Initiatives including the WMO framework for climate research, the 2021-2030 UN Ocean Decade and the G7 Future of the Seas and Oceans Initiative have identified the increase of sustained, multidisciplinary integrated ocean observing systems as an absolute priority. Integrated observing systems require data from global (e.g., GOOS, EMODNET) and regional observation systems to be assimilated into numerical and statistical models. Their long-term sustainability is dependent on the development of cost-effective technologies that improve observing capacities (including spatial and temporal resolution) while reducing costs, aiming for a “more environmentally friendly ocean observing system”.
The North Sea, one of the most well-observed and heavily exploited shelf sea regions, provides a unique opportunity to study the effects of climate change and human activities on the coastal ocean. As part of the session, we will use the North Sea as a case study to illustrate these effects, providing insights relevant to broader marine environments.
This session brings together multidisciplinary perspectives to bridge technological advancements, scientific research, and practical solutions to address the current state and future threats to our oceans. We invite submissions from observational and modelling studies on, but not limited to, the following topics: technological developments for studying abiotic and biotic factors; advancements in methods for data collection, processing, curation, and information extraction; primary production; biogeochemical cycling of carbon, nutrients and oxygen; monitoring, reporting and verification of CDR; ocean acidification, climatic variability and extreme events; circulation patterns, land-ocean interactions; biophysical interactions and sediment dynamics; effects of natural and anthropogenic pollution on biota; marine ecology, biodiversity and benthic and pelagic community dynamics; marine ecosystem restoration and socio-economic impacts, including economic valuation of natural capital.
Healthy oceans and sustainable development are the core contents of the "Ocean Decade" plan put forward after the United Nations Ocean Conference. Maintaining the health of marine ecosystem is an effective guarantee for the realization of marine service and output functions, an important support for sustainable economic and social development, and a major issue of global concern. In many cases, we manage the ocean without understanding the ocean, because we do not really understand the past, present and future of the ocean, and the most important thing is that we lack the knowledge and hands to perceive, recognize and master the ocean. The health of the oceans depends largely on the state and safety of the organisms in the oceans. So, the theme of how to evaluate the health of the ocean should also be biology. We are concerned about marine eutrophication, because eutrophication can cause red tides and the increase of many harmful algae, which in turn will lead to the accumulation of algae toxins in shellfish that feed on algae, which will have a serious impact on human health and life when humans eat these shellfish. For a long time, our monitoring of the ocean emphasis on the environment, not the ecosystem, and the monitoring content is mainly chemical factors, with emphasis on pollutants, but the monitoring of organisms in the ocean is relatively weak, and the criteria we have long used to classify the state of the ocean are expressed by "several types of seawater", which is far from enough for the healthy ocean and sustainable development. Unable to meet the requirements of marine health assessment, we need to establish a marine health assessment system with marine organisms as the main body to monitor the ocean from the marine ecosystem The goal of measurement should be biological change and the environmental factors that lead to biological change.
How to cite: Sun, S.: A new observation and assessment system is needed to maintain the ocean health and achieve sustainable development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14482, https://doi.org/10.5194/egusphere-egu25-14482, 2025.
We obtained historical and observational data on phytoplankton communities from 1959 to 2023 to explore the responses of the phytoplankton community structure to long-term environmental changes in the southern Yellow Sea (SYS), China. The results revealed a decrease in the proportions of diatom cell abundance within the phytoplankton community by 8%, accompanied by a corresponding increase in that of dinoflagellates. Dominant phytoplankton species were mainly chain-forming diatoms before 2000, and large dinoflagellate species from the genera Tripos and Noctiluca increased their dominance after 2000. Warm-water phytoplankton species have increased in dominance over the study period. Correlation analysis revealed that the ocean warming and alterations in nutrient structure (N/P and Si/N ratios) were mostly responsible for the long-term evolution trend, and these changes may result in an increase in dinoflagellate harmful algal blooms, reduced efficiency of the biological carbon pump, and heightened hypoxia in the future, which should draw our attention.
How to cite: Guo, S. and Sun, X.: Long-term variation of phytoplankton communities in the southern Yellow Sea (1959~2023), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4648, https://doi.org/10.5194/egusphere-egu25-4648, 2025.
Microplastics (MPs) are widely distributed in the ocean and can be ingested by fish. Despite fish being a major source of aquatic protein for humans, no study has yet addressed how to reduce the risk of human exposure to MPs when consuming fish. This study investigated 1,075 fish from 37 species across representative fishing areas, analyzing MP presence in various tissues, including gills, intestines, and muscles, to assess fish food safety comprehensively. MPs were found in 36.28% of gills and 39.63% of guts, but none were detected in muscle tissues. Fish from upper layers had higher MP abundances and smaller average sizes compared to those from deeper waters. A significant negative correlation was observed between the MP abundance in fish and their length and weight. The global per capita MP consumption from captured fish, including all tissues and muscles, is approximately 5.60 × 104 items/year. Hence, to minimize MP exposure, humans should prioritize consuming only fish muscle and selecting fish from deeper waters and larger sizes whenever possible. Optimizing fish consumption patterns could reduce human exposure to MPs and associated health risks.
How to cite: Meng, L. and Sun, X.: How to reduce human microplastic exposure risks through optimized consumption choices of fish from seawater?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7626, https://doi.org/10.5194/egusphere-egu25-7626, 2025.
Tidal flats, a vital coastal wetland habitat in the land-sea transition zone, serve as breeding grounds, nurseries, and habitats for numerous estuarine and offshore fish species. Moreover, they play an indispensable role in maintaining fish biodiversity. Regrettably, the cumulative impacts of intensive human activities and climate change have significantly disrupted the landscape structure and functionality of tidal flats. This has led to the degradation of fish habitats and an even more severe loss of suitable living environments for fish populations. Despite the importance of understanding these dynamics, in-depth research into the changing ecological patterns within the coastal zone and their implications for fish communities remains limited. Jiangsu Province, a pivotal development hub within China's Yangtze River Delta region, is endowed with rich tidal flat resources and a densely populated area. To address the knowledge gap, this study aimed to leverage remote sensing imagery of Jiangsu’s coastal zone to extract landscape distribution data. By constructing an ecological security evaluation framework, we comprehensively analyzed the landscape ecological patterns of tidal flats. Additionally, we employed advanced techniques such as ultra-high resolution mass spectrometry and high-throughput sequencing to explore fish diversity characteristics. Integrating these with multi-source data analysis and model simulations, we sought to uncover the intricate relationships between landscape ecological patterns and fish biodiversity characteristics in the coastal zone. The findings were consistent with previous research on the thermophilic ratio of fish communities in the southern Yellow Sea and the offshore areas of Jiangsu. In different landscape ecological pattern groups, spatial heterogeneity was evident in the composition and relative abundance of fish species. When it comes to the protection of tidal flats, it is essential to consider not only the area changes in a specific region but also the structure and function of these areas. Integrating the results of the analysis on tidal flat ecological patterns and fish diversity, preventive, proactive restoration, and rehabilitative measures should be implemented to safeguard and manage coastal areas. Ultimately, this research endeavors to deepen our scientific understanding of the role of fishery resources in the sustainable development of the coastal zone. Based on our findings, we proposed targeted recommendations for the conservation and management of the coastal zone's spatial pattern, thereby contributing to the long-term health and resilience of this critical ecosystem.
How to cite: Cheng, S. and Cao, L.: The influence of landscape ecological pattern changes of tidal flat on fish community in the coastal area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21737, https://doi.org/10.5194/egusphere-egu25-21737, 2025.
