with limited traits, which will likely translate to losses of ecosystem functions and services. We highlight the main factors influencing species diversity, trophic structure, and the complexities of ecological communities. Our findings suggest that habitat structure in tandem with well-known biophysical factors can provide insight into reef fish community patterns and should be prioritized as additional metrics when monitoring reef fish populations across space and time.
How to cite: Asbury, M., Schiettekatte, N., Kindinger, T., Richardson, L., and Madin, J.: Fish community composition and functional diversity is determined by biophysical factors and habitat structure. , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-768, https://doi.org/10.5194/oos2025-768, 2025.
In the West African mangrove ecosystems, oysters (Crassostrea tulipa) and bloody cockles (Senilia senilis) play crucial roles both economically and in ensuring local food security. However, these bivalve species face significant threats mostly from overexploitation, environmental degradation, and climate change impacts. These challenges endanger their sustainability, and the livelihoods of the dependent local communities. Previous research detailed the ecophysiology, reproductive cycles, stock dynamics, and recruitment patterns of the two species. The present study focuses on the planktonic larval stages of C. tulipa and S. senilis in the Sine Saloum ecosystem (Senegal). This critical life phase is essential for maintaining stocks and a better understanding is key to sustain an effective management of artisanal shellfisheries. Here, we aim to describe the occurrence, distribution and development of larvae of these two species in the Sine Saloum, to assess the diversity of associated zooplankton communities and the effect of hydrological variables on the patterns observed.
Based on the assumption that larval occurrence correlates with low salinity and high temperature, a bimonthly spatial survey across seven sites in the Sine Saloum estuary has been underway during monsoon season. Plankton samples were collected using two different nets (53µm and 100µm mesh size) and environmental parameters were measured. Plankton samples were analyzed using PlanktoScope and Zooscan at the new West African Aquatic Quantitative Imaging platform (PIQAAO) hosted at the Dakar-Thiaroye Oceanographic Research Center (CRODT), Dakar Sénégal. Based on the images acquired, a learning set is produced to develop a machine learning model for plankton classification, including bivalve larvae. After presenting the context of the study, we will share and discuss the initial results of the classification algorithm and observed changes in the plankton community in connection with hydro-climatic patterns.
This survey will establish a baseline for describing the plankton community composition in the Sine Saloum ecosystem and more generally for the West African coasts. More specifically, the results of this research will provide critical insights into the under-documented planktonic phase of two major bivalve species, contributing to scientific recommendations for sustainable management of their exploitation. These findings are also key in the context of developing aquaculture activities, especially for the oyster.
How to cite: Biteye, A., Thomas, Y., Pondaven, P., Stemmann, L., Makhlouf, N., Diouf, J. E., and Diouf, M.: Investigating how zooplankton monitoring can support shellfisheries in mangrove ecosystems of West Africa, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-779, https://doi.org/10.5194/oos2025-779, 2025.
The intricate relationship between trophic levels in marine ecosystems remains largely unexplored, particularly in the Southern Ocean. To investigate the complex composition of water constituents, notably the phytoplankton community, we used machine learning techniques to classify six bio-optical classes from a comprehensive ocean-color data time-series. In situ data from the Southern Ocean further characterized these classes by predominant phytoplankton types. Biologging data from southern elephant seals revealed that 60% of prey-catch attempts were concentrated within the diatom-dominated class, despite its lower regional frequency. Seals exhibited enhanced foraging activity efficiency and prolonged residency periods, up to 42 consecutive days, in diatom-rich waters compared to 5-10 days in other classes. These findings suggest a preference among southern elephant seals for diatom-rich waters, indicating a selective foraging behavior influenced by the phytoplankton community’s structural composition rather than total biomass alone. This preference underscores the intricate interplay between marine top predators and ecosystem dynamics, hinting at mechanisms through which phytoplankton structure shapes seal behavior and performance.
How to cite: Sari El Dine, Z., Guinet, C., Picard, B., Thyssen, M., Duforêt-Gaurier, L., and El Hourany, R.: Influence of the phytoplankton community structure on the foraging activity performance of southern elephant seals within the Southern Ocean , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-973, https://doi.org/10.5194/oos2025-973, 2025.
An integrated analytical approach is proposed for monitoring and assess the ecological status of the coastal marine ecosystems in West Africa subject to strong anthropogenic pressures. This approach is based on a certain number of conceptual foundations, i.e. guiding principles resulting from methodological constraints identified and discussed in a previous study (Jouffre et al. 2023 - WP4 PESCAO-DEMERSTEM project) and which will be recalled here. These foundations are dictated above all by a major operational objective : that of the routine production of quantitative results, easily interpretable, as robust as possible, and able to be used within the framework of scientific support for public policies related to environmental and fisheries sustainable management in west-african countries. Following from the previous considerations, the approach is mainly based on the estimation of simple ecosystem indicators adapted to the field data available in this region. Thus several of these indicators are directly derived from historical data series from national scientific trawling campaigns available in several countries of the region from the period of the 1980s to present (in Guinea, Senegal and Mauritania). They are calculable and their updating is possible routinely using R script. This is among others the case for indicators designed for the West African marine macrofauna biodiversity monitoring, a set of indicators on which we will focus in this presentation. Temporal (multi-decadal series) and/or spatial estimates of such indicators will be presented and discussed in order to concretely illustrate our approach and its implementation on concrete data. Based on this Guinean case study, our conclusion will address the question of the potential advances that a periodic and generalized monitoring of West African coastal ocean waters based on this indicator methodology could bring. We will try to highligth why it could achieve a very useful – even major – contribution in terms of scientific information on the health, dynamics and future trajectory of the ocean, and on its conservation and sustainable uses, in a region that remains largely under-documented with regards to these aspects.
How to cite: Jouffre, D., Diallo, I., Laziri, W., Thiaw, M., Tfeil, B., Soumah, M., Camara, M. L., and Demarcq, H.: A standarized approach of data based indicators to monitor long-term evolutions and track biodiversity losses in West african marine ecosystems: Description of the approach and implementation in Guinea., One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-985, https://doi.org/10.5194/oos2025-985, 2025.
As urban populations grow, coastal landscapes are becoming increasingly dominated by diverse forms of artificial coastal structures. This ‘Ocean sprawl’, the extension of artificial structures into the marine environment, poses significant threats to the health and functioning of both estuarine and marine ecosystems. More recently eco-engineered has focused on tackling the loss of biodiversity through creating novel habitats with features such as tide pools, pits, grooves, and towers that promote biodiversity within artificial environments.
Eco-engineered rock pools were installed in an artificial causeway in Galway, Ireland in 2013 (n=80) to monitor the increase in biodiversity. Sampling was based on a timeline reflective of ‘ecological succession by inhibition’ within tidal rockpools. Rockpool sampling occurred a) in 2014 (month 12) using non-destructive methods to confirm early colonisation by r-strategists and their potential to function as a rockpool habitat, b) in 2015 (month 24) using destructive sampling to determine taxonomic biodiversity and c) in 2023 (7.5 years later since the last destructive sampling) using destructive sampling to confirm the presence of a mature benthic community in addition to the rockpool water was collected and filtered for the presence of microplastics (MPs)
Results of modelling showed that the change in physical oceanography surrounding the causeway resulted in the establishment of two different habitats. The exposed rockpools were effective at maintaining biodiversity over long periods no overall significant increase in the species richness (t (23.09) = -0.37, p=0.72). In addition, the rockpools retained their functional diversity. However, the community composition of similar rockpools on the exposed western side the causeway, reflecting both the upper and lower shore height, when compared over time showed a significant difference (PERMANOVA Pseudo-F = 19.063; p=0.001). In contrast the sheltered rockpools hosted a sedimentary habitat with a much reduced faunal diversity similar to the adjacent shoreline.
