ITS5.12/CL0.1.11 | Interdisciplinary approaches to understanding processes in coastal regions and nature-based solutions
Interdisciplinary approaches to understanding processes in coastal regions and nature-based solutions
Convener: Maren Voss | Co-conveners: Marcus Reckermann, Timothy Stojanovic, Eleonora GioiaECSECS, Fereidoun Rezanezhad, Sara E. Anthony, Eva EhrnstenECSECS
| Wed, 17 Apr, 16:15–18:00 (CEST)
Room 2.24
Posters on site
| Attendance Wed, 17 Apr, 10:45–12:30 (CEST) | Display Wed, 17 Apr, 08:30–12:30
Hall X5
Posters virtual
| Attendance Wed, 17 Apr, 14:00–15:45 (CEST) | Display Wed, 17 Apr, 08:30–18:00
vHall X5
Orals |
Wed, 16:15
Wed, 10:45
Wed, 14:00
Coastal zones are of high ecological and recreational value. At the same time, they are heavily impacted by a combination of natural and anthropogenic drivers of change, such as drainage, nutrient pollution, land use and fishing. This interdisciplinary session combines studies of the interrelationship of climate and other drivers of change on coastal processes (former ITS5.12), including biogeochemical cycling (former BG4.3), and nature-based solutions to manage these coastal socio-ecological systems (former ITS4.7).

Orals: Wed, 17 Apr | Room 2.24

Chairpersons: Maren Voss, Timothy Stojanovic, Marcus Reckermann
Virtual presentation
Caroline P. Slomp

Coastal waters worldwide are increasingly affected by oxygen loss due to human-induced eutrophication and global warming. This coastal deoxygenation has dramatically altered biogeochemical processes with major consequences for marine life. Prominent examples of large anthropogenic coastal “dead zones” include the Gulf of Mexico, Baltic Sea and Chesapeake Bay but numerous small coastal systems are also strongly affected. Many efforts are currently underway to restore the water quality of these coastal waters, but these are not always effective. In this presentation, I will discuss how the interplay of biogeochemical processes and hydrodynamics may affect present-day restoration efforts in coastal systems. Using examples from a range of field and modelling studies performed by my group, I will specifically discuss legacy effects resulting from accumulation of organic-rich sediments, the potential for reoxygenation of coastal waters through increased water column mixing and/or lateral water exchange and the expected short-term and long-term effects of nutrient load reductions. Taken together, our results highlight that there is no one-size-fits-all approach to rapidly improve water quality in coastal waters suffering from eutrophication and deoxygenation.


How to cite: Slomp, C. P.: Eutrophication and deoxygenation of coastal waters: how to improve water quality? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12502,, 2024.

On-site presentation
Ziyan Wang and Benoit Thibodeau

Rapid population growth and intensification of human activities have led to a massive increase in the release of nitrogen (N) to the environment, often ending up in aquatic ecosystems. Coastal wetlands, a transition ecosystem in the freshwater-to-marine continuum, play a vital role in reducing nitrogen through natural processes, including denitrification and anaerobic ammonium oxidation (anammox). Considering denitrification's risk of producing nitrous oxide—a potent greenhouse gas—and anammox's efficient co-removal of ammonium and nitrite, it's crucial to identify what controls the balance between these two key processes. However, the identity of the drivers controlling the relative abundance of these two N-removal processes and their respective interactions with carbon (C) and sulfur cycles are not well-documented, especially in coastal wetlands.

This study investigated salinity's role in N reduction with carbon remineralization in coastal wetlands facing salinity intrusion. Using air-dried mangrove sediments mixed with anoxic artificial seawater of contrasting salinities (0, 10, 20, and 30 ppt) over a 28-day period, we monitored N and C transformation by the concentration of NH4+, NO2-, NO3-, dissolved inorganic carbon (DIC) and total alkalinity in the supernatant, and microbial community adaptation in sediment by molecular analysis. We applied the revised 15N-paring isotope technique in slurry incubation to quantify the potential of N loss pathways.

Preliminary results indicate that significant N removal starts after a week of internal cycling between organic and inorganic N, with the maximum removal potential at 30 ppt salinity. Depletion of NO3- in the last week of incubation makes anammox stand out by utilizing NH4+ and NO2-. The rate of DIC release decreased with increasing salinity, displaying an inverse pattern to that of N species. This decoupling points to the co-existence of autotrophic anammox, heterotrophic denitrification, and sulfate reduction processes. The stoichiometric ratio of total alkalinity to DIC suggests a shift of the predominant carbon decomposition process as salinity increased, from denitrification to sulfate reduction. This shift could enhance the total nitrogen removal potential while slowing carbon remineralization, indicating a positive feedback loop for both nitrogen removal and blue carbon storage in response to salinity intrusion. We will further focus on 15N2 samples and microbial evidence to elucidate the interplay among nitrogen removal processes.