High-resolution carbon isotopic records from organic and carbonate carbon reveal an unprecedented multi-decade decline in stable isotopic compositions over the past millennium. These records were obtained from laminated cores collected in the San Lázaro Basin (SLB), a semi-closed basin off the Baja California Peninsula, Mexico. The SLB is influenced by suboxic waters at depth and lies beneath the southern boundary of the California Current System. Isotopic analyses of two planktic foraminifera species, N. dutertrei and G. ruber, show a decreasing trend in carbon isotopic compositions over the past 80 years, mirroring the trend seen in atmospheric CO₂, albeit with slightly lower slopes. These trends are likely driven by the influx of anthropogenic CO₂ into surface waters of the California Current, a manifestation of the Suess effect in the upper ocean. The differences in slope are likely due to the combined influence of vertical mixing driven by dominant northwest winds, which bring nutrient- and inorganic carbon-rich waters with relatively heavier isotopic values, and the equatorial advection of northern waters carrying anthropogenic CO₂ in this highly productive eastern boundary current.
How to cite: Contreras-Pacheco, Y. V., Abella-Gutierrez, J. L., Vallejo-Espinosa, G., and Herguera, J. C.: The Onset of Anthropogenic Carbon Invasion in the Surface Waters of the Southern California Current, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-757, https://doi.org/10.5194/egusphere-egu25-757, 2025.
As climate change progresses, increasing attention is being devoted to potential impacts on ecosystems and resources under sustained warming. For models that resolve climate impacts on global marine animal biomass, however, most work to date including model intercomparisons have largely focused on the period up to 2100. Here we consider projections to 2300 using a collection of five Marine Ecosystem Models (BOATS, FEISTY, DBPM, MArcroecological, and ZooMSS) driven by output from a collection of CMIP6 Earth system models (including CESM2-WACCM and IPSL-CM6A, as well as UKESM1, MIROC-ES2L, and ACCESS-ESM1.5). Initial results from ESMs with online coupled biogeochemical models suggest that although they exhibit a degree of diversity in their ocean warming response, their disagreements about projected primary production are even more pronounced, with the disagreements being not only in amplitude but also in sign.
We explore the long-term impacts of climate mitigation on marine animal biomass, by comparing Marine Ecosystem Model results under high emissions with low mitigation (SSP5-8.5) and low emissions with high mitigation (SSP1-2.6) forcing. If thermal forcing were to dominate the fish biomass through its effect on mortality with a linear response, one might expect an approximately factor of five difference between SSP1-2.6 and SSP5-8.5 projections of marine animal biomass change to 2300. Both regional and global aspects will be considered, with a focus on identifying potential tipping points under SSP5-8.5 forcing that may be avoided through mitigation.
How to cite: Rodgers, K., Bianchi, D., Aumont, O., Blanchard, J., Bopp, L., Buechner, M., Everett, J., Guiet, J., Heneghan, R., Hill, S., Kawamiya, M., Murphy, K., Petrik, C., Richardson, A., Sharma, S., and Yamaguchi, R.: The high value of climate mitigation for global fish biomass to 2300, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14914, https://doi.org/10.5194/egusphere-egu25-14914, 2025.
Oceanic transport and environmental variability are key for structuring marine populations and designing protection and management plans. While previous regionalizations of the Mediterranean Sea have provided valuable insights into objectively discretizing the marine seascape, they only suggest impacts on biogeography without explicitly testing them. Additionally, these studies often overlooked small-scale, high-frequency processes and focused predominantly on near-surface layers, neglecting deeper biomes.
To address these limitations, (i) we utilize a data-assimilative model and remote-sensing observations at high resolution, and (ii) we focus on two Mediterranean species with contrasting ecological traits, including adult phases exploiting both epi- and meso-pelagic layers as well as highly dispersive early-life stages. Our target species are the red mullet (Mullus barbatus), a demersal fish mainly distributed in the continental shelf, and the deep-water red shrimp (Aristeus antennatus), a pelagic marine decapod. Using passive Lagrangian particles advected within two-dimensional flow fields at several depths, we construct networks of connected areas and cluster them to identify hydrodynamic provinces. The average of these provinces reveals recurrent spatial patterns aligned with multiscale oceanographic features. In parallel, we use seawater temperature gridded data and a community detection algorithm to look for regions based on geographical proximity and temperature similarity. It produces clusters that we then average to mean abiotic regionalizations. Finally, we integrate independent observed biogeographies of the target species, and employ statistical modeling to explain these biogeographies as a combined effect of ocean circulation and abiotic clusters. This approach advances our understanding of biogeographical patterns, by deciphering two regimes depending on spatial scales, teasing apart the respective role of oceanic circulation and abiotic variability and how the latter are modulated by the target species’ ecological traits.
This robust framework helps exploring the controls of the spatial organization of marine life and could be used to predict future biodiversity reorganization in the ocean.
How to cite: Rwawi, C., Moltó, V., Berline, L., Nérini, D., and Rossi, V.: Explaining biogeography through ocean circulation and abiotic variability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17616, https://doi.org/10.5194/egusphere-egu25-17616, 2025.
Better understanding of the carbon dynamics in coastal areas is essential to develop metrics to evaluate the efficiency of policies regarding carbon neutrality (i.e. whether the coastal environment, more specifically the Belgian part of the North Sea, acts as a source or sink of carbon to the atmosphere). Over the last 8 years data has been collected from discrete samples (pH, DIC, TA) and data produced by the ICOS coastal stations BE-SOOP-Simon Stevin and the BE-FOS-Thornton Buoy (seawater CO2 concentration). These data are an invaluable source to identify how the carbonate chemistry and air-sea carbon fluxes can be used to determine whether the coastal environment acts as a source or sink of CO2 and assess the acidification state. More specifically, we will present the temporal evolution of pH, DIC, TA, seawater CO2 concentration and air-sea CO2 fluxes from the gathered data. The data show the expected seasonality of carbon dynamics and the link with biogeochemical processes (e.g. phytoplankton blooms) but also trends in the capacity of these areas to absorb or release CO2. Furthermore, the results show a pH stability of these coastal waters, uncorrelated with the increase in DIC. This suggests the influence of biogeochemical processes, such as riverine inputs, nutrient dynamics, and the organic matter remineralisation within the coastal zone. This work will also investigate whether it is feasible to connect such information directly or indirectly to policies relevant to carbon neutrality.
How to cite: Leseurre, C., Theetaert, H., T'Jampens, M., Van Engeland, T., Verbrugge, S., and Gkritzalis, T.: Using the VLIZ ICOS station measurements and discrete samples to assess the carbonate chemistry trends (since 2017) and carbon neutrality of the Belgian part of the North Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6653, https://doi.org/10.5194/egusphere-egu25-6653, 2025.
The North Sea, a highly productive shelf sea, may play an important role in the local carbon cycle by exchanging carbon and nutrients with the Atlantic Ocean and facilitating carbon burial in its sediments. However, understanding the response of carbon burial rates to natural and anthropogenic forcings remains limited in this setting. To address this gap, this study examines long-term trends in carbon burial and their natural and anthropogenic drivers at North Sea-North Atlantic gateway over the past 14,000 years. Sediment cores – both piston core and multi-core (61.5687 °N, 3.0465 °E) – were analysed using a multi-proxy approach including X-ray fluorescence (XRF), lipid biomarkers, (compound specific) isotopes, and dinoflagellate cysts to reconstruct climate change, patterns of primary productivity and origin of the carbon. Chronology was established using radiocarbon dating. Carbon burial rates were reconstructed by calibrating the Br/Ti log ratio with TOC measurements, while the productivity of calcium-bearing organisms was inferred from the Ca/Fe log ratio. The highest carbon burial rates of 8 gC/m²/yr are during the Younger Dryas and coincides with cold bottom water temperatures/high global ice volume and reduced productivity. In the Early Holocene, productivity increased, followed by a gradual transgression, reducing sedimentation rates and thereby carbon burial rates to 2 gC/m²/yr. At around 500 years BP, carbon accumulation rates increased again to approximately 5 gC/m²/yr, likely caused by anthropogenic factors such as deforestation and changes in land use.
How to cite: Hilgen, C., Hennekam, R., van der Meer, M., Reichart, G.-J., and Sangiorgi, F.: Carbon burial at the North Sea-North Atlantic gateway over the past 14,000 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16678, https://doi.org/10.5194/egusphere-egu25-16678, 2025.