MPs were recorded from all artificial pools on both the exposed and sheltered side. There were significantly more microplastics found per litre of water in the pools at the upper shore height than in the lower shore pools. The quantity per rockpool was highly variable, 14.7± 8.35 MPs recorded from the exposed rockpools and 10.7 ± 6.9 MP in the sheltered pools which had become inundated with sediments, thus failing to function as rock pools as intended. Furthermore, the rockpools recorded on average 19.6 ±15.3 MP L-1 are deemed a hotspot for the bay with significantly higher numbers recorded than from the surface water in Galway Bay in previous studies.
The findings can be utilized to inform the architectural design requirements of future coastal engineering projects and planning policies around the world, thereby establishing guiding principles for the field of eco-engineering standards. Furthermore, this study suggests the possibility of real strategies for mitigating and monitoring maritime pollution through concrete solutions.
How to cite: Nash, R., McGeeney, O., Boucheron, E., Pagter, E., Dabrowski, T., Periro, D., Firth, L., Frias, J., and Tansley, M.: Eco-engineering: a concrete solution to increasing biodiversity and monitoring microplastics. , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-987, https://doi.org/10.5194/oos2025-987, 2025.
Arborescent benthic organisms are ecosystem engineers which provide three-dimensional complexity to the substrate.
When multiple organisms cluster in dense aggregations, they form a forest-like seascape, called marine animal forest.
Each organism is a physical obstacle to the flow and transport is expected to be attenuated in the canopies of those forests in proportion of the canopy obstruction. Flow measurements were carried out in mesophotic coral forest-like seascapes in the Atlantic (Canary Islands, Caribbean islands) and the Mediterranean Sea (Eastern and Western). The flow velocity was recorded at high frequency (2Hz-8Hz) over 3 m above the bottom with acoustic Doppler profilers, simultaneously inside and outside aggregation patches of various species exposed to various flow types (tide, wind-driven). This comparative study evidences that significant flow attenuation in the canopy of mesophotic coral forests is a common feature.
Flow attenuation in marine animal forests generates local conditions suitable for small size species and stages, explaining the higher biomass and diversity in marine animal forests. Local flow attenuation may also enhance the resilience of the forest itself, increasing the retention of canopy forming species’ larvae and food.
How to cite: Pagès, N., Guizien, K., Otero-Ferrer, F., Consortium, U. T. P., and Bramanti, L.: The canopies of coral forests, an hydrodynamic perspective, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1041, https://doi.org/10.5194/oos2025-1041, 2025.
Marine and coastal environments host a great biodiversity and supply multiple services for human activities, such as food and jobs availability. However, these zones are also affected by anthropic pressure and are particularly vulnerable to climate change. In order to protect its marine ecosystems and foster a sustainable use of the marine resources, the European Union adopted the Marine Strategy Framework Directive in 2008. This directive tasked each Member State to define a strategy to reach a “Good Environmental Status” (GES). Among the descriptors used to monitor GES, the assessment of the eutrophication level is of particular importance as 46% of coastal waters suffer from eutrophication. Then, marine strategies comprise regular assessments of the marine environment to monitor impact of national programmes and measures to improve the state of marine waters.
To perform these assessments, in situ measurements may not be sufficient due to their relatively low frequence of sampling, and their limited spatial coverage. Nevertheless, the combination of in situ data with satellites observations meet the need for the assessment strategies. While in situ measurements provide crucial ground truth references, satellite observations offer a high frequence of revisit and allow to document large spatial area. The usefulness of the ocean colour parameters will be presented. Indeed, parameters derived from ocean colour supply a wide range of information on the state of the marine waters, notably the chlorophyll concentration and the sea water transparency.
The developed methodology and metrics to detect eutrophication event in the French coastal area in collaboration with the French Office of the Biodiversity (OFB) will also be presented.
How to cite: Bretagnon, M., Bryère, P., Jutard, Q., Prat, A., and Mangin, A.: Ocean Colour observations in support of European Marine Framework Directives, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1126, https://doi.org/10.5194/oos2025-1126, 2025.
Ship echosounders are essential tools for observing the distribution of organisms within the water column. They enable the study of deep pelagic fauna, likely the most extensive and abundant animal community in the global ocean, yet also one of the least studied. Until now, observations have been constrained by costly and clearly insufficient fishing efforts in one of the most vast and challenging ecosystems in the planet. This situation can now be alleviated through the use of sonar observations. Every day, national research fleets worldwide cover thousands of kilometers, equipped with the most advanced, calibrated, multi-frequency sonars available. Transit routes between scientific missions cover extensive ocean areas, crossing biogeographic provinces, current systems, and eddies. However, sonars are rarely turned on, and even when they are, the data is seldom accessible. This represents a monumental deployment of observational instruments, with daily vessel operation costs ranging from 20,000 to 50,000 euros, which is currently being underutilized. The reasons for this are varied, including jurisdictional issues in foreign national waters and a lack of resources to adequately operate sonars, centralize, process, and make data available. In this communication, we show the current gaps in the spatial and temporal distribution of sonar observations on a global scale. We also estimate how many observations we would have today if national research fleets had recorded and shared transit data over the past 10 years. In addition, we will present potential solutions, as the recent initiative submitted to the French Oceanographic Fleet to collect and deliver transit sonar data to the scientific community, as well as the international initiative GAIN, aimed at developing the first global sonar database updated on a regular basis. Most importantly, this communication seeks to foster dialogue among scientists, policymakers, and legal experts attending the One Ocean Science Congress and the Third United Nations Conference on the Oceans, with the goal of finding solutions to this international challenge.
How to cite: Ariza, A., Lebourges-Dhaussy, A., Berger, L., Menkes, C., Habasque, J., and Ryan, T.: The untapped potential of transit echosounders for monitoring global pelagic fauna, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1150, https://doi.org/10.5194/oos2025-1150, 2025.
The association of epifaunal communities with marine macroalgae has not yet been studied on the Cape Verde Peninsula (Dakar, Senegal). Macroalgae were collected at sea during the warm season (July) from stations around the Cape Verde Peninsula to investigate their association with epifaunal organisms. A predominance of amphipods was noted across the entire epifaunal community. The abundance of this order was higher on the macroalgae Corallina officinalis. The highest epifaunal density was observed on the genus Ulva sp. A significant relationship was observed between the diversity and abundance of epifaunal communities and macroalgal species. However, there was no significant relationship between the biomass of the macroalgae and the biomass of the epifauna. The methodology used in this study could be replicated on a larger spatial and temporal scale. This would provide deeper insights into the communities hosted by macroalgae within the context of the growing blue economy, encouraging future exploitation of macroalgae and addressing biodiversity loss.
Keywords: Epifauna, Macroalgae, Dakar, Senegal.
How to cite: Ndiaye, I., Brehmer, P., Ndour, I., Diatta, Y., and Ndiaye, M.: Epifauna Associated with Macroalgae in Senegal (Northwest Africa), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1262, https://doi.org/10.5194/oos2025-1262, 2025.