How to cite: Wang, Z. and Thibodeau, B.: Nitrogen removal and carbon mineralization under coastal salinity intrusion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-493,, 2024.

Virtual presentation
Cordula Gutekunst, Susanne Liebner, Anna-Kathrina Jenner, Erwin Don Racasa, Klaus-Holger Knorr, Sara E. Anthony, Daniel Lars Pönisch, Michael Ernst Böttcher, Manon Janssen, Jens Kallmeyer, Franziska Koebsch, Gregor Rehder, and Gerald Jurasinski

Around 4 % of global greenhouse gas (GHG) emissions originate from drained peatlands. Unlike rewetting drained peatlands with freshwater, brackish water rewetting of coastal peatlands might not only reduce CO2 emissions, but also keep methane (CH4) emissions low. The re-establishment of the natural brackish water regime of coastal peatlands with high sulfate levels should favor sulfate reducing bacteria as well as sulfate-driven anaerobic methane oxidizers and therefore limit CH4 production and/or lead to increased CH4 consumption. Here, we compared CO2 and CH4 fluxes, pore water geochemistry, and associated microbial communities of a coastal fen along a moisture gradient before, and a water level gradient after rewetting.

Brackish water rewetting increased the abundances of CH4 producing archaea (methanogens) as well as the abundances of sulfate reducing bacteria (SRB) in most of the study site, except at former ditch areas, where methanogenic and SRB abundances had been high before. At the same time, the aerobic methanotroph community was less present, indicating lower aerobic CH4 oxidation potentials after rewetting. Pore water CH4 and CO2 concentrations along with δ13C records suggest that both, methanogenesis and CH4 oxidation, increased after rewetting. Brackish water rewetting raised average CH4 emissions from 2 to 25 mg CH4 m-2 d-1 at locations that were previously drained, which is lower than CH4 emissions reported from most freshwater peatlands. Net CO2 emissions remained high after rewetting with values around 4 g CO2 m-2 d-1. However, since ecosystem respiration strongly decreased from on average 19 to 6 g CO2 m-2 d-1, the remaining net CO2 emissions were mostly associated with low CO2 uptake due to extensive die-back of the vegetation. Hence, brackish water rewetting can keep CH4 emissions relatively low, but, as in freshwater peatlands, hydrological management must allow for the re-establishment of site-specific vegetation to sustain net CO2 uptake.

How to cite: Gutekunst, C., Liebner, S., Jenner, A.-K., Racasa, E. D., Knorr, K.-H., Anthony, S. E., Pönisch, D. L., Böttcher, M. E., Janssen, M., Kallmeyer, J., Koebsch, F., Rehder, G., and Jurasinski, G.: Brackish water rewetting of a temperate coastal peatland: Effects on biogeochemistry, microorganisms and greenhouse gas emissions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12654,, 2024.

On-site presentation
Teresa Radziejewska, Brygida Wawrzyniak-Wydrowska, and Bartosz Bieniek

Construction of coastal infrastructure, e.g. seaward port facilities, frequently calls for sediment removal (dredging). Deposition of the dredging spoil at designated offshore sites (dumping grounds) disturbs the dumping ground sedimentary system, including the biota. Assessment of environmental effects of dumping requires monitoring of the system’s responses to the disturbance severity and persistence. In 2011-2017, we followed changes in sediment characteristics and descriptors of benthic (meio- and macrofaunal) assemblages (abundance, biomass, composition) in a shallow southern Baltic coastal area serving as a dumping site for dredging waste from a new harbour under construction at the coast. At the initial phase of the disturbance, the benthos responded rapidly (abundance and biomass reduction, altered composition), and equally rapidly recovered when dumping was temporarily suspended. After the dumping operations were resumed, the responses intensified, although apparent colonizers (benthic copepods in the meiobenthos and juvenile molluscs in the macrobenthos) tended to appear intermittently in the disturbed areas. The benthos remained impoverished in the altered habitat after dumping was terminated, reflecting the severity of habitat change.

How to cite: Radziejewska, T., Wawrzyniak-Wydrowska, B., and Bieniek, B.: A human driver of change in the southern Baltic coastal sedimentary system: monitoring effects of dredging spoil dumping on benthic communities , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3213,, 2024.

On-site presentation
Nur Sakinah Abdul Razak, Yang Shouye, Hasrizal Shaari, Vasquez Ana Cristina, Guo Junjie, and Wu Xuechao