The North Sea is a very productive and heavily exploited continental shelf sea that acts as a sink for atmospheric CO2. The balance between carbon buried in North Sea sediments and exported off the northwest European shelf into the North Atlantic is highly uncertain, rendering carbon budgets difficult to make and future changes of the system hard to predict. As part of the NoSE (North Sea-Atlantic Exchange) project, this study evaluates the uncertainty and variability in the exchange (with the North Atlantic) and burial of carbon in the North Sea as simulated by global Earth System Models (ESMs).
From six state-of-the-art ESMs (ACCESS-ESM1-5, CanESM5, CMCC-ESM2, CESM2-WACCM, IPSL-CM6A-LR, NorESM2-LM), the years matching the observational period were selected from the CMIP6 historical experiment (1850 to 2014) and the ScenarioMIP of CMIP6 ssp245 experiment (2015 to 2100).
Here, we compare simulated values for sea surface temperature, salinity, phosphate, alkalinity and dissolved inorganic carbon (DIC) to an internally consistent data product for the northwest European shelf (NWESDAP; 347 datapoints). The models show good agreement for temperature (r2 > 0.8), but weak simulation of salinity (r2 < 0.4). The weak fit is mainly caused by a bad representation of low salinity, whereas in the higher salinity range, the comparison between the models and the observations is better. The model simulation of phosphate shows a weak fit with the observations (r2 < 0.5), mainly caused by a bad model representation of higher phosphate concentrations in the observational dataset. Although the model representation of total alkalinity and surface DIC is weak (r2 < 0.3), the mean observed DIC values are reasonably well represented by the models. As the horizontal flux of DIC is a product of horizontal water transport and DIC concentration, the representation of the variability in DIC might not be as important for calculating lateral fluxes as an adequate simulation of its spatial mean value.
The model ensemble representation of the main in- and outflow areas, as well as representation of the spatial variability of the variables is considered good enough to compare the present-day and the future North Sea carbon cycle.
Using the model ensemble, we will present the spatial and temporal variability in carbon burial, carbon concentrations, horizontal carbon transport and the balance between these components, both for present-day and future climate conditions.
How to cite: Koek, A. C. (., Humphreys, M., Poll, van de, W., and Bintanja, R.: North Sea carbon burial and transport off the northwest European shelf in global Earth system models (ESMs) – validation and variability , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16030, https://doi.org/10.5194/egusphere-egu25-16030, 2025.
Coastal seas are vital players in the global carbon cycle, acting as both sinks and sources of atmospheric carbon dioxide (CO₂). However, their carbon dynamics remain poorly quantified at the spatial and temporal resolutions necessary for regional carbon budget assessments. Enhanced insights are critical for detecting anthropogenic impacts on the carbon cycle and for monitoring the effectiveness of CO₂ removal strategies. The Belgian Part of the North Sea (BPNS), equipped with advanced monitoring infrastructure, offers a unique platform to address these gaps through in-situ CO₂ measurements collected via buoys, research vessels, and other sources. This data collection provides high spatial and temporal coverage, enabling near-real-time estimation of the exchange of CO₂ with the atmosphere in the region.
To estimate the baseline carbon budget for the BPNS at an unprecedented local scale, we applied a feedforward neural network approach capable of achieving a spatial resolution of 1 km and a temporal resolution of 1 day. This analysis spans the period from 2014 to 2024 and incorporates an extensive dataset of sea surface partial pressure of CO₂ (pCO₂) measurements. These in-situ observations were sourced from the Surface Ocean CO₂ Atlas (SOCAT) and the Integrated Carbon Observation System (ICOS) databases. Additionally, we integrated a suite of predictor variables derived from satellite data and oceanographic reanalysis products, including sea surface temperature, salinity, chlorophyll-a concentrations, and suspended particulate matter, all of which are recognized as key factors influencing pCO₂ variability in the BPNS. By combining this calculated sea surface pCO₂ with atmospheric CO₂, we also estimated the air-sea CO₂ flux.
Initial findings reveal that the sea surface pCO₂ reconstruction achieves strong predictive ability for coastal zones, with an R² exceeding 0.80, successfully capturing both local spatial heterogeneity and seasonal variations. Sensitivity analyses highlight sea surface temperature as the dominant predictor, followed by chlorophyll-a and suspended particulate matter, emphasizing the interplay of thermal and non-thermal processes in shaping pCO₂ variability across the BPNS. The seasonal cycle of pCO₂ decreases after winter primarily due to increased CO₂ solubility in cold water and biological spring uptake, and peaks after summer, mainly driven by warming of the seawater and reduced biological activity, leading to an increased release of CO₂. While sea surface salinity exerts a relatively minor influence overall, its localized impact near the Scheldt estuary plume is significant, underscoring the critical role of riverine inputs in modulating regional carbon dynamics. Overall, our findings indicate that the region functions as a net CO₂ sink for the atmosphere.
How to cite: Keppens, M., Roobaert, A., van Langen Rosón, A., Neukermans, G., and Landschützer, P.: High-Resolution Coastal Carbon Dynamics in the Belgian Part of the North Sea Using Machine Learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15600, https://doi.org/10.5194/egusphere-egu25-15600, 2025.
Consistent and quality-controlled data products of marine carbonate system parameters, such as the Global Ocean Data Analysis Product (GLODAP), are needed to investigate the marine carbon cycle and its variability through space and time. However, GLODAP focuses on the open ocean, limiting its utility for understanding the marine carbonate system in shelf seas. While representing only ̴7% of the global ocean area, these areas play an important role in the global carbon cycle. The northwest European shelf (NWES) seas are of particular interest because of their high heterogeneity and expected capacity to absorb, export and bury carbon. Here, we present a new internally consistent data product for this region, the Northwest European Shelf Data Analysis Product (NWESDAP). NWESDAP includes directly measured marine carbonate system parameters (total alkalinity, dissolved inorganic carbon and pH) as well as physical and nutrient variables focusing on the NWES above 1000 m and between 43°N and 70°N. NWESDAP gathers datasets of discrete measurements from research cruises and time-series stations from throughout the water column. Data from estuaries, deltas and fjords are also included. So far, NWESDAP consists of about 18,000 inorganic carbon data points (of which c. 5,000 were already in GLODAPv2.2023) from around 500 research cruise and station datasets, merged into a consistent format. Data quality flags corresponding to quantified systematic and random uncertainties have been assigned to each dataset depending on the measurement method used and other available metadata. As GLODAP-style quality control (QC) based on deep ocean cross-over analysis is not possible in this shallow region, a secondary QC based on parameter distributions and covariances has been conducted to identify suspected erroneous data points and systematic biases in specific datasets, aiming to ensure the internal consistency of the entire product so it can be used to investigate the highly variable marine carbon cycle in the NWES seas.
How to cite: Brandon, M., Humphreys, M. P., Becker, M., and Bittig, H. C.: The marine carbonate system in the northwest European shelf seas: an internally consistent data product (NWESDAP), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3276, https://doi.org/10.5194/egusphere-egu25-3276, 2025.
Shelf seas filter terrestrial inputs of important macronutrients and bio-essential trace metals such as iron (Fe) and manganese (Mn), which support primary productivity and long-term carbon dioxide (CO2) storage in the sediments and the deep ocean. The North Sea is a biologically productive shelf sea and a net sink of atmospheric CO2, yet the exchange of essential (trace) nutrients between the North Sea and the North Atlantic Ocean as well as the role of trace elements in the carbon cycle are poorly constrained. This limits our ability to accurately model biogeochemical interactions and calculate CO2 fluxes in this region. Within the NoSE (North Sea-Atlantic Exchange) project, we investigate the North Sea's role in the Atlantic Ocean's biogeochemical system, focussing on the Norwegian trench for its pivotal role in the nutrient and inorganic carbon outflow to the Atlantic and sediment accumulation. Here, we present an observational dataset of trace metals, nutrients, and marine carbonate system parameters from the first NoSE expedition in May-June 2023. We analyse the spatial distributions, sources and sinks of (trace) nutrients in the water column and discuss their relationships with carbonate system and other hydrographic parameters. We found clear latitudinal differences as well as differences between shallower (< 200 m) waters above the shelf proper and the deeper waters of the trench. Linear correlations between salinity and certain trace nutrients in the surface waters indicated a fresh water source either from the Baltic Sea or the Norwegian rivers and fjords while correlations between turbidity and Fe and Mn concentrations close to the seafloor suggested sedimentary inputs.