The synergy between satellite data, ocean transport modeling and in-situ measurements is relevant to improve the forecasts of the strandings of the invasive algal species Sargassum in the tropical Atlantic Ocean, in the Caribbean Sea and on the Brazilian coast. A methodology for the detection of Sargassum species and their temporal monitoring (hourly to daily) based on remote sensing techniques has been proposed using a multi-sensor satellite data analysis (Low Earth and Geostationary orbits). The spatial distribution of the stranding has been examined from satellite sensors observing at a spatial resolution ranging from 20 m to 5 km. The validation of the methodology was performed using in-situ data acquired in the Caribbean Sea. Finally, alert bulletins have been designed for end-users such as territorial authority, tourism, and fishers to address societal issues. This study enables to propose an integrative approach of the Sargassum stranding issues based on the synergy between satellite data, on knowledge of their spatio-temporal distribution and on model transport forecast. The improvements of ocean modeling of dynamics benefit societal authorities to better respond to the risks induced by the more frequent and intense Sargassum blooms in the Atlantic Ocean.
How to cite: Minghelli, A. and the SargAlert project: Integrative Approach for Operational Sargassum Stranding Forecasts, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1265, https://doi.org/10.5194/oos2025-1265, 2025.
Coastal areas are hotspots of human activity and are among the most productive ecosystems, providing essential resources and services. However, these zones are increasingly under pressure from human activities and climate change, which threaten their ecological balance and long-term sustainability. Remote sensing provides a crucial tool for monitoring coastal areas, allowing for timely detection of environmental changes and human impacts. More specifically, ocean color on coastal waters is a key parameter where significant progress can be made, especially in developing new algorithms and making relevant data products more accessible. The "Ocean Color" Scientific Expertise Consortium under the ODATIS data hub, part of the Data Terra Research Institute (CNES), has identified a series of innovative products and algorithms that address the scientific community's needs at a national scale in France. To this end, ACRI-ST has been tasked by CNES to process a medium-resolution archive of ocean color data (300m) specifically for the French metropolitan coastlines. This project focuses on applying coastal-specific atmospheric corrections and biogeochemical algorithms that meet thematic scientific needs, based on input data from MERIS, MODIS, and OLCI sensors. The resulting coastal products are then made publicly and freely available through a user-friendly web interface. This presentation will cover the data production, validation processes, and public dissemination efforts undertaken within this project. The initiative will, among other things, enable a comparison of a wide range of products and provide access to a long-term archive of qualified ocean color data. This work could potentially be extended to other regions of the world in the future.
How to cite: Prat, A., Doxaran, D., Vantrepotte, V., Bretagnon, M., Bryère, P., and Mangin, A.: Production of an ocean color archive focused on the coastal waters of Metropolitan France on behalf of the ODATIS data hub to support scientific research and marine studies, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1266, https://doi.org/10.5194/oos2025-1266, 2025.
Mayotte, a tropical French island located in the northern part of the Mozambique Channel in the western Indian Ocean, boasts a unique lagoon housing a diverse marine ecosystem that is particularly sensitive to anthropogenic pressures. At the heart of this ecosystem lies the planktonic food web. Plankton, including phytoplankton and zooplankton, support the biological production of many habitats, such as coral reefs and seagrass beds, by providing the main source of carbon and nutrients for higher trophic levels. However, this vital food web is under increasing pressure, such as eutrophication, caused by nutrient inputs linked to human activities.
To assess the health of this ecosystem and monitor its response to pressures, it is crucial to develop indicators targeted at the planktonic food web. The typology of this food web enables us to better understand how plankton, the base of the food chain, reacts to environmental changes, in terms of carbon production and energy transfer. For example, phytoplankton, which vary in size and abundance according to nutrient concentration, directly influence the trophic chains that depend on them, and the availability of carbon for higher levels.
Ecological network analysis (ENA) is a valuable tool for quantifying the structural and functional properties of these planktonic food webs. By examining carbon transfer pathways, this method can identify key indicators such as food web stability, nutrient recycling capacity and planktonic community productivity intensity. Thus, in more nutrient-rich waters, the food web may become more active but less stable, while in less productive environments, the food web tends to be more organized and resilient.
The integration of planktonic food web typology and ENA indices provides an effective framework for adaptive management of the Mayotte lagoon. By closely monitoring planktonic responses to anthropogenic pressures, this approach helps to better orient conservation strategies, thereby preserving the ecological balance of this exceptional lagoon.
How to cite: Chkili, O., Rodier, M., Marchesseaux, G., and Chevalier, C.: Study of Planktonic Food Webs in the Mayotte Lagoon: Towards Adaptive Ecological Monitoring in the Face of Anthropogenic Pressures, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1275, https://doi.org/10.5194/oos2025-1275, 2025.
Rocky shores, a key component of coastal ecosystems, are characterized by canopy-forming brown macroalgae that support high biodiversity and provide essential ecosystem services. These environments are increasingly impacted by multiple stressors, yet there remain significant knowledge gaps regarding their impacts on biodiversity. For instance, the effects of eutrophication on rocky shore biodiversity have been extensively studied in macroalgae, but much less is known about these effects on epifauna biodiversity inhabiting these biogenic habitats, predominantly characterized by gastropod species.
Disentangling the effects of eutrophication from other natural or anthropogenic drivers is challenging as epifaunal communities exhibit complex ecological responses to local conditions such as the substrate type, shore height, wave exposure, or canopy density preference. However, rocky-shore communities are easy to sample and monitor due to their accessibility and ease of identification. These characteristics make them potentially valuable for monitoring changes in coastal environments through citizen science programs.
Our main research question here is whether a citizen science program focusing on epifauna can help assess the effects of eutrophication on rocky shore gastropods, which in turn would make it a suitable indicator to monitor changes in coastal ecosystems. We explore this question in a transdisciplinary initiative driven by a co-construction process between scientists and citizens, the ESPOIRS project. This project is based on an existing citizen science project “Algues Brunes et Bigorneaux” (“Brown Algae and Winkles”) which was established in 2011 and previously documented changes in epifaunal rocky shore communities due to anthropogenic stressors at a regional scale. To correctly address these questions with a citizen-science protocol, a spatial sampling design is necessary to control for confounding factors. To this end, we collaboratively developed with citizen scientists a sampling framework focusing on estuaries where eutrophication is most pronounced, while minimizing wave exposure, a factor known to significantly shape intertidal communities. Together with volunteers, we investigated seven estuaries across Brittany (France), representing diverse environmental conditions and varying concentrations of inorganic nitrogen (NO₂ + NO₃) from spring to fall 2024. In each site, we estimated the density and size structure of key gastropod species found in mid-eulittoral brown macroalgae belts (e.g., Fucus vesiculosus and Ascophyllum nodosum) with a 0.1 m² quadrat. Additionally, the macroalgal communities within and around each quadrat were described to both control for other local effects and investigate whole community responses. This study provides new insights into understanding responses of rocky shore biodiversity to anthropogenic pressures and opens new prospects for assessing environmental quality through citizen science.
How to cite: Serranito, B., Rintz, C. L., Bouet, A., Le Viol, I., Mebarki, C., Beauvois, A., Ysnel, F., Goberville, E., Feunteun, E., and Leroy, B.: Evaluating eutrophication effects on rockys-shore epifauna with citizen science, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1301, https://doi.org/10.5194/oos2025-1301, 2025.
The appeal of using VHR satellite imagery to conduct biodiversity studies particularly in large, remote and inaccessible ocean surfaces where traditional survey methods are limited or impractical, had already been raised by various scientific communities, including the IWC.