The interaction between land and sea in the coastal zone is dynamic and highly sensitive. It not only records past transgression history, coastal environmental evolution, and sea level changes, but also provides information on climate fluctuations, ocean and river changes, ecological environmental evolution, and human-induced environmental impacts. Coastal zone deposition plays a crucial role in preserving records of paleoenvironment changes and is therefore a key component larger ‘source to sink’ systems at continental margin. Therefore, it has attracted great academic interest in the field of geoscience in recent years. In this study, we measured trace elements and rare earth elements (REEs) in 20 surface sediment samples and a core (LKC 2) collected from the coastal lagoon of Sungai Kilim, Langkawi, Malaysia, to determine the possible sources and to reveal the variations in response to climate change and human activities. The distribution of trace elements (e.g., Li, Ti, Cr, Co, Ni, Cu, Zn, and Mn) was enriched in surface sediments, indicating those elements are affected by human activities. Besides, the concentrations of trace element in LKC 2, combined with AMS dating further confirmed the anthropogenic provenance in the uppermost core layers as a result of deforestation and urbanization in recent decades. However, the low Rb/Sr ratios in surface sediments and LKC 2 corresponds to higher intensity chemical weathering, resulting in higher concentrations of dissolved Sr in the sediments. The enrichment of REEs in surface sediments and LKC 2 indicates typical minerals present in the study area. Overall, the elemental flux patterns observed in this study are responses to complex interactions between intensified human activities and natural climate variability.

How to cite: Abdul Razak, N. S., Shouye, Y., Shaari, H., Ana Cristina, V., Junjie, G., and Xuechao, W.: Geochemistry of tropical coastal lagoon sediments from Sungai Kilim, Langkawi, Malaysia: Implications for provenance and weathering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18677,, 2024.

On-site presentation
Veronika Mohr, Wenyan Zhang, Corinna Schrum, and Tobias Dolch

Seagrass is regarded with great expectations when it comes to nature-based coastal protection measures. Seagrass meadows dampen waves, reduce currents, and stabilize sediments in the coastal environment. However, most modeling studies estimating the magnitude of the coastal protection effect by seagrass assume a constant seagrass cover throughout the year. In temperate climates such as Northern and Central Europe the seagrass cover has considerable annual and interannual variations. The seagrass cover is highest in late summer and autumn and lowest in winter and early spring. At the same time, the physical forcing of waves and currents is at its maximum in winter, indicating a discrepancy between the seasons with the highest benefits of seagrass to coastal protection and the seasons with the most threat to the stability of the coast. In this study, we use a 3D baroclinic circulation model (SCHISM) coupled with a sediment model and a model of seagrass growth dynamics for estimating the significance of seasonality for coastal protection. A case study of a tidal basin in the northern Wadden Sea indicates that disregarding the seasonality can lead to substantial overestimations of the effectivity of seagrass for coastal protection.

How to cite: Mohr, V., Zhang, W., Schrum, C., and Dolch, T.: The importance of Seasonality for Seagrass as Coastal Protection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19197,, 2024.

On-site presentation
Gaurav Savant

Nearshore strategic placement—in addition to direct placement—has been proposed as a nature-based solution to reuse dredged sediment in support of mitigating the effects of sea level rise in the San Francisco Bay Area. The success of nearshore strategic placement relies on hydrodynamic forces moving sediment from the placement site to mudflats and marshes over time. Sediment transport and pathway models can be used to evaluate and prioritize potential placement sites, placement methods, transport rates (informing amount and frequency of sediment placement), sediment fate, and longevity. Models can also be used to predict the evolution of sites after initial placement and as sea level and sediment supply conditions evolve. This model-based information is needed to design wetland restoration and maintenance operations, inform the permitting approval process, and evaluate the costs and benefits of using strategic placement techniques to restore and maintain Bayland habitats in San Francisco Bay. This talk will focus on the estuarine process modeling as well as in-situ observation efforts that are being undertaken to assess sediment fate, sediment transport rates and sediment transport dynamics associated with nearshore strategic placement.

How to cite: Savant, G.: Modeling the San Francisco Bay Estuary to Inform Nature-Based Sediment and Baylands Management , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13084,, 2024.

On-site presentation
George Zittis, Shiri Zemah-Shamir, Mirela Tase, Savvas Zotos, Nazli Demirel, Christos Zoumides, Tamer Albayrak, Cigdem Kaptan Ayhan, Irene Christoforidi, Turgay Dindaroglu, Mauro Fois, Paraskevi Manolaki, Attila Sandor, Ina Sieber, Stamatiadou Valentini, Elli Tzirkalli, Ioannis Vogiatzakis, Ziv Zemah-Shamir, and Aristides Moustakas

Islands are hotspots of biological and cultural diversity, which, compared to mainlands, are more vulnerable to environmental degradation, climate change, uncontrolled land use changes and financial or societal crises. Particularly when combined, these factors can increasingly impact the environmental and socioeconomic services in many of such isolated ecosystems and communities. Atmospheric warming, ocean acidification or other abrupt climate changes can directly impact the biodiversity of islands and surrounding water bodies, the associated Ecosystem Services and, in turn, the well-being of islanders. Although existing techniques can adequately predict climate-induced ecological changes over the continents or in the larger islands, this is not the case for smaller islands, where refined climate information is typically not available. The primary objective of the present review is to better understand the linkages between Ecosystem Services and climate change on islands from the global to regional and local scales. This is not limited to the direct positive or negative impacts of changes in environmental and climate conditions but also includes the potential of ecosystem services to provide nature-based solutions for climate change mitigation and adaptation. Non-climatic drivers, e.g., land use changes, that may augment or alleviate the effects of climate change on islands’ Ecosystem Services are also explored.