How to cite: Adler, M. A., Humphreys, M., Middag, R., and Brandon, M.: Processes driving trace metal, nutrient, and dissolved inorganic carbon distributions in the Norwegian Trench, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10231, https://doi.org/10.5194/egusphere-egu25-10231, 2025.
In aquatic ecosystems, plankton communities generally form the base of trophic webs, and environmental changes are often reflected, or even amplified, in these communities. In the context of anthropogenic climate change, plankton communities could be drastically impacted by rising temperatures and the increase of extreme climate events. The Belgian Part of the North Sea (BPNS) is already heavily influenced by human activity, and extreme climate events could greatly alter the dynamics of the ecosystem. Recent years have seen an uptick in marine heatwaves in the BPNS, which have been associated with unusually prominent Bellerochea sp. blooms and temporary copepod die-offs. As the frequency of these marine heatwaves is projected to increase, it is necessary to gain an understanding of how phytoplankton and zooplankton communities may respond not only to stable temperature change, but also to rapid change. This research therefore aimed first to characterize BPNS marine heatwaves, and second to analyze the corresponding plankton community dynamics. Initially, 30 years of satellite data were used from the National Oceanic and Atmospheric Administration Optimum Interpolation Sea Surface Temperature dataset (NOAA OI SST V2 High Resolution Dataset). Temperature data was used to establish a 90th percentile threshold for marine heatwave detection. Marine heatwaves were then characterized based on intensity relative to the 90th percentile threshold, cumulative intensity (deg. C x days), duration, peak temperature reached, and timing of peak temperature. These results were compared with those from underway temperature measurements at ~3 m depth as well as with CTD temperature measurements, all collected on the RV Simon Stevin. Additionally, we defined and analyzed temperature regions based on both geographical and biological zones. For plankton data, samples were collected monthly (nine coastal stations) and seasonally (with eight additional offshore stations) on board the RV Simon Stevin, with zooplankton data from 2014 onwards and phytoplankton data from 2017 onwards. ZooScan and FlowCam automated imaging sensors were used to quantify zooplankton and phytoplankton, respectively. Plankton dynamics were then analyzed in terms of bloom timings and abundances (dominant groups, diversity indices). Overall temperature data from the BPNS showed similar marine heatwave trends using NOAA satellite data and RV Simon Stevin underway data, and highest temperatures were reached in the summers of 2018 and 2022. At several nearshore stations, the key plankton group Appendicularia had a delayed bloom during the 2022 marine heatwave compared to the 2018 marine heatwave. Ultimately, this parallel characterization of marine heatwaves and plankton dynamics offers insight into the health of the BPNS ecosystem. Furthermore, it offers potential for predicting the responses of phytoplankton and zooplankton to future marine heatwave events.
How to cite: Eske, A., Semmouri, I., Mortelmans, J., Muñiz, C., Hablützel, P., and Janssen, C.: Characterization of Belgian Marine Heatwaves and Their Impacts on Plankton Dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15734, https://doi.org/10.5194/egusphere-egu25-15734, 2025.
The shallow North Sea is characterized by complex hydrography and environmental variability, which affects the air-sea interactions and the skin layer (< 1mm). The skin layer plays a crucial role in air-sea interactions, and understanding its physical dynamics is essential for advancing knowledge in this field. Ocean fronts are predominantly narrow horizontal gradients of oceanic properties separating water masses and can be hotspots for marine biodiversity. Satellites have been used to observe large scale fronts however frontal features exist even on the sub-mesoscale. By leveraging seasonal data from an autonomous surface vehicle, we investigate the spatial and temporal variability of the skin layer at these small scales, with a focus on the role of oceanic fronts in shaping surface-layer dynamics. We use high-resolution measurements (0.1 Hz) of temperature, salinity, GPS data and weather-related variables at discrete depths in the air and water. These measurements are from our self-designed autonomous surface vehicle known as HALOBATES, which is equipped with multiple sensors and rotating glass discs to sample and measure the skin layer. Primarily, we applied a gradient-based algorithm to identify oceanic fronts, characterized by sharp horizontal gradients in temperature and salinity within the skin layer and bulk water (1-meter depth). To ensure that frontal features are accurately isolated, the effect of diurnal warming or cooling were taken into account. We isolated fronts solely on temperature or salinity, and by both parameters to understand the nature and origin of the fronts. Secondarily, we provide results of front detection from a Machine Learning perspective, showing results of deep learning models like Convolutional Neural Networks and an unsupervised clustering algorithm. We also present the results of the underlying bulk water (1-meter depth) to understand the pre-eminence of the observed front. We also investigate possible forcing factors due to sudden changes in the wind speed and direction as well as heat flux components such as solar radiation, precipitation and evaporation. By using continuous data from an autonomous platform over an extended period, our findings will highlight the dynamics of sub-mesoscale fronts in the North Sea and their role in shaping the physical characteristics of the skin layer. The insights from this study are relevant for ongoing research on topics such as heat and gas exchange at the ocean-atmosphere boundary layer which is a good indicator of the climate dynamics of the North Sea.
How to cite: Ayim, S. M., Jaeger, L., Gassen, L., and Wurl, O.: Detecting and Investigating Frontal Dynamics in the Skin Layer of the North Sea Using Autonomous Surface Vehicle Observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3158, https://doi.org/10.5194/egusphere-egu25-3158, 2025.
Understanding the habitats of commercially important pelagic fish is essential for their sustainable management. Pelagic fish species are not only economically significant but also play crucial ecological roles in marine ecosystems. Climate change is reshaping marine environments by altering ocean temperatures, salinity, and other abiotic conditions, which affect the distribution and behaviour of these pelagic fish.
In light of the challenges posed by a changing environment, this research examines how climate change, according to Shared Socioeconomic Pathways (SSPs) scenarios, impacts the habitats of three commercially significant pelagic species in the North Sea: Atlantic herring (Clupea harengus), Atlantic mackerel (Scomber scombrus), and European seabass (Dicentrarchus labrax). Mechanistic niche models were developed using temperature and salinity data from BioOracle and validated using 655,389 species occurrence records from EMODnet.
Model validation, conducted through Root Mean Square Error (RMSE) and visual inspection of predicted versus observed distributions, demonstrated good alignment between observed presence and predicted suitable habitats, supporting the models' reliability despite some regional mismatches due to uneven data distribution. The analysis estimated Habitat Suitability Index (HSI) values and observed distribution patterns, focusing on how optimal suitability shifted over time, independent of longitudinal variations. The HSI was classified on a scale where values were considered optimal (HSI ≥ 0.75), suboptimal (0.5 < HSI < 0.75), and poor (HSI ≤ 0.5). The impact of climate change on habitat suitability was examined under six SSP scenarios (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP4-6.0, SSP5-8.5).
In the North Sea, the projected impacts of climate change on the distribution of suitable habitats for Atlantic herring, Atlantic mackerel, and European seabass show notable trends under the SSP5-8.5 scenario. For Atlantic herring, habitat suitability is projected to decrease from an HSI of 1.00 in 2010 to 0.82 by 2100 due to changes in temperature. Similarly, Atlantic mackerel exhibits a decline in suitability from optimal habitat (HSI = 0.78) in 2010 to suboptimal (HSI = 0.56) by 2100. In contrast, European seabass maintains an HSI of 1.00 across all time periods. These results suggest a general resilience of European seabass to projected climate change impacts in the North Sea, whereas Atlantic herring and Atlantic mackerel may encounter more variable habitat conditions over the century.