The southwestern Indian Ocean basin is a true sanctuary for large whales. Considering the global context of climate change, past and new threats, this area reveals the urgency of addressing significant gaps in the integrated understanding of spatial ecology of protected cetaceans’ species (population abundance, spatial distribution and migration trajectories, inter-annual variability factors), and the characterization of human pressures (legal and illegal) at sea,
The THETYS project consisted of an unprecedented proof of concept on the scale of the South-West Indian Ocean, aiming to assess the potential for detecting humpback whales and their environmental conditions using Very High Resolution satellite images.
The project aimed at real innovation in the reliability of the method, by combining remote sensing engineering and marine field ecology in a synchronized way (1) to ensure unequivocal identification of species, (2) to confirm the visual annotations that will be made from the images, and (3) to promote “indigenous knowledge” with local scientific teams and/or NGOs. In addition, satellite programming is a non-intrusive and flexible method for conservation and decision making.
In 2021, with the support of the NGO Abyss and the producers of spatial data the possibility of detecting humpback whales from VHR satellite images by negotiated programming has been confirmed.
The pilot sites selected for this study are : the south African coasts, Madagascar and La Reunion.
For this presentation, we will showcase a sample of the best resolutions on the global satellite imagery scene; and the first step of how to "label" these images by visual detection of the target species and human activities, and by organizing ground truth campaigns synchronized with satellite taskings.
How to cite: Ovize, M., Adam, O., Nguyen Duy-Bardakji, B., Doh, Y., Ecalle, B., and Denis, B.: Study of humpback whale populations in the southwest Indian Ocean from Very High Resolution satellite images, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1347, https://doi.org/10.5194/oos2025-1347, 2025.
Fisheries, though inherently renewable, are currently in alarming decline due to a range of environmental and human-induced factors. Ensuring sustainable management of these resources requires comprehensive studies and continuous monitoring, taking into account all interacting parameters to better understand resource dynamics and adapt management strategies accordingly.
This study examines the impact of artisanal and recreational fishing along a 16-kilometer stretch of coastline, encompassing five coastal municipalities. Data were collected through observations and surveys at 22 sites, revealing the presence of 26 artisanal fishing boats and 262 recreational fishing vessels in the area. These figures indicate a substantial fishing pressure, despite the relatively simple techniques used in both types of fishing.
The influence of these fishing activities on the local fish populations is evident in the quantities of fish caught. The number of fishers and the volume of catches highlight a significant impact on the local ichthyofauna. The main species targeted include Mullus barbatus (red mullet) from the Mullidae family, with a capture frequency of 50 ± 5.89% primarily by artisanal fishers, and Diplodus sargus (white seabream) from the Sparidae family, mostly caught by recreational fishers, with a capture frequency of 45.83 ± 3.08%.
The findings raise concerns about the sustainability of these species within the study area, underscoring the need for a more extensive and detailed assessment. Future research should aim to extend the survey duration and expand data collection to build a robust statistical and biological database for the region. Such a database would allow for a more accurate evaluation of stock status and the impacts of fishing on fish populations.
Additionally, it is recommended to implement monitoring programs focused specifically on the stocks of red mullet and white seabream to prevent overfishing and potential resource collapse, as these two species are the primary targets of artisanal and recreational fishing in the area.
To refine management strategies further, a multi-species, multi-gear approach is proposed. This approach would explore the relationships between various fish species and the different types of fishing gear used. Understanding these interactions could provide insight into the broader impacts of fishing on different stocks, supporting a more sustainable and ecosystem-based management approach.
In summary, this study reveals the substantial influence of artisanal and recreational fishing on local fish populations along this coastline. Ongoing research and targeted conservation measures are essential to safeguard these resources against overexploitation. Expanding monitoring efforts and adopting comprehensive, multi-species management approaches will provide a more solid foundation for sustainable fisheries management, ensuring the long-term viability of both the fisheries and the ecosystems they support.
How to cite: Kribel, F. and Refes, W.: Effects of Artisanal and Recreational Fishing on the Ichthyofauna of an Urbanized Coastal Zone of Algiers , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1382, https://doi.org/10.5194/oos2025-1382, 2025.
Knowledge of the structure and distribution of benthic biotopes is essential for marine conservation. It is a prerequisite for the assessment of the environmental status of marine ecosystems, the designation of protected areas, and the design of monitoring programmes to evaluate the effectiveness of conservation measures. Building on extensive datasets with high spatial coverage from ongoing national monitoring programmes, targeted environmental impact assessments, and basic research studies, we analysed benthic communities of the North Sea to characterize sublittoral biotopes and evaluate their ecological value within the network of seafloor habitats in this region. The application of advanced geo-statistical methods revealed the complex spatial structuring of the seafloor with a considerable diversity of benthic biotopes. Specific infauna associations were identified and characterized by their species inventories and composition of characteristic species. Supposedly isolated biotopes shared common features, highlighting connectivity which may crucially enhance their resilience against disturbance. Further, the distribution of key species demonstrated substantial contribution of some biotopes to ecosystem functioning. Our extensive monitoring of the biodiversity of benthic species communities and habitats essentially improved our understanding of the structure and functioning of the North Sea ecosystem, supporting the development and implementation of management tools and conservation measures in the face ongoing environmental change and anthropogenic disturbances.
How to cite: Beermann, J., Gutow, L., Heinicke, K., and Pesch, R.: Biodiversity monitoring in the southeastern North Sea: identification and characterization of threatened benthic biotopes, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1409, https://doi.org/10.5194/oos2025-1409, 2025.
Monitoring biodiversity at large spatial scales is essential for understanding the impacts of climate change on coastal ecosystems and offering insights for environmental management. Here, we compile the results of four large-scale spatial studies along the southeastern Brazilian coast, in which we investigate ecological patterns and processes in rocky shore communities. Altogether, the studies highlighted that abiotic factors, particularly ocean temperature and wave exposure, are primary drivers of intertidal community composition and structure. These factors not only regulate species distribution and abundance but also influence biological interactions, such as predator-prey dynamics. For instance, cooler upwelling zones supported distinct species assemblages compared to warmer areas. Predation impacts weakened with increasing wave exposure. Urbanisation adds another layer of complexity to these natural gradients. Coastal areas near major urban centres experienced nutrient and pollutant influxes that altered species composition and abundance. Anthropogenic factors may reshape intertidal communities, amplifying natural stressors and highlighting the need for large-scale monitoring to distinguish human impacts from natural variability. By linking biodiversity patterns to environmental and human-driven variables across extensive spatial gradients, these studies provide insights into the underlying mechanisms governing coastal biodiversity and offer predictive capacity for future changes. Macroecological approaches are essential to address the unique environmental variability of the southeastern Brazilian coast, as these studies revealed that ecological responses often differ across scales, from localised interactions to broad patterns spanning hundreds of kilometres. Such findings are crucial in a climate change context, as they offer a foundation for understanding how ocean warming, sea level rise, and shifts in upwelling might alter population structure and community dynamics in the future. Collectively, our results argue for a comprehensive, scale-integrated monitoring framework that captures both spatial and temporal biodiversity changes. As marine ecosystems face increased temperatures and extreme weather events, large-scale monitoring can provide early indicators of biodiversity shifts, enabling adaptation strategies. Understanding how intertidal communities respond to climate and human-induced changes is crucial for building resilience in these vital ecosystems, ensuring that coastal management efforts can better protect biodiversity and ecosystem functionality.