How to cite: Zittis, G., Zemah-Shamir, S., Tase, M., Zotos, S., Demirel, N., Zoumides, C., Albayrak, T., Kaptan Ayhan, C., Christoforidi, I., Dindaroglu, T., Fois, M., Manolaki, P., Sandor, A., Sieber, I., Valentini, S., Tzirkalli, E., Vogiatzakis, I., Zemah-Shamir, Z., and Moustakas, A.: Climate change and islands’ ecosystem services: a global meta-analysis , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16829,, 2024.

On-site presentation
Niels A.G.M. van Helmond, Olga M. Zygadlowska, Robin Klomp, Wytze K. Lenstra, Mike S.M. Jetten, and Caroline P. Slomp

Increased anthropogenic activities are affecting water quality, e.g. leading to eutrophication and deoxygenation, culminating in biodiversity loss in coastal ecosystems globally. In the Southwest Delta in the Netherlands, large scale engineering to protect coastal areas against storm surges has turned several tidal inlets and estuaries into coastal lagoons and (marine) lakes. The water quality in these ecosystems has strongly deteriorated as a result of stagnation of bottom waters in combination with eutrophication. One such ecosystem, Lake Veere, showed signs of recovery after restoration of water exchange with the adjacent tidal marine Eastern Scheldt in 2004. In recent years, regular water monitoring has revealed the return of low-oxygen conditions, however, along with other signs of worsening water quality such as fish kills and jellyfish blooms. Here, we assess the role of the sediments in the (re)occurrence of low-oxygen conditions in Lake Veere. During two sampling campaigns in 2022, water column and sediment samples were collected. Geochemical analysis, including direct in-situ flux measurements with a benthic lander, revealed an increasing sedimentary oxygen demand (SOD) from the western (sea-side) part of the lake to the east, from ~10 to >100 mmol O2 m-2 d-1. This gradient in SOD opposes the observed trend in water column deoxygenation, with low-oxygen conditions predominantly prevailing in the central and western part of the lake and not in the east. This indicates that, despite restoration efforts, large parts of the lake are still highly sensitive to deoxygenation. Sediment analyses show the near-absence of iron-oxides, hence little capacity to buffer toxic hydrogen sulfide, which indeed accumulated in pore waters, reaching concentrations of up to 10 mmol L-1. In the central part of the lake, hydrogen sulfide even accumulated in the bottom waters, pointing towards its potential involvement in the observed fish kills in the region. Our results illustrate the difficulty of improving water quality through changes in water exchange alone because of strong legacy effects of eutrophication and deoxygenation in the sediment.  

How to cite: van Helmond, N. A. G. M., Zygadlowska, O. M., Klomp, R., Lenstra, W. K., Jetten, M. S. M., and Slomp, C. P.: Variable effects of ecosystem restoration in a eutrophic coastal lagoon: reoxygenation by increasing water exchange, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4081,, 2024.

On-site presentation
Guglielmo Federico Antonio Brunetti, Manuela Carini, Maria Antonietta Scarcella, Francisco Xavier Pilier, and Mario Maiolo

Coastal areas globally are invaluable assets and strategic resources from both environmental and social perspectives, as well as for the sustainable development of the marine economy, often referred to as “Blue Growth”. This understanding highlights the crucial need to protect coastal areas from climate change phenomena such as sea-level rise, flooding, and erosion. Previous research has shown the high vulnerability of the Mediterranean Sea's coasts to these phenomena, with ecosystems and biodiversity increasingly under threat. Despite past efforts to address these issues, many aspects still require further investigation, and solutions necessitate a holistic approach and a step-by-step strategy. Our research contributes to this context by providing valuable insights from Calabaia Beach (Calabria, Italy), where specific step-by-step strategies were implemented to mitigate erosion processes and restore the coastal and marine environment. The research site, located within the Marine Experimental Station of Capo Tirone (Belvedere Marittimo, Calabria, Italy), is of significant relevance as it has experienced various sea-defense interventions over the years, ranging from hard defenses to soft defenses, to the adoption of nature-based solutions. This study highlights that investigating the efficacy of these interventions over time can offer essential insights into the potential of each to sustainably curb erosion processes. From this standpoint, practitioners can establish a solid foundation to predict how future interventions for tackling erosion could effectively impact the entire coastal ecosystem of the area. Moreover, our research suggests that a step-by-step approach could be implemented also for aspects related to local hydrodynamics, pollutant dispersion, seawater intrusion, and marine biology. The case study of Calabaia Beach clearly illustrates that a time-dependent strategy could be successfully applied when there is a need to balance coastal environmental protection with social interests and the development of “Blue Growth”. This approach could be further explored in other case studies, keeping in mind that the specific characteristics of the area represent a determining factor.