The findings align with previous research showing latitudinal shifts in marine species due to warming temperatures, with significant implications for ecosystems and fisheries, particularly in the northern and southern regions of Europe. This underscores the necessity of adapting fisheries management to account for climate-induced shifts in pelagic fish distributions. As European fleets face new challenges posed by changing environmental conditions, this research provides crucial insights into future habitat suitability trends, aiding in the sustainable exploitation and conservation of these vital marine resources. Ultimately, this study highlights the importance of understanding shifts in fish habitat suitability to determine whether pelagic fisheries represent the future of the North Sea.
How to cite: Musimwa, R., Standaert, W., Stevens, M., Jesus Fernández Bejarano, S., Muñiz, C., Debusschere, E., Pint, S., and Everaert, G.: Navigating Climate and Policy Shifts: Habitat Suitability Modelling for North Sea Pelagic Fisheries in a Changing World , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21325, https://doi.org/10.5194/egusphere-egu25-21325, 2025.
Marine renewable energies are part of the current energy transition strategy in Europe. Offshore wind farms (OWFs) in the North Sea currently supply around 25.8 GW of power and are aimed to reach at least 117 GW by 2030. Yet, on its own, wind energy supply remains partially unreliable for a consistent energy generation. Offshore photovoltaic (PV) installations are increasingly considered a suitable technology to complement the intermittent energy supply of OWF. In the North Sea, installation of offshore photovoltaics within OWFs offers two significant advantages: (1) space optimization in an already busy North Sea, and (2) the possibility of utilizing and integrating an existing power network.
However, the installation of such systems comes with significant environmental challenges. In particular, solar technologies currently involve more submerged structures per produced energy unit. These floating structures induce hydrographic changes, particularly in terms of current velocity slowdown and turbulence production. Also, the floaters act as artificial hard substrates that are quickly colonized by organisms, potentially altering the biogeochemical dynamics of the water column and, ultimately, affecting the sediments.
This study provides a first assessment of the impact of PV structures on key hydrodynamic variables (e.g. current velocity fields, bottom shear stress, turbulence production), both in the near-field and far-field around an OWF using the 3D hydrodynamic model COHERENS (https://doi.org/10.5281/zenodo.11654795). A 3D computational grid around the Mermaid OWF in the Belgian part of the North Sea was implemented, with a grid resolution of 50m x 50m. We first present the impact of floating solar panels on the surrounding circulation and turbulence field, assessed using a sub-grid scale parameterization. Results from different scenarios will be presented and compared.
Second, we present a first estimate of the enrichment of organic carbon flux to the sediments due to the presence of colonizing organisms (mainly Mytilus edulis) on the submerged parts of PV structures. Our aim is to assess the areas of the seabed impacted by the deposition of faecal pellets due to the installation of PV structures within the OWF, considering the hydrodynamic perturbations presented above. This part uses a 3D Lagrangian particle tracking model (OSERIT; Dulière et al., 2012), faecal pellet characteristics gathered from laboratory experiments (e.g. sinking velocity, production rate and carbon content) and literature data on colonization of wind turbine foundations (Mavraki et al., 2020). In this model, each numerical particle represents a certain quantity of faecal pellets and, consequently, organic carbon.
Maps of faecal pellet deposition patterns will be presented for several scenarios of PV structures distribution in the Mermaid OWF. Our simulations show that the footprint affected by faecal pellet depositions could reach up to 18 times the surface area of the OWF and that the amount of carbon deposited could reach up to 1454 gC.km-² per day (worst-case scenario). These maps illustrate the causal relationship between PV farm design and the surface area of sediment affected by the faecal pellet deposition and thus exposed to organic carbon enrichment.
How to cite: Denis, P., Capet, A., Vanaverbeke, J., Ong, E. Z., Kerkhove, T., and Legrand, S.: Modelling the impacts of floating solar structures in a Belgian offshore wind farm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16328, https://doi.org/10.5194/egusphere-egu25-16328, 2025.
Due to its geographical location, the North Sea is one of the busiest seas worldwide, undergoing increasing pressure due to continuous developments of offshore human activities. These activities affect the North Sea ecosystem, for example by introducing new habitats/species or infrastructure into previously unobstructed environments. At the same time, climate change has already been affecting the North Sea ecosystem, leading to observed changes in species distribution. These changes may also affect physical processes such as stratification. Stratification is one of the main factors influencing primary production, which constitutes the foundation of the marine food web. To be able to mitigate these effects, it is crucial to understand the bottom-up, cumulative impacts of anthropogenic climate change and offshore activities on marine ecosystems. With this goal, we adapted and nested a 3D process-based hydrodynamics and water quality model of the North Sea (3D DCSM-FM) within a global Earth System Model (CMCC-ESM2). We simulated two contrasting future climate change scenarios: one representing the situation of a society focused on global sustainability, with low carbon emissions (SSP1-RCP2.6), and one of a society focused on global markets, with abundant exploitation of fossil-fuels and high carbon emissions (SSP5-RCP8.5). We investigated how the two different scenarios impact important abiotic and water quality variables, up to the end of the century.
As expected, our model results show clear surface water temperature increases for both scenarios, above 3°C by 2100. The Northern part of the North Sea is mainly driven by exchange with the Atlantic ocean. In the Northern and Eastern North Sea and in the Dogger Bank, our model simulates an increase in temperature stratification, leading to decreases in near-surface dissolved inorganic nutrient concentrations, chlorophyll-a and growing-season primary production (~-20-30% by 2100 on average in the Northern North Sea). The Southern part of the North Sea, especially along the coast, is driven by an along-coast current from the English channel and large, nutrient-rich freshwater inputs. The Southern North Sea shows a more spatially-variable response to the simulated scenarios in terms of nutrient concentrations, chlorophyll-a and primary production, with areas of increase and areas of decrease. Overall, the Southern North Sea shows a small increase in growing-season primary production for scenario SSP1-RCP2.6 by 2100 (+6%), while it shows a decrease for SSP5-RCP8.5 (-14%).
Our model offers the resolution to understand the effects of local pressures within a globally changing climate. Such tools are crucial to support the management of future offshore activities, ensure their long-term effectiveness and minimize their impacts on the ecosystem.
How to cite: Vilmin, L., Schneider, L., Heye, S., Zijl, F., Zijlker, T., Butenschön, M., Kristiansen, T., and van Duren, L.: Modelling bottom-up effects of climate change on primary production in the North Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16984, https://doi.org/10.5194/egusphere-egu25-16984, 2025.
Posters on site: Wed, 30 Apr, 14:00–15:45 | Hall X4
The impact of persistent anthropogenic activities on ecosystems remains a critical focus in the context of sustainability. Pollutants deposited into the ocean, alongside nutrients introduced via river discharge, are recognized as major sources influencing marine primary productivity. In particular, atmospheric pollutant emissions in East Asia have been continuously rising, and the resulting deposition of these pollutants into the ocean is estimated to be substantial. Despite their significance, quantitative assessments of the ecological and biogeochemical impacts remain largely unexplored. The excessive nitrogen deposition has the potential to accelerate eutrophication processes, leading to harmful algal blooms and subsequent oxygen depletion in the Yellow Sea. These phenomena are likely to significantly disrupt local biodiversity and marine food webs, posing challenges to sustainable ecosystem management. Furthermore, the reduction in atmospheric pollutants during the COVID-19 lockdown in 2020 has triggered discussions regarding its effects on the productivity of the Yellow Sea, reflecting the complex interactions between atmospheric deposition and marine ecosystems. Therefore, this study quantitatively evaluates the nitrogen flux introduced through atmospheric deposition and its influence on the marine ecosystem of the Yellow Sea using a numerical approach based on the Regional Ocean Modeling System (ROMS). Atmospheric pollutant data reproduced through deep learning served as input, enabling experiments ranging from one-dimensional vertical models to full-scale simulations of the entire Yellow Sea. The study was conducted using the NPZD (Nutrient-Phytoplankton-Zooplankton-Detritus) model framework.
How to cite: Kim, D., Choi, J.-G., Kang, E., Kwon, J.-I., Choi, J. Y., and Heo, K.-Y.: Quantifying the Role of Atmospheric Pollutant Deposition in Nutrient Flux of the Yellow Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14280, https://doi.org/10.5194/egusphere-egu25-14280, 2025.