How to cite: Pardal, A., Christofoletti, R., Martinez, A., Cordeiro, C., and Ciotti, Á.: Large-scale biodiversity monitoring on rocky shores in Brazil: Informing coastal management for climate-resilient strategies, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1420, https://doi.org/10.5194/oos2025-1420, 2025.
The Eastern Red Sea is a known biodiversity hotspot encompassing an extensive fringing coral reef ecosystem. However, this region faces alarming relative declines in elasmobranchs (sharks, in particular) populations related to heavy fishing pressure. At the same time there is inadequate data on these species’ distribution, diversity, and ecology. For many species of large shark found in the Red Sea, little information exists on their habitat extent and related environmental drivers, limiting effective conservation strategies. Our study use an expansive dataset (CERSE) to shed light on the vertical distribution of local elasmobranchs, their environmental associations and correlation with abiotic factors. We identify critical habitats and hotspots of elasmobranch abundance in the Eastern Red Sea, pivotal for their preservation and in informing the design of robust conservation measures. We highlight the remarkable ability of certain elasmobranchs to endure prolonged periods of hypoxia, potentially linked to the unique temperature characteristics of the Red Sea.Understanding this relationship may provide valuable insights into the plasticity of certain elasmobranchs and how these adaptations could aid in their survival amid ongoing climate change and the associated decline in oxygen levels. Overall, our data on the elasmobranch population trajectories in the Red Sea region reinforce the alarming declines highlighted by previous studies in this region, emphasizing the critical need to strengthen policy enforcement for their protection. By enhancing conservation efforts in the Eastern Red Sea, we can help ensure the long-term survival and ecological stability of these important species.
How to cite: Frappi, S., Qurban, M., and Duarte, C. and the Sofia Frappi: Distribution, depth use and environmental associations of sharks and rays (Elasmobranchii) in the eastern Red Sea, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1453, https://doi.org/10.5194/oos2025-1453, 2025.
The Black Sea's marine ecosystem houses a diverse phytoplankton community crucial for the region's biogeochemical processes. Recent attention has focused on comprehending the taxonomy and community dynamics of Black Sea phytoplankton. High-performance liquid chromatography (HPLC) serves as a potent analytical tool for pigment separation and identification in phytoplankton samples. This study examines HPLC pigment data collected between 2006 and 2019 during 12 oceanographic bio-optic campaigns in the Black Sea. The research investigates taxonomic composition and community structure of the phytoplankton community. Analysis of the dataset involved employing various machine learning and bioinformatics tools. Additionally, the dataset was used for chemotaxonomycal classification and for the development of phytoplankton functional type (PFT) regionalized model. All these methods aimed to identify distinct phytoplankton groups and their relative abundance throughout the campaigns. Results indicate that the Black Sea phytoplankton community is predominantly composed of diatoms and dinoflagellates, with varying contributions from other groups such as prasinophytes, haptophytes (coccolitophores), and chlorophytes. Additionally, the study discerned diverse patterns of community composition and pigment ratios across the campaigns, revealing spatial variations in phytoplankton community structure influenced by factors like nutrient availability and water column stratification. This research significantly contributes to understanding the taxonomy and community structure of Black Sea phytoplankton through the application of advanced multivariate analysis techniques.
How to cite: Canuti, E.: Phytoplankton Biodiversity in the Black Sea: A Comprehensive Study of Community Structure based on High-Performance Liquid Chromatography (HPLC) Pigment Analysis , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1437, https://doi.org/10.5194/oos2025-1437, 2025.
Marine heatwaves (MHWs) have been intensifying in frequency and magnitude, posing significant threats to marine biodiversity, particularly to sessile benthic species such as the red gorgonian, Paramuricea clavata. This study examines the status of P. clavata populations in the upper mesophotic zone (30 m – 60 m) of the French Mediterranean, a depth range that may offer partial refuge from MHW events. By analyzing data from more than 40 populations, we evaluate the health, density, and growth dynamics of these populations in the context of rising temperature anomalies and anthropogenic pressures. The findings provide insights into the vulnerability of mesophotic ecosystems and underscore the need for targeted conservation strategies in collaboration with Marine Protected Areas to mitigate the impacts of climate change on these critical habitats and support sustainable management initiatives.
How to cite: Estaque, T., Bianchimani, O., Cheminée, A., Garrabou, J., Hartmann, V., Mérigot, B., Sartoretto, S., and Schull, Q.: Rising Marine Heatwaves: Current Status of Red Gorgonian (Paramuricea clavata) Populations in the Upper Mesophotic Zone of the French Mediterranean, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1494, https://doi.org/10.5194/oos2025-1494, 2025.
Elasmobranchs, including 79 shark and 120 ray species worldwide, face severe endangerment due primarily to fishing pressures and marine pollution. This study investigates the health of fishery resources affected by the 2019 oil spill in Northeast Brazil, focusing on histopathological changes in the liver, kidney, and gills, as well as the presence of polycyclic aromatic hydrocarbons (PAHs) in the muscle tissue of Rhizoprionodon porosus (RP) and Hypanus guttatus (HG). Age and time of exposure to oil (TEO) were estimated, and organ and total histopathologic indexes (Iorg and Itotal) were determined following Bernet (1999). Additionally, lesion severity was assessed using the Zimmerli (2007) approach. Results show that 74% of the 71 elasmobranchs sampled exhibited significant histological changes, with lesion scores exceeding 40, indicating severe, chronic stress. Notably, 54% of these were rays (H. guttatus), with gills identified as the most affected organ across both species. Significant differences in Itotal scores were observed between species, though sex, sexual maturity, age, and exposure time had no significant impact. This pioneering histopathological assessment highlights elasmobranchs as valuable bioindicators and underscores the environmental impact of Brazil's most severe coastal oil spill to date.
How to cite: Duarte-Neto, P., Rey, B., da Silva, F., Luna, T., Souza, F., Carreira, R., and Lessa, R.: Health Assessment of Two Coastal Elasmobranch Species from the Northeast Region of Brazil, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1524, https://doi.org/10.5194/oos2025-1524, 2025.
This study assesses the reserve effect on fish assemblages within the Larvotto Marine Protected Area (MPA), a small, fully protected, and highly enforced urban MPA, established in 1976 in Monaco (Mediterranean Sea), a highly urbanised coastal zone. Using a five-year dataset from underwater visual censuses, we analysed fish density, size, and biomass across two key habitats: artificial rocky substrates and Posidonia oceanica meadows, comparing data from within the MPA to nearby unprotected areas. Results show a pronounced habitat-specific response, with significantly higher fish biomass on artificial substrates inside the MPA, while Posidonia oceanica meadows displayed no significant biomass difference between protected and unprotected zones. These findings demonstrate that well-enforced MPAs in urbanized settings can deliver substantial ecological benefits, providing valuable insights for policymakers and advancing our understanding of MPAs in complex coastal environments. Integrating urban MPAs into broader conservation frameworks could enhance the ecological resilience of coastal ecosystems by complementing “residual” MPAs typically located in less disturbed areas. This approach can help reconcile the intensifying use of coastal zones with ambitious 2030 global conservation targets, contributing meaningfully toward the effective protection of 30% of Earth’s surface.
How to cite: Ventura, P., Gautier-Debernardi, J., Di Franco, E., Francour, P., Di Franco, A., and Pey, A.: Ecological benefits and Habitat-specific fish responses in a small fully protected urban MPA, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1559, https://doi.org/10.5194/oos2025-1559, 2025.