Acknowledgements. This research was supported by ”NAUTILOS” project (GA 101000825) and by the Next Generation EU - Italian NRRP, Mission 4, Component 2, Investment 1.5, call for the creation and strengthening of ’Innovation Ecosystems’, building ’Territorial R&D Leaders’ (D. D. 2021/3277) - project Tech4You, n. ECS0000009. This work reflects only the authors’ views and opinions, neither the Ministry for University and Research nor the European Commission can be considered responsible for them.

How to cite: Brunetti, G. F. A., Carini, M., Scarcella, M. A., Xavier Pilier, F., and Maiolo, M.: Step-by-Step Strategies to Tackle Coastal Erosion: Insights from Calabaia Beach (Calabria, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15795,, 2024.

Posters on site: Wed, 17 Apr, 10:45–12:30 | Hall X5

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 12:30
Chairpersons: Sara E. Anthony, Eva Ehrnsten, Fereidoun Rezanezhad
Melanie Biausque, Darragh O'Suilleabháin, Lee Wah-Pay, and Emma Verling

Nature-based solutions (NbS) at the coast are, by definition, methods developed to work with nature to sustainably protect, restore and/or manage the shore. They can be classified into 4 main categories such as fully natural solutions, managed natural solutions, hybrid solutions and ‘green’ engineering solutions. As part of the EU Mission: ‘Restore our ocean and waters by 2030’, the Horizon Europe-funded Atlantic-Arctic Agora (A-AAgora) project identifies innovative solutions, including NbS, to co-develop coastal restoration actions in association with nature and people, throughout 3 demonstration areas. In this context, Demo Ireland locally adapted the ‘living lab’ approach via community-led actions undertaken at Harper’s Island, Co. Cork. Managed and hybrid NbS, for instance livestock grazing, control of invasive species (Spartina), development of pollinator areas, etc…, were successfully tested, supporting coastal wetland restoration and significantly enhancing local biodiversity. NbS deployed by communities at Harper’s Island, with the support of Cork County Council, were then described and reported, allowing their replication to the whole island of Ireland, and overseas. Moreover, additional sites facing coastal erosion and tidal flooding issues were selected and monitored along the Co. Cork coastline. Preliminary results allowed us to identify the main coastal challenges for each site in association with local geomorphological patterns and hydrodynamics, in a context of climate change. The next step for the A-AAgora project in Ireland is to identify suitable NbS as sustainable solutions and long-term management actions, to tackle coastal challenges in those areas. Moreover, this ongoing work is carried-out with the collaboration of multiple stakeholders, such as scientists, decision makers and communities. While these methods have been developed at local scales in the south of Ireland, they can be reproduced and upscaled in other areas, further raising global awareness about coastal adaptation and coastal sustainable solutions/managements.

How to cite: Biausque, M., O'Suilleabháin, D., Wah-Pay, L., and Verling, E.: The use of nature-based solutions (NbS) for coastal restoration actions and biodiversity protection: the A-AAgora project for Ireland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-516,, 2024.

Stefan Forster, Hanna Schade, and Werna Werna

Coastal sediments are frequently permeable due to their relatively large grains size. Knowledge on exchange processes across the sediment-water interface and metabolism in these sediments is limited however. We characterize permeable sediments at about 5 m water depth in a coastal stretch of ~3.5 km² at the southern Baltic coast off Germany. Permeability ranged from 1.4 .10-12 m² to 11.3 .10-11 m² (organic content: 0.1% - 0.2% dry mass). We determined total oxygen uptake, TOU, of 10 – 28 mmol O2 m² d-1 from in situ measurements in the dark. Benthic net primary production determined in situ varied between 1 - 14 mmol O2 m² d-1.
We observed an increase in volumetric oxygen uptake rates in flow-through experiments when highly reactive glucose was supplied as substrate, pointing to the pivotal role of reactive organic substrate availability. However, we could detect only marginally enhanced TOU (uptake doubled at one out of three locations) when applying stirring rates inducing pore water flow in benthic chambers under natural conditions. We conclude that stimulating effects of permeability associated with pore water flow are not detectable in benthic exchange rates below a threshold of 7 .10-11 m² under field conditions. This threshold is higher than previously reported.
Ex situ experiments demonstrated that the distribution of oxygen in the sediment was affected by photosynthetic activity of microphytobenthos and by pore water flow. Benthic primary production determined by the dark-light shift method exceeded the summed fluxes of oxygen into the water and into the sediment driven by concertation gradients, and increased with light intensity as well as with organic substrate availability. These findings indicate that calculated net ecosystem metabolism can shift from autotrophy to heterotrophy owed to an increased consumption within the sediment during advection. We argue that under advective conditions the export flux of photosynthetically produced oxygen may differ from the flux under diffusive conditions. This may seriously impair photosynthesis rate determinations obtained from incubation experiments.

How to cite: Forster, S., Schade, H., and Werna, W.: Surface sediment permeability and reactivity in a shallow coastal environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1790,, 2024.