Knowledge gaps in our understanding of processes that control transport and biogeochemical cycling of carbon in highly productive shelf seas like the North Sea restrict our ability to make accurate predictions of future environmental and climate change as shelf seas play a crucial role in global marine CO2 uptake and long-term storage. The NoSE project aims to tackle these knowledge gaps by constraining the past, present and future exchange of carbon and other essential nutrients in the Norwegian Trench (NT), the main outflow route of water from the North Sea to the Atlantic Ocean. In spring 2023, water samples were collected with a CTD-rosette on board the RV Pelagia along four transects to quantify and characterize pelagic fluxes of carbon and nitrogen associated with suspended particulate organic matter (SPOM) as well as dissolved organic matter (DOM).
First results reveal variations in SPOM and DOM throughout the NT that are related to the presence of two oceanic currents: the southward flowing Atlantic Inflow Water (AIW) characterized by high temperatures and salinity and the northward flowing Norwegian Coastal Current (NCC) characterized by low temperatures and low salinity. DOC concentrations in the AIW and NCC range between approximately 53 to ±80 µM and ±70-128 µM, respectively. Surface POC concentrations vary between 0.04-0.20 mg/L in the AIW and 0.06-0.23 mg/L in the NCC. Moreover, the δ13C, δ15N and C:N signatures of the surface mixed-layer SPOM samples show increased trophic complexity and decreased bio-availability in the NCC. Likely, these two major currents in the NT are paralleled by distinct changes in Biological Carbon Pump regime, with different plankton communities, export fluxes and mechanisms. These results will allow for the determination of organic carbon export efficiencies and overall organic carbon fluxes throughout the NT.
How to cite: Temmerman, D., Mienis, F., Middag, R., and Reichart, G.-J.: Concentrations and composition of suspended particulate organic matter suggest distinct biological carbon pump regimes in Norwegian Trench waters., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15157, https://doi.org/10.5194/egusphere-egu25-15157, 2025.
Most of the studies on the ecology and biogeochemistry of the ocean have focused on bacteria, arachae and protists, whereas pelagic fungi have been less studied. However, recent studies have revealed that pelagic fungi are ubiquitously found throughout the water column in every ocean basin, and actively involved in the degradation of organic matter and nutrient fluxes. Yet their quantitative contribution to carbon stocks remains elusive and we are missing data from polar waters despite being among the most vulnerable regions to climate change. Here, we present novel insights into the biomass distribution of pelagic fungi and employ metagenomic and metatranscriptomic approaches to investigate their role in organic matter degradation across polar and non-polar waters. Globally, fungi account for approximately 0.32 Gt C, surpassing archaea (Archaea:Fungi:Bacteria biomass ratio of 1:9:44). Functional and taxonomic analyses reveal distinct adaptations between polar and non-polar regions: fungi in polar waters show a preference for protein-rich substrates, while those in non-polar regions exhibit increased carbohydrate degradation. This functional specialization is further reflected in niche partitioning in non-polar waters, with Basidiomycota dominating protein degradation in larger size fractions and Chytridiomycota being more active in smaller fractions. These dynamics suggest a strong link between fungal functionality and environmental conditions shaped by anthropogenic influences. As warming temperatures and changing ocean conditions intensify, the shifting functional roles of pelagic fungi could drive profound changes in nutrient cycling. By advancing our understanding of fungal biomass distribution, and phylogenetic and functional diversity, this study underscores the urgent need to consider pelagic fungi in assessing the impacts of anthropogenic change on marine biogeochemical cycles.
How to cite: Breyer, E., Guo, K., Zhao, Z., and Baltar, F.: Pelagic fungi as key players in marine ecosystems: Implications for a warming Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2218, https://doi.org/10.5194/egusphere-egu25-2218, 2025.
The Yeosu Coast, a region of critical ecological and economic importance on the Korean Peninsula, has experienced significant changes in fish community dynamics over recent decades. This study provides a comprehensive analysis of daily set-net catch data collected from 2008 to 2023 (excluding 2017) to investigate long-term shifts in species composition and community structure. The findings indicate a dominance of warm-water species, reflecting the region’s temperate to subtropical marine environment. During the study period, the total catch amounted to 3,501.9 tonnes, with the highest annual catch recorded in 2010 and the lowest in 2016. Species composition changes were strongly correlated with sea surface temperature, identified as the primary environmental driver of these dynamics. The dominant species, Scomberomorus niphonius (Cuvier, 1832) and Engraulis japonicus (Temminck & Schlegel, 1846), together accounted for 77.4% of the total biomass. Biodiversity trends, measured using the Shannon–Weaver diversity index, revealed a marked decline in 2015 compared to 2008, highlighting significant alterations in community structure. Furthermore, the study emphasizes the compounded threats of climate change and the increasing prevalence of jellyfish blooms, which pose serious challenges to fishery productivity and biodiversity. These results underscore the urgent need for targeted management strategies and sustained monitoring to ensure the long-term sustainability of fisheries in this region amidst ongoing environmental changes.
How to cite: Moon, S. Y., Choi, H., and Jung, K. M.: Long-term dynamics of fish communities: A 16-years study in the Yeosu Coast, Korea , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18762, https://doi.org/10.5194/egusphere-egu25-18762, 2025.
Under the multiple stressors of global climate change and extensive human activities, costal ecosystems are under major threats. Degradation of marine ecosystems will lead to pronounced impacts on their functions. The sustainable development of coastal areas faces serious challenges. Microplastic contamination is a growing threat to marine environment and biota, and represent a great risk for marine ecosystems, society and human health. To help design effective plastic reduction and mitigation strategies, cognition of distribution and characteristics of plastic pollution in multiple matrices are required. We took Jiaozhou Bay as a typical area in coast of China, revealed distribution and characteristics of microplastics in multiple matrices, and the emission characteristics of microplastic sources. An index MCI (microplastic complexity index) was used that is to reflect the contrast of microplastics complexity in different matrices. It can be used for quantitative analysis of microplastic traceability process. and provides new ideas for source apportionment and ecological assessment of microplastics. Quantitative source apportionment is continuing to further promote the accomplishment of goal 14.1 in SDGs and decision support.
How to cite: Zheng, S.: Characteristics of microplastics in different matrices in Jiaozhou Bay, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9844, https://doi.org/10.5194/egusphere-egu25-9844, 2025.
Microplastics, as an increasingly concerning environmental pollutant, transport from the surface waters to the seafloor after entering the ocean and can be buried in deeper sediments through bioturbation. However, the role of marine organisms in this vertical transport remains unclear. In this study, sediment traps were used to quantify the contribution of typical filter-feeding organisms, including sea squirts (Halocynthia roretzi), Pacific oysters (Crassostrea gigas), scallops (Chlamys farreri), and Manila clams (Ruditapes philippinarum), to the vertical transport of microplastics in the water column. The results showed that microplastics were present in feces and pseudofeces of filter-feeding organisms and sank to form biodeposits, significantly enhancing the deposition of microplastics <1000 μm in size and with positive buoyancy (density lower than seawater). Additionally, experiments with Manila clams, a representative benthic filter-feeding species, were conducted to simulate bioturbation processes in sediments. The results demonstrated that exposure to polystyrene microbeads did not significantly affect the physiological indices of clams. The burrowing, movement, and feeding activities of clams facilitated the rapid transport of microplastics to deeper sediment layers (6–8 cm below the surface). These findings highlight the critical role of filter-feeding organisms in the vertical transport of microplastics in the water column and sediments, contributing to a better understanding of microplastic spatial variability and source-sink dynamics.
How to cite: Sun, X.: Vertical transport of marine microplastics mediated by filter-feeding organisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9718, https://doi.org/10.5194/egusphere-egu25-9718, 2025.
Coastal marine ecosystems are significantly affected by human activities along the coast and continental shelf. Innovative monitoring techniques, including autonomous platforms and advanced multimetric habitat quality indices, offer new ways to understand these ecosystems' responses and help prevent habitat degradation.