Since 2011, extreme strandings of Sargassum spp. have been recorded off the west coast of Africa, the southwest Atlantic, the Caribbean Sea and the coast of Florida, resulting in significant ecological and economic impacts, such as increased trophic level, development of associated and harmful algae, competition for oxygen, changes in habitats and decline in food chains. This work investigated the behavior and structural complexity of these masses using multifractal analysis applied to georeferenced images from the SargAlert (ANR) consortium. The images obtained are products classified as 0 (no Sargassum spp.) and 1 (Sargassum spp.), covering two sets: CWA, with 167 daily images for some months from 2020 to 2024, and MNQ, with 263 images with five-day observations in the period from 2018 to 2022. The analyses included pixel quantification (particle count, average particle area and total coverage) and multifractal parameters such as lacunarity(Λ), width of the multifractal spectrum(Δα), spectrum asymmetry (f(Δα)) and dominant singularity (α0). Regions with vortices, identified visually in the images, were isolated and checked separately, subdivided into east (VE) and west (VW). The images were also partitioned into spatial squares of 8 km for NMQ and 93.2 km for CWA, allowing the creation of distribution maps of the multifractal parameters. The results indicated that the images of both areas have geometric multifractal properties, with generalized dimensions following D0>D1>D2. The singularity spectra of the CWA are more symmetrical than those of the NMQ. In NMQ, there was a high correlation between the particle count and the total coverage area, while Λ and the average area showed a negative correlation with Δα, f(Δα) and α0. In 2019, there was high coverage and concentration of particles at the start of the year, followed by an increase in Λ and the average number of particles. In 2021, the images showed high Λ and average particle area, followed by an increase in total coverage and particle count, and then a return to high Λ and average particle area values at the end. For CWA, there was a positive correlation between α0 and coverage area, with a negative correlation between Λ and f(Δα). The 2020 images stood out with the highest Λ and f(Δα) values. In vortices, VE and VW showed similar behavior: the total area correlated positively with the average particle size, as did α0 and particle count, as did Δα and f(Δα). The distribution maps showed areas of greater dispersion, complexity and symmetry. In the CWA, the vortices showed low values for f(Δα), high values for α0 and moderate values for Λ. The multifractal approach was shown to be effective in assessing the structural complexity of Sargassum spp. and provides new information that can support management decisions and mitigate the impacts of these algal masses.
How to cite: Gustavo, F., Chevalier, C., Laval, M., Courtrai, L., Costa de Silva, A., Descloitres, J., Aimene, Y., Salazar, A., Minghelli, A., and Duarte Neto, P.: UNDERSTANDING THE PHENOMENON OF Sargassum spp. MASS DYNAMICS USING FRACTAL GEOMETRY THROUGH ORBITAL PRODUCTS, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1589, https://doi.org/10.5194/oos2025-1589, 2025.
Continuous observations of non-human species allow us to study them and understand their activities, their interactions with their peers and their environment. They also allow us to assess their intelligence and adaptability, for example by describing their cultural transmission and/or detailing the innovative attitudes they display to attract a partner, capture prey or escape a predator. These observations are difficult to carry out for cetaceans in their natural environment, due to their high mobility and low visibility in the depths. However, visual and acoustic data are necessary to characterize individuals, their behaviors and their interactions. To meet this challenge, we designed and built the Cetoscope. Equipped with 6 cameras and 4 hydrophones, this tool makes it possible to identify cetaceans in the vicinity, record their vocalizations to complete their vocal repertoire, and reconstruct their trajectories in 3D. We also have developed a software to track cetaceans in 3 dimensions and provide metadata, such as time, estimated distances, type of sounds emitted. After designing such a tool, the next step was to calibrate the video cameras and hydrophones to check the synchronizations and reconstruct, a posteriori, the observed scenes, from the recorded data. Finally, we used this tool to track a group of bottlenose dolphins off La Réunion Island, Indian Ocean. Our results allowed us to identify the individuals in the group (adult/juvenile, male/female) and also to show that some individuals are vocal while others are silent. We showed that vocal dolphins play the role of scouts in the sense that they approach the Cetoscope to scan it and learn more about it. Our study will be used to characterize the impacts of human activities, in particular how these cetaceans react to whaling tourism. Eventually, we would be able to better understand how cetaceans perceive humans in their environment and assist in decision-making regarding approaches and observation of cetaceans in a context of increasing tourism.
[1] Doh, Y., Ecalle, B., Delfour, F., Pankowski, C. Cozanet, G., Becouarn, G., Ovize, M., Denis, B., and Adam, O. (2023). Performance assessment of the innovative autonomous tool CETOSCOPE© used in the detection and localization of moving underwater sound sources. J. Mar. Sci. Eng., 11, 960. https://doi.org/10.3390/jmse11050960
[2] Gillespie, D.; Palmer, L.; Macaulay, J.; Sparling, C.; Hastie, G. Passive acoustic methods for tracking the 3D movements of small cetaceans around marine structures. PLoS ONE 2020, 15, e0229058
How to cite: Doh, Y., Denis, B., Ecalle, B., Adam, O., and Ovize, M.: Cetoscope : an innovative material and software to observe the cetaceans in their wild environment, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1286, https://doi.org/10.5194/oos2025-1286, 2025.
The Eastern Tropical Pacific (ETP), a highly productive and biodiversity-rich region stretching from Baja California in Mexico to the Gulf of Guayaquil in Ecuador and encompassing islands like the Galápagos, provides vital habitats and migratory corridors for a diverse array of marine megafauna, including threatened and endangered species of sharks and rays. The ETP Marine Corridor (CMAR), a regional collaborative effort between the governments of Colombia, Costa Rica, Ecuador, and Panama, was established in 2004 to protect migratory routes and habitats by linking existing Marine Protected Areas (MPAs) into a cohesive network, expanding existing MPAs and addressing overfishing and illegal fishing. CMAR is a model for transnational conservation efforts, but significant challenges remain in ensuring the long-term protection of elasmobranchs that rely on habitats that remain overfished for part or most of their life cycle. Estuaries and mangrove fringed bays on the coast of Central America are critical breeding and nursery habitats for many shark and ray species, yet remain outside of the CMAR framework and are vulnerable to anthropogenic impacts. Our team is leveraging environmental DNA (eDNA) detections to track seasonal patterns of habitat use by migratory and resident shark and ray species in 16 estuaries of the Pacific of Panama and Costa Rica where traditional censusing methods would be cost-prohibitive and logistically challenging to conduct at that scale. We are using a two-pronged approach to address science gaps and inform policy. First, we are targeting whole elasmobranch assemblages in water and a sediment eDNA time-series to characterize spatial and temporal turnovers and identify key hotspots for elasmobranch diversity. Second, we are using highly sensitive species-specific assays to detect the occurrence of critically endangered elusive species. Results indicate that the distribution of sharks and rays is heterogenous in space, with a few estuaries playing a disproportionately important role in the life histories of multiple species. We detected the presence of the critically endangered largetooth sawfish in an estuary where there are no previous confirmed sightings, highlighting the value of eDNA for rapid assessment of rare and elusive species. Together, our results provide a strong scientific foundation to expand management and protection to key continental coastal habitats within the CMAR framework.
How to cite: Leray, M., Chichaco, Y., Wilkins, L., Rodriguez-Arriati, Y., Ali, V., Reque, J., Domínguez Domínguez, O., Lacayo, M., Phillips, N., Zanella, I., and Quintero, H.: Tracking sharks and rays in continental estuaries of Central America: Using eDNA to inform conservation in the Eastern Tropical Pacific, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1502, https://doi.org/10.5194/oos2025-1502, 2025.