Joseph Earl, Suzana Ilic, Alexandra Gormally-Sutton, and Michael R. James

Coastal communities in North West England face numerous anthropogenic challenges, including high vulnerability to the impacts of climate change, namely enhanced coastal erosion and flooding from sea level rise (Sayers et al., 2022), and marine litter. To manage heightening climate impacts, Flood and Coastal Management has transitioned from a defence to risk-based management, including a focus on building coastal system resilience through Nature-based Solutions (NbS) rather than physical defences. Building the resilience of people, including coastal communities, is critical to this transition, whereby their voices are heard and they can better prepare for these risks (EA, 2020). However, despite the strategic intent to engage and involve people, public participation in practice has been restricted by numerous challenges, perpetuating a continued lack of public involvement in decision making or resilience building.

This interdisciplinary project investigates whether such a deficit in public engagement in decision making can be overcome through a case study citizen science project called Coast Watchers at Rossall on the North West coast, which aims to collaboratively engage people in monitoring and responding to coastal challenges. The research embarked on several study phases to iteratively design, test and evolve the citizen science project collaboratively, involving various coastal monitoring activities and social science investigations. Results suggest that it is important to account for people’s local coastal values, motivations and concerns (Earl et al., 2022) when designing a collaborative approach to public engagement.

Crucially, the work explores the extent to which coastal communities can be engaged beyond citizen science monitoring and become active participants in a resilient and collaborative coastal management. The talk will present outcomes from a series of interviews with coastal practitioners and community members in the North West, exploring the challenges and opportunities for communities to be more involved in a collaborative coastal management. Findings will be discussed within a wider context, whereby they are contributing towards a Flood and Coastal Resilience Innovation Project, Our Future Coast (EA, 2022), which seeks to engage people in adaptation planning and co-designing NbS to better protect coastal communities around the North West coast from current and future challenges.



Earl, J., Gormally-Sutton, A., Ilic, S. and James, M.R. (2022). ‘Best day since the bad germs came’: Exploring changing experiences in and the value of coastal blue space during the COVID-19 pandemic, a Fylde Coast case study. Coastal Studies & Society, 1(1), pp.97-119.

Environment Agency (2020) National Flood and Coastal Erosion Risk Management Strategy for England. [14/9/23]

Environment Agency (2022) Flood and Coastal Resilience Innovation Programme. [7/2/23]

Sayers, P., Moss, C., Carr, S. and Payo Garcia, A. (2022) Responding to climate change around England's coast: the scale of the transformational challenge. Ocean & Coastal Management, 225.

How to cite: Earl, J., Ilic, S., Gormally-Sutton, A., and James, M. R.: Collaborative Citizen Science to Support Coastal Management, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3820,, 2024.

Zhe Zhou and Shouye Yang

Coastal permeable sediments cover 50-60% of the continental shelves and are important filters and bioreactors that sitting between the land and ocean. In permeable surface sediments, the dynamic porewater advection can lead to frequent redox oscillation, which significantly affects the coupled cycling of organic matter (OM) and iron. In our study, we focused on the most redox active iron fraction (extractable by 0.5 M HCl), and investigated their effects on OM degradation and retention. During the transition of redox conditions, Fe(III) oxyhydroxides were quantitatively found as the dominant electron acceptors for anaerobic OM remineralization. However, the release of reduced Fe was significantly delayed, with most Fe(II) (~96%) remaining in the solid phase either through adsorption or formation of authigenic Fe(II)-bearing minerals. Under frequent redox oscillation as typically observed in natural coastal permeable sediments, Fe(II) in the solid phase can be re-oxidized and repetitively used as electron acceptor for anaerobic OM remineralization (Iron “redox battery”). In addition, based on our field study along near- to offshore transect in the North Sea, we found that the most redox active iron trapped abundant of dissolved OM (54±20 times than DOM in porewater) that enriched in aromatic and oxygen-rich compounds. It indicates that iron may preferentially promote the retention of terrigenous and aromatic DOM in permeable sediments, thus serving as an important temporal storage for terrigenous OM in the coastal ocean. Further investigations of the dynamic Fe-OM interactions in coastal sediments are warranted to better understand carbon cycling in the coastal area. 

How to cite: Zhou, Z. and Yang, S.: Iron mediated organic matter cycling in permeable surface sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7418,, 2024.

Sergey Venevsky, Sergey Berdnikov, Victoria Gerasjuk, Vera Sorokina, Aleksey Kleshchenkov, Igor Sheverdyaev, Valerii Kulygin, and Natalia Lichtanskaia

The Don River Delta, bordering the Taganrog Bay in the Sea of Azov, is one of the major deltas of Europe, providing important ecological and economic services. The Sea of Azov is an enclosed sea, which is also the shallowest sea on the globe (the mean depth is 7 meters) with rich biological productivity.