We evaluated the habitat quality and the transition from coast to offshore of benthic habitats in three coastal areas of the northeastern Tyrrhenian Sea (Italy). Our approach combined autonomous technologies, such as an Unmanned Surface Vehicle (USV) and Remote Operated Vehicle (ROV), alongside multimetric habitat quality indices.
The findings revealed moderate habitat quality across the study sites and demonstrated the effectiveness of this methodology for broader application, particularly in areas with diverse seabeds. This approach also has the potential to improve numerical models and Digital Twins of the Oceans (DTOs), offering high-resolution and near real-time data on habitat quality.
How to cite: Piazzolla, D., Bonamano, S., Penna, M., Resnati, A., Scanu, S., Madonia, N., Madonia, A., Fersini, G., Coppini, G., Marcelli, M., and Piermattei, V.: Advanced Surveying Methods and Multimetric Indices for Evaluating Coastal Benthic Habitat Quality in the Northeastern Tyrrhenian Sea (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3133, https://doi.org/10.5194/egusphere-egu25-3133, 2025.
According to the IPCC (2022), climatic phenomena such as increased wind stress and nighttime heat loss influence the depth of the mixed layer and, consequently, pelagic primary production. The use of Gliders, an autonomous underwater vehicle, represents a promising method for investigating the interaction between chlorophyll biomass, oceanographic processes, and climatic phenomena, with significant implications for understanding marine ecosystems, secondary production, and their implication on economic activities.
Gliders are advanced tools for oceanographic data collection, particularly useful for studies conducted over long distances and extended periods. Thanks to their ability to operate both vertically and horizontally, Gliders can also be programmed to monitor specific sites over time, enabling detailed analysis of complex oceanographic phenomena.
In this study a Glider was used to investigate the Tiber River plume and its effects on the waters of the Tyrrhenian shelf.
The data collected revealed important oceanographic features, including the position of the Deep Chlorophyll Maximum (DCM), which was shallower near the coast and deeper toward the open sea. This phenomenon is linked to high surface temperatures and the formation of a pronounced mixed layer, which pushes phytoplankton toward the bottom of the water column. Furthermore, the analysis of the sections highlighted a well-defined thermocline and halocline throughout the area, while the Tiber plume predominantly influenced the first 500 m of the transect, reducing salinity and increasing the surface concentration of chlorophyll a and turbidity.
This study shows the preliminary results of the effectiveness of Gliders in investigating river plumes and oceanographic phenomena at both coastal and mesoscale levels. Their ability to collect data at high spatial and temporal resolutions makes them invaluable tools for future applications, including primary production and numerical modeling.
How to cite: Torelli, B. and Marcelli, M.: Glider and Oceanographic Processes: A high-resolution analysis of the Tiber river plume, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11738, https://doi.org/10.5194/egusphere-egu25-11738, 2025.
The North Sea helps mitigate the impact of human activities on Earth’s climate by absorbing carbon dioxide (CO2) out of the atmosphere. However, the fate of the absorbed CO2 is poorly constrained: 0-40 % is estimated to be stored in seafloor sediments as organic matter, with the remaining 60-100 % transported by ocean currents out into the Atlantic Ocean. For the latter portion, the depth at which North Sea waters are exported controls the timescale on which the CO2 is stored, with deeper export constituting a more enduring carbon sink. During a NoSE (North Sea-Atlantic Exchange) project expedition in spring 2024, a season when biological productivity drives high CO2 uptake, we deployed two ocean gliders in the Norwegian trench, the main conduit for water exchange between the North Sea and Atlantic Ocean, for several weeks. These autonomous underwater vehicles carried sensors to characterise the water mass structure and some key biogeochemical properties for carbon export (e.g., dissolved oxygen). Here, we use these sensor data together with a broader set of water column observations collected during a concurrent research cruise (including nutrients and marine carbonate system parameters) to investigate potential carbon export mechanisms. The trench was vertically stratified with a deep layer containing extra CO2 that was being transported towards the Atlantic Ocean. However, the stratification was due to relatively warm, salty North Sea waters being trapped beneath a surface layer of colder, fresher waters from the Norwegian fjords. As this surface layer is spatially confined near the coast, rather than extending widely across the Atlantic, the deeper layer might be exposed to the surface soon after exiting the Trench, and thus its extra CO2 returned to the atmosphere where it can affect Earth’s climate.
How to cite: Mienis, F., Brandon, M., Adler, M., and Humphreys, M.: The Norwegian Trench as a carbon conduit from the North Sea to the deep Atlantic Ocean: insights from ocean glider observations in spring 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10854, https://doi.org/10.5194/egusphere-egu25-10854, 2025.
Marine coastal ecosystems play a vital role in carbon storage and sequestration, making a significant contribution to climate change mitigation. However, their accessibility and location in shallow coastal waters make them particularly vulnerable to human activities such as habitat destruction and water pollution. While recent estimates of ecosystem services have been conducted in some Italian regions, spatially explicit research on the blue carbon potential of Posidonia oceanica remains limited.
This study analyzed carbon sequestration using a spatially explicit approach, employing various modeling methods in line with the tiered framework proposed by the IPCC. Among the most promising tools, the InVEST Coastal Blue Carbon (InVEST CBC) model (https://naturalcapitalproject.stanford.edu/invest/) was applied to quantify carbon dynamics in coastal and marine ecosystems under present conditions and future scenarios. The model evaluated pressures contributing to carbon emissions and accumulation over time, providing spatially detailed outputs in raster format.
The InVEST CBC model was informed by:
- The spatial distribution of Posidonia oceanica in Italian coastal waters, recently updated by ISPRA as part of the implementation of the Marine Strategy Framework Directive.
- Ecological parameters of Posidonia oceanica (e.g., distribution, density, foliar and rhizome production, and ecological status) derived from field data and existing literature.
- Maps of current pressures affecting carbon storage, such as boat anchoring, coastal engineering, aquaculture, urban effluents, land use, coastal population density, and fishing activities in Italian coastal areas.
The study evaluated blue carbon sequestration under three future scenarios:
- Business-as-usual: Assumed no significant improvements in environmental factors, maintaining current levels of human impacts that contribute to meadow regression.
- Sustainable future: Envisioned significant reductions in anthropogenic pressures compared to the business-as-usual scenario, promoting the conservation of seagrasses by 2050. This scenario also examined the role of sustainable mooring systems in mitigating anchoring impacts from recreational boating.
- Non-sustainable future: Projected increased human pressures, resulting in significant losses of seagrasses compared to the business-as-usual scenario by 2050.
The sustainable future scenario was specifically assessed in marine protected areas, including the Archipelago of La Maddalena National Park, Asinara National Park, and Cilento, Vallo di Diano e Alburni National Park. In these areas, state-of-the-art mooring fields were implemented as part of the Sea Forest Life project (LIFE17 CCM/IT/000121; https://www.seaforestlife.eu/en/).
How to cite: Bonamano, S., De Luca, A., Pulcini, M., Maltese, S., Bellotta, M., Madonia, A., Miozzo, M., and Scardi, M.: Future Scenarios of Blue Carbon Sequestration inItalian Posidonia oceanica Meadows, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10978, https://doi.org/10.5194/egusphere-egu25-10978, 2025.
Deep-sea habitat-forming species face increasing threats from human activities, particularly destructive fishing practices and the effects of anthropogenic climate change. These species are now classified as Vulnerable Marine Ecosystems (VMEs), due to their slow growth rates and limited capacity for recovery after disturbance. VMEs are vital indicators of deep-sea biodiversity, and they often correlate with the presence of commercially important fish and other marine species.
Given the logistical challenges of deep-sea mapping, habitat suitability modelling (HSM) can offer critical insights into VMEs’ distributions. This research employs HSM to estimate the current distributions of a number of VMEs in the North-East Atlantic using an ensemble of three methodologies: Maximum Entropy (Maxent), Generalised Additive Models (GAM), and Random Forest. In addition to modelling current distributions, projections under future climate conditions were produced for a range of Shared Socioeconomic Pathways (SSP) scenarios, incorporating six IPCC climate projections over 10 decades using high-resolution environmental data. These analyses will help assess climate velocities and identify climate refugia for VMEs under a wide range of potential future conditions. The findings will also inform decision-making by highlighting priority areas for biodiversity conservation, supporting the designation of new Marine Protected Areas (MPAs) in the Irish Exclusive Economic Zone (EEZ) and wider North-East Atlantic.