High-latitude oceans are among the most vulnerable regions to a warming climate. Historically covered by sea ice for much of the year, these areas are now experiencing accelerated environmental changes, such as increasing atmospheric and ocean temperatures, resulting in rapid glacial melt and calving. Sermilik Fjord, located in southeastern Greenland, is an Arctic fjord system influenced by marine-terminating glaciers and characterized by complex bathymetry and distinct water masses, including warm, saline Atlantic Water (AW), cold, saline polar water, and cold, fresh subglacial meltwater. These characteristics create a diverse and productive ecosystem, with unique physical characteristics among the inner fjord, outer fjord, shelf, and slope/off-shelf regions.
This study aims to explore and compare zooplankton community assemblages across Sermilik Fjord, specifically focusing on the presence or absence of AW in the surface waters (40-200 m depth). This research will determine relationships between zooplankton community composition and AW, define community structure for each region, and identify indicator species associated with specific regions or water masses. Field collections were conducted using 29 samples from a bongo sampler deployed to a depth of 100 m. Vertical profiles of temperature, salinity, and other parameters were collected using a CTD, providing a detailed understanding of the water column structure and the presence of different water masses.
About half of all stations that zooplankton were collected at had AW present in the surface waters. A hierarchical cluster analysis determined five key zooplankton community clusters in the fjord, and distinct separation between communities that had a presence or absence of AW in the surface waters. Zooplankton statistical analyses will be accomplished through a NMDS on community clusters. SIMPER analysis identified euphausiids and chaetognaths as key contributors (over 50%) to community dissimilarity. Diversity analysis using Shannon and Simpson indices revealed considerable variability in zooplankton community composition across samples. Low Shannon values (e.g., Upper fjord with H' = 0.032 and Mid-fjord with H’ = 0.011) and high Simpson values (e.g., Fjord Mouth, D = 0.65) indicated dominance by a single species, suggesting low community diversity. In contrast, samples near the glacier-terminus (H' = 1.10, D = 0.66) and coast (H' = 0.87, D = 0.55) exhibited higher diversity and evenness. These findings highlight areas with both high species dominance and more evenly distributed communities, reflecting spatial differences in zooplankton community structure. Preliminary results indicate potential gradients in community composition, with warmer water species and higher zooplankton abundance associated with AW presence in surface waters. Distinct communities were also observed between regions influenced by glacial meltwater and those characterized by warmer AW influx.
This work contributes to our understanding of the ecological dynamics of Greenland's fjords in response to climate change, highlighting the importance of zooplankton as key players in Arctic marine ecosystems. It further emphasizes the challenges and urgency of studying these vulnerable regions, as they undergo profound shifts in their physical and biological environments.
How to cite: Carlton, H., Ciannelli, L., Bernard, K., Bouchard, C., Roth, A., and Straneo, F.: Exploring Zooplankton Community Structure and Environmental Relationships in a Glacial-Terminating Fjord in Southeast Greenland, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-920, https://doi.org/10.5194/oos2025-920, 2025.
There are many individual biological observation stations in Europe, however there are few and inconsistent links between them. The European Marine Omics Biodiversity Observation Network (EMO BON) is an ESFRI (European Strategy Forum on Research Infrastructures) initiative, coordinated by the European Marine Biological Resource Centre-European Research Infrastructure Consortium (EMBRC-ERIC) to unite marine stations under one centrally organised observation network that uses shared protocols, international standards and agreed policies.
EMO BON is employing omics methodologies for accurate biodiversity monitoring and reporting; it aims to establish a coordinated, long-term, marine biodiversity observation network. It was launched in 2021, and it currently includes 17 marine stations, in 9 countries, ranging from the Arctic to the Red Sea, which regularly collect samples from three different habitats (water column, soft substrates, and hard substrates) and three different communities (microbes, meiofauna and macrofauna).
EMO BON generates high-quality FAIR genomic biodiversity data that are being made periodically available to all interested parties and thereby support constructive dialogue towards a holistic understanding of our ocean.
EMO BON is an OBON (Ocean Biomolecular Observing Network) endorsed project and thus is it one of the UN Ocean Decade Actions. EMO BON has become the European contribution to the global marine biodiversity observation efforts and plans to collaborate and integrate further with other global entities. Preliminary results, based on 4 TB of data from 700 samples, will be presented as example case studies of the added value of including genomic data into conventional monitoring schemes. As such, EMO BON data could be used to meet the objectives of the Kunming-Montreal Global Biodiversity Framework (GBF) since they can be used to identify the impact of stressors, such as climate change and other human activities, to coastal ecosystems.
How to cite: Pavloudi, C. and Soccodato, A. and the EMO BON consortium: Implementing long-term genomic observation in the marine environment: preliminary results from the European Marine Omics Biodiversity Observation Network (EMO BON), One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-636, https://doi.org/10.5194/oos2025-636, 2025.
With the increasing availability and efficiency of sound recording devices, bioacoustics is becoming a leading tool to monitor loud populations and/or behaviors, owing to its long-term, non-invasive nature. This particularly applies to marine mammals that are among one of the most vocal contributors of underwater soundscapes. Passive acoustic monitoring (PAM) facilitates such studies, yet the process of manually annotating data remains time-consuming and labor-intensive for any human. The use of deep neural networks (DNN) is becoming increasingly common on the field, but it still remains challenging. Indeed, numerous complexities arise, from data acquisition phase (wide vocal repertoire even from one sound source, high variability of surrounding environments, scarcity of vocal activity resulting in imbalanced datasets, very low signal-to-noise ratio (SNR) due to ambient noise) to its pre-processing (noisy labels due to inter-annotators variability, limited availability of large annotated datasets).
Transfer learning methods have shown great performances to tackle these issues, leveraging pre-trained models trained on larger and/or more annotated datasets, and fine-tuning them to suit specific detection/classification tasks. These methods make use of pre-learned embeddings (i.e. data representation in the model’s latent space) to process similar new data and classify them into new classes, learned during the fine-tuning phase.
In this study, we explore the potential interest of Perch (Ghani et al., 2023), a Google model trained on the community-driven database Xeno-Canto which contains thousands of annotated hours of bird songs. Although originally a bird-species classifier, Perch has also proven to be a powerful and versatile embeddings generator, outperforming other models like BirdNet on the Watkins Marine Mammals Sounds Database through linear probing. This finding motivated us to use the embeddings generated by Perch fine-tuned by a Multi-Layer Perceptron (MLP) on the largest labeled underwater acoustic dataset publicly available (Miller et al., 2024), mostly dedicated to low-frequency blue and fin whales vocalizations. To evaluate the generalization ability of this model, we used validation acoustic datasets from different geographical areas and/or from different temporal ranges.
A keypoint of this work is that the main results are based on the largest publicly labeled acoustic database (Miller et al., 2021) and fairly compared with state-of-the-art methods thanks to the first benchmark published along with this dataset (Schall et al., 2024).
How to cite: Jean-Labadye, L., Dubus, G., Cazau, D., Farrugia, N., and Adam, O.: A little bird told me : transfer learning for automatic detection and classification of blue and fin whales low-frequency vocalizations in the Southern Ocean, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1575, https://doi.org/10.5194/oos2025-1575, 2025.