It was indicated recently that both the Sea of Azov (Berdnikov et al, 2023) and the Don Delta (Venevsky et al, 2023), as well as the estuary area have undergone significant environmental transformations in the last four decades. The water temperature and salinity in the sea and the estuary increased to the never observed values mostly due to climate change (Berdnikov et al, 2023) and the prevailing wind directions changed to the westerlies bringing strong upward surges to the delta. Meanwhile, the Don River runoff significantly dropped started from 2007, while fluvial sediments delivery to the Don Delta were steadily diminishing already during 70 years due to the constructions of dams, human land use and runoff regulation (Venevsky  et al, 2023). Significant amount of suspended sediments from the Taganrog Bay enters the delta and salty waters intrusions to the delta are frequent during surges driven by the westerlies. Thus, the role of marine factors in the delta and estuary area of the Don increased in the last few decades in comparison with fluvial factors. Carbon sequestration in coastal areas considered to be the so-named natural solution for climate change mitigation. Thus, it is important to estimate the past, present and future carbon balance of the Don Delta and the estuary, especially accounting that the delta undergoes changes from being fluvial dominated to marine (wave and surge) dominated one.

We are currently involved in the study focusing on the quantification of carbon pools and fluxes in the Don Delta and the estuary. The study combines modelling approach with field observations and remote sensing data. Our field data included seasonal observations for 2006-2020 of total suspended solids, salinity, concentration of dissolved and suspended organic matter, and chlorophyll-a concentration in the river-delta-estuary continuum (the Lower Don River -Delta-Taganrog Bay). Remote sensing included Landsat and Sentinel images for upward surges episodes for the same period.  We use three combined models:  a hydrological model of the Don estuary area (DonDeltaHECRAS) for simulation of the river flow and water levels during surges; model of suspended matter dynamics (DonDeltaBalanceModel), which allows us to calculate the suspended matter dynamics in the Don estuary area; and model of vegetation and soil dynamics (DonDeltaEcoModel), which is aimed at estimating the carbon accumulation in vegetation and soil in the delta. We found out that with the recent frequency of surges on average 20% of organic chemicals transported with the river runoff is deposited in the delta. Thus, marine factors affect accretion of soil within the delta and change both the carbon pools and fluxes in the delta and the estuary.

How to cite: Venevsky, S., Berdnikov, S., Gerasjuk, V., Sorokina, V., Kleshchenkov, A., Sheverdyaev, I., Kulygin, V., and Lichtanskaia, N.: Dynamics of carbon pools and fluxes in the Don River Delta, Southern (European) Russia, and the estuary under the conditions of increasing marine factors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8832,, 2024.

Amabelle Go, Hendrik Schubert, and Gerald Jurasinski

Coastal peatlands, despite their ecological importance are at risk from a range of disturbances that render this habitat vulnerable, affecting their productivity and could potentially trigger ecosystem shift. Salinity is one of the factors affecting the structural and functional aspects of macrophytes in peatland environments. This study aims to assess the impacts of different salinity levels on the growth, biomass, and photosynthetic performance of peatland plants using a mesocosm approach. Four treatments of varying salinity were implemented: Saline (C+) with salinity of 20 ppt, Freshwater (C-) with salinity of 0 ppt, 22 and 55 pulses where the plants were exposed alternately to water with salinities of 20 ppt and 0 ppt every 2 and 5 days, respectively.  Two macrophyte species, Phragmites australis and Typha latifolia, were planted in mesocosm tanks. Over a 16-week period, various parameters including leaf length, leaf area, plant height, growth, biomass, and photosynthetic responses were monitored to evaluate the extent of salinity-induced stress. Results indicate that P. australis exhibited no significant difference in growth rates and biomass across treatments. Growth monitoring showed peak observed at the 8th week post-transplanting. Leaf area and leaf production also showed no significant variations. While shoot production increased initially, peaked at the 8th week, and declined thereafter. T. latifolia on the other hand, displayed growth rate variations favoring the freshwater (C-) and less frequent water change (55) treatments. The 55 pulses exhibited the highest absolute growth rate, but growth regressed after 8th week in treatments exposed to salinity changes. Leaf production in saline (C+) and higher frequency of water changes (22) showed a steep decline from 10th week onward. Saline treatment resulted in the lowest leaf production, leaf area, and biomass. This study contributes insights on the varying responses of macrophytes to salinity stress, demonstrating acclimation kinetics, and identifying salinity limits. 

How to cite: Go, A., Schubert, H., and Jurasinski, G.: Salinity influence on plant traits and photosynthesis in selected peatland macrophytes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9443,, 2024.