How to cite: Segato Monteiro, B., Grehan, A., and Callery, O.: Forecasting the Impacts of Climate Change on the Distribution of Vulnerable Marine Ecosystems (VMEs) in the North-East Atlantic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14228, https://doi.org/10.5194/egusphere-egu25-14228, 2025.
The global ocean comprises – together with the terrestrial biosphere – the most significant sink for man-made carbon dioxide (CO2). It is estimated that 10-15% of the annual marine net CO2 uptake CO2 occurs in coastal seas. however, for most coastal regions, the exchange of CO2 at the air-sea interface and its temporal variation are to-date insufficiently constrained by observations and not fully introduced in global and regional carbon budgets. This is largely due to the complexity of the processes at play and the resulting spatial heterogeneity of CO2 source and sink regions that require a dense network of measurements that is currently missing in most ocean regions. Better understanding of the regional air-sea CO2 dynamics is crucial to assess the effect of human activities, understanding the impact of extreme events, and monitoring the success of emission reductions.
Besides being a significant element of the carbon cycle, coastal seas are heavily impacted by human activities and increasingly used to test and implement marine carbon dioxide removal (mCDR) approaches, which require reliable observations to support their monitoring, reporting, and verification (MRV). The Belgian part of the North Sea offers a unique site to test the requirements and design of a fit-for-purpose monitoring system; the Belgian coast is among the densest observed coastal regions for CO2, largely due to a combination of its small size and the intense monitoring efforts.
Through the VLAIO-funded BERNARDO project, we intensify our monitoring activities in the Belgian Part of the North Sea and build a contemporary coastal carbon budget that can serve as a present-day baseline to monitor effects of human activities and climate extremes. We expanded the ICOS observing network with ship-based biogeochemical parameters, new sampling platforms, such as Uncrewed Surface Vehicles (USVs), remote sensing data, and machine learning reconstructions to monitor the exchange of CO2 at the air-sea interface and its redistribution at the Belgian Part of the North Sea and provide spatially explicit maps at kilometer spatial and daily temporal scale.
Together with industry partners, we propose use cases to test whether our monitoring system is capable of detecting and attributing carbon emissions from common human activities taking place in the Belgian part of the North Sea such as aquaculture, bottom disturbing or CO2 uptake enhancing activities. The project will thus inform about Marine Spatial Planning requirements that can be adopted to benefit net air-sea CO2 exchange. Additionally, the high-resolution nature of the carbon maps allows to better understand the effects of extreme events, such as marine heat waves on the coastal carbonate system.
How to cite: Landschützer, P., Roobaert, A., Keppens, M., van Langen Rosón, A., Boone, W., Ponsoni, L., Gkritzalis, T., Pirlet, H., Dauwe, S., Lemey, E., Herremans, B., Goyens, C., and Neukermans, G.: The Belgian Part of the North Sea as a test case to monitor human activities and climate change effects on the coastal carbon system, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15911, https://doi.org/10.5194/egusphere-egu25-15911, 2025.
The hadal trenches, with depths exceeding 6,000 meters, are critical yet understudied sinks for anthropogenic pollutants. However, advances in deep-sea technology and growing interest in ocean health drive the need for new tools to study deep-sea sediments. This study explores the prevalence and impact of organic and inorganic contaminants in the Japan Trench hadal sediments, focusing on their origins, pathways, preservation and potential ecological consequences. Sediment samples were collected from water depths of 7,000–7,800 meters in the hadal zones during IODP Exp. 386. The samples were analyzed through a multidisciplinary approach, incorporating oceanography, analytical biogeochemistry, and statistical analysis. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed concentrations of persistent organic pollutants (POPs) ranging from µg to ng/g, including polycyclic aromatic hydrocarbons (PAHs), dichlorodiphenyltrichloroethane (DDT), and its metabolites (DDX). Sequential extraction and microwave-assisted digestion techniques quantified heavy metals and metalloids bound to sediment matrices, emphasizing the accumulation of inorganic pollutants, such as Pb, Zn, Te, As, Cd, Ni. Total Organic Carbon (TOC) and biomarkers analyses (e.g., n-alkanes) were performed to determine the primary sediment transport pathways delivering pollutants into the trench. The results, interpreted through statistical analyses of correlations between pollutant concentrations, biomarkers, biogeochemical factors (e.g., TAR, CPI ratios), and sediment accumulation rates, reveal a complex interplay between terrestrial and marine sediment sources. Oceanic processes and seismic events contribute to pollutant transport and deposition in deep-sea trenches, which act as global contaminant sinks, with pollutants transported via marine snow, seismic-induced sediment remobilization, and tsunami backwash, posing risks to fragile hadal ecosystems. By identifying biomarkers and pollutant assemblages, this study quantifies transport processes and offers valuable insights into sedimentary pollution history, its impact on biogeochemical cycles, and its consequences for marine biodiversity and ecosystem functions. The findings highlight the significant influence of both human activities and natural processes on the ocean's deepest regions, stressing the need for interdisciplinary strategies to better understand sediment-associated transport processes, as well as the fate and toxicological potential of persistent pollutants in the least studied environments on Earth – the hadal deep-sea basins.
How to cite: Trotta, S., Bellanova, P., and Schwarzbauer, J.: Anthropogenic Shadows in the Earth's Deepest Environments: Insights into Hadal Zone Pollution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18121, https://doi.org/10.5194/egusphere-egu25-18121, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot 4
EGU25-7292 | ECS | Posters virtual | VPS18
Primary producers as indicators of anthropogenic intervention in the Colombian PacificWed, 30 Apr, 14:00–15:45 (CEST) vPoster spot 4 | vP4.12
The coastal ecosystems, including estuaries and mangroves, are highly vulnerable to anthropogenic intervention, particularly due to activities such as urbanization, wastewater discharge, and industrial development, which can alter their ecosystem services and affect habitat quality. In order to evaluate the impact of these interventions through the carbon and nitrogen isotopic composition of two macroalgae Boodleopsis verticillata and Bostrychia spp in four coastal ecosystems of the Colombian Pacific (Valencia - VAL, San Pedro - SPE, Chucheros – CHU with low intervention, and Piangüita - PIA with high intervention) were used to understand the sources of these elements. δ15N values is a commonly used to providing information about nitrogen sources in primary producers. δ13C values is used to investigate carbon sources i.e. terrestrial or marine. Samples were collected during 2014, 2015, and 2016, and analyzed by isotope ratio mass spectrometer. The results show that the δ13C values ranged from -33.97 to -31.93 ‰ in VAL, -33.78 to -30.09 ‰ in SPE, -31.12 to -28.45 ‰ in CHU, and -33.32 to -21.71 ‰ in PIA. δ15N values ranged from 0.32 to 3.18 ‰ in VAL, 0.57 to 5.47 ‰ in SPE, 1.82 to 3.39 ‰ in CHU, and 2.32 to 10.16 ‰ in PIA. Significant differences were found among the four areas with mean δ13C values by locality (VAL -30.21 ‰, SPE -31.71 ‰, CHU -30.09 ‰, and PIA -30.52 ‰) and δ15N values (VAL 1.74 ‰, SPE 2.30 ‰, CHU 2.40 ‰, and PIA 4.47 ‰) reflecting the impacts of human activities on the coastal ecosystems. This work contributes to understanding the effects of anthropogenic intervention on pollution and wastewater discharge in coastal ecosystems, providing key tools for the development of environmental management policies that support conservation in the Colombian Pacific.
How to cite: Arce-Sánchez, R. S., Medina-Contreras, D., and Sánchez-Gonzalez, A.: Primary producers as indicators of anthropogenic intervention in the Colombian Pacific, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7292, https://doi.org/10.5194/egusphere-egu25-7292, 2025.