The bottlenose dolphin (Tursiops truncatus) is a common cetacean along the eastern Pacific coast, spanning from Canada to Chile. While widely distributed, the species exhibits region-specific adaptations influenced by environmental and biological factors. In Costa Rica, bottlenose dolphins form a neritic population in the coastal waters of Golfo Dulce and Golfo de Nicoya, whereas Cocos Island hosts a pelagic population that has developed distinct morphological traits due to their diet. Although Cocos Island is geographically remote, threats such as bycatch still affect cetacean populations. While the feeding behavior of these dolphins is relatively well-documented, there is little information on their distribution patterns and social structures. This study aims to enhance conservation efforts in international waters of the Eastern Tropical Pacific, by investigating the spatiotemporal distribution of bottlenose dolphin aggregations at Cocos Island. Monitoring was conducted from 2017 to 2022 using the Protocol for the Ecological Monitoring (PRONAMEC) of Aggregations of Aquatic Mammals, developed by Costa Rica’s National System of Conservation Areas. The study area, Cocos Island National Park, was divided into four quadrants, each surveyed over a four-day monitoring effort. A total of 36 field trips were carried out: 20 during the rainy season and 16 in the dry season. For each dolphin sighting, observers recorded the group composition (adults, juveniles, pups), geographical location, date, and time. Statistical analysis was performed to identify significant differences in sightings per field trip across seasons, quadrants, and years, as well as variations in group size and composition. Results indicated a slight decrease in the number of sightings per field trip over the years but an increase in individuals per sighting. Although trends were observed, no significant differences were found between the first and last years of monitoring or between seasons. Aggregations generally comprised three to five individuals, with the northeastern quadrant showing the highest number of sightings per field trip, followed by the southwestern. A significant difference was found only between the northeastern and northwestern quadrants during the rainy season. Groups with only adults were the most frequently observed by statistical differences. The marked increase in individuals per sighting in 2020 and 2021 may be related to the suspension of fishing activities and reduced tourism during the COVID-19 pandemic. The consistent presence of juveniles and pups across all quadrants and seasons suggests that Cocos Island serves as a critical habitat for feeding, reproduction, and juvenile development. However, this pattern was not observed in 2022, when juveniles and pups were notably absent. The distribution pattern, especially in the northeastern and southwestern quadrants, suggests that dolphins may rely on nearby seamounts as feeding grounds, given their high productivity. Continued monitoring is recommended to corroborate these trends over time and to support conservation efforts in this vital marine area.
How to cite: Fernández, S., Ulate, K., and Golfín, G.: Bottlenose dolphin (Tursiops truncatus) aggregations at Cocos Island National Park, Puntarenas, Costa Rica, between 2017-2022, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-911, https://doi.org/10.5194/oos2025-911, 2025.
Bioblitzes have been proven a successful approach for biodiversity monitoring with volunteer participation. Bioblitzes are intense periods of biological surveying, in the framework of a friendly competition among all the participants, in an attempt to record all the living species within a designated area over a continuous time period (e.g., usually 24 hours). The use of citizen science platforms, which allow sharing photos of organisms among the participants and validating these observations in a collaborative way, facilitates the design of bioblitzes with a much larger number of volunteer participants and larger areas to explore. Many examples (Diaz-Calafat et al. 2024, Herrando, S. et al. 2012) have shown the success of bioblitzes in terrestrial ecosystems.
However, designing a bioblitz to monitor marine biodiversity is too risky, as rough sea conditions can completely ruin this type of event designed for such short periods of time. To avoid these potential risks an extended bioblitz has been designed for monitoring the sea: the BioMARathons.
The BioMARathon concept has been validated in the coastal region of Catalonia (North-East of Spain, with the local name of BioMARató) using MINKA (minka-sdg.org) as the citizen science observatory for reporting and validating observations.
Over the past 4 years, the BioMARató has been promoted in the Catalan coast, extending the competition over the summer period (from late April to the mid October). More than 850 volunteer participants have contributed with almost 250.000 observations, more than 2900 species, some of them first records of alien species. The BioMARathon approach has been replicated in the north of Portugal in summer 2024 and also a pilot in the Liguria region in Italy.
BioMARathons require more complex community structures for participation, following the conceptual Janus framework (Liñan et al. 2022): in addition to volunteers and academia, the framework includes the communities of enablers as well, with the role of mobilizing participants and providing resources (diving suits, guided snorkel tours, underwater cameras…) to facilitate volunteer participation. Three communities of enablers have participated in the different BioMARathons: the Catalan Federation of Underwater activities (FECDAS) along the Catalan coast, BIOPOLIS working in the North of Portugal, and the“Posidonia Green project” initiative in Italy.
The results of the BioMARathons demonstrate to be a very powerful and cost-effective solution for engaging people to report observations in marine environments and could be extended to many coastal areas in the future for global monitoring of coastal areas.
How to cite: Companys, B., Liñan, S., Salvo, V.-S., Salvador, X., Monteiro, C., Riera, S., and Piera, J.: BioMARathons as a formula to reduce the gap of knowledge in marine biodiversity with volunteer participation, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1260, https://doi.org/10.5194/oos2025-1260, 2025.
Diatoms are tiny, unicellular organisms that can be identified by their frustule, a siliceous cell wall. They can be used to compare streams, lakes, wetlands, oceans, estuaries, and even certain ephemeral aquatic environments because they are present in nearly all aquatic habitats. Their value as potent and trustworthy environmental indicators has long been acknowledged. Their high abundance and species diversity are ascribed to their usefulness. Surface sediments from the coastal and continental regions of southwest Kerala, which include wetlands, river, and estuarine complexes, have been used for the current diatom study. Thirty grab samples were gathered for the investigation from the Vembanad wetland, Alleppey back waters, Asthamudi lake, Peruman, Poovar estuaries and, Periyar, and Manakudi rivers. The diatoms taxa recorded includes both planktic and benthic forms viz. Cyclotella, Thalassiosira, Campylodiscus, Actinoptychus, Aulacoseira, Triceratium favus, Biddulphia, Nitzschia, Cocconeis, Gomphonema, Tabellaria, Navicula, Ulnaria ulna, Caloneis, Luticola, Neidium, Achnanthes, Achnanthidium, Gyrosigma, Encyonema, Surirella, Stauroneis, Sellaphora, Pinnularia, Grammatophora, Eunotia and many others to count. In the study it was observed that the diatom assemblage varied on different scales either for river sediments, wetland or estuarine complexes. It was noted that in the river sediments freshwater benthic diatoms with very high diversity and frequency were recorded and also indicate organic pollution activity in the vicinity of the river channel. In the wetland and back water sediments, the planktic diatoms were recorded in high frequency both for the freshwater and marine forms while the benthic diatoms were in low counts. This was probably due to the higher water levels in the wetland and back waters. The change in freshwater and marine diatoms was reflected where the marine incursion was either limited or freshwater inundation was high. The estuarine samples however recorded varying frequencies of freshwater and marine diatom assemblages owing to their proximity to sea. Thus it can be postulated that the diatoms are one of the major biological entity that can record and witness the variable limnological aspect of environment and climate change. In a broader sense it can be visualized that the proxy can be helpful in fine tune observations for palaeolimnological and palaeoenvironmental reconstruction in geological times.
Keywords: - Diatoms, Kerala, wetland, limnology, palaeoenvironment
How to cite: Tiwari, P. and Thakur, B.: The Study of Diatoms variability along the Vembanad wetland, Kerala and implications to limnology, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-106, https://doi.org/10.5194/oos2025-106, 2025.