The MANABAS COAST project: Mainstreaming Nature-Based Solutions through coastal systems
Jurre de Vries, Lisa van Well, Per Sorensen, Frances Kannekens, Quirijn Lodder, Berry Gersonius, and Matthijs Boersema
Lloyd Reese, Ulf Gräwe, Xaver Lange, and Hans Burchard

Due to their shallow depth, coastal lagoons are often considered to be vertically well-mixed. However, past studies have shown that, depending on forcing conditions, vertical density stratification may in fact occur even in lagoons of only a few meters depth. Further, many coastal lagoons are faced with a multitude of anthropogenically caused pressures, including eutrophication as well as a likely increasing occurrence of summer heatwaves and other extreme atmospheric conditions due to climate change. While eutrophication leads to increased biological productivity and a subsequently increased oxygen demand, high water temperatures during heatwaves lead to reduced oxygen solubility, thus aggravating the risk of anoxic conditions within the water body. As vertical stratification acts to suppress vertical mixing, it may facilitate the occurrence of bottom oxygen depletion in such waters. Since coastal lagoons are of great ecological and economical interest due to their multiple ecosystem services, e.g., as spawning grounds for fish, it is of utmost importance to assess the conditions under which vertical stratification may occur. Only with such knowledge it will be possible to estimate the future development of coastal lagoon ecosystems. While many past studies have covered stratification of freshwater lakes during heatwaves, there is a significant gap of research covering coastal lagoons under the same conditions, where an additional forcing is added via the connection to the open sea. In particular, non-tidal, non-choked lagoons are currently understudied with respect to summer heatwaves. In our study, we therefore aim to assess the conditions under which stratification may occur in such lagoons during a mid-latitude summer heatwave. To this end, we have applied a non-dimensional parameter space analysis to a numerical, one-dimensional water column simulation of such a lagoon. Here, we present first results from this analysis.

How to cite: Reese, L., Gräwe, U., Lange, X., and Burchard, H.: Stratification in non-tidal shallow coastal lagoons during extreme summer heatwaves , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10491,, 2024.

Julia Jaca Estepa and Gabriel Jordà Sánchez

Climate change is already modifying the marine environment, and these alterations will presumably increase in the coming decades. Some of the most significant changes expected during this period include ocean warming, rise of sea level, and modifications to circulation and wind wave patterns. For instance, in the Mediterranean, ocean surface temperatures are projected to increase by 1-4 ºC by the end of the century, triggering a chain of impacts on marine ecosystems, such as species migration, significant mortality in some species, and an increase in harmful algal blooms.
Furthermore, sea levels are expected to rise, reaching values ranging from 30 cm to over 1 m by the end of the century. The consequences include the increased permanent flooding of low-lying areas, the salinization of coastal water reservoirs, and damage caused by marine storms.

In this context, despite ongoing efforts to reduce greenhouse gas emissions, it is crucial to develop realistic and effective plans for adapting to climate change. Nature-based solutions (NBS) present a particularly interesting approach to addressing climate change impacts. One NBS option suitable for reducing the impacts of climate change in coastal areas is to increase seagrass meadows through restoration interventions. The interaction of seagrasses with water flow leads to a reduction in flow energy, thereby limiting the impact of waves reaching the coast.
However, ocean warming poses a threat to seagrass meadows, as some species are particularly vulnerable to marine heatwaves. Therefore, the primary goal of the SEAFRONT project is to quantify the potential benefits of seagrass meadows in protecting the coast from future marine storms under different scenarios of global warming and seagrass evolution. SEAFRONT focuses on Spanish coastal areas, which exhibit a variety of hydrodynamical situations and seagrass coverages.
Specifically, SEAFRONT aims to 1) assess the impacts of marine storms over the last decades, evaluating the role of seagrasses; and 2) generate future scenarios of physical and economic impacts.

In this presentation, we share the results of numerical simulations focused on measuring the total water level at the shore under various scenarios. These simulations account for sea level changes, wave patterns, coastal shapes, and seagrass coverage. Additionally, we discuss the economic impacts of marine storms based on information from insurance companies.
Our initial analyses suggest that restoring seagrass meadows is a highly effective way to adapt to marine storms, countering the effects of rising sea levels. However, in areas where seagrasses already exist, losing them could lead to severe consequences, increasing the impact of marine storms.

How to cite: Jaca Estepa, J. and Jordà Sánchez, G.: Seagrass meadows provide essential coastal protection against future marine storms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11191,, 2024.

Aarno T. Kotilainen, Mia M. Kotilainen, Sami Jokinen, Meri Sahiluoto, Joonas J. Virtasalo, and Anu M. Kaskela

River estuaries are diverse coastal ecosystems that have significant ecological, social, cultural and economic value. Estuaries worldwide are stressed by increasingly intensive human activities, also in the Baltic Sea, a European inland sea. Human pressures include e.g., dredging, port constructions, river water acidification and pollutants. In the latest assessment of threatened habitat types in Finland, coastal estuaries were assessed as an Endangered (EN) habitat complex due to historical abiotic and biotic quality changes.

As estuaries are often very shallow environments with turbid water column, it is not easy to acquire detailed seabed information from those areas. In the ongoing SeaMoreEco project we use remote sensing methods such as shipborne acoustic surveys, floating drones, flying drones and satellites, as well as seabed sampling and underwater video observations to map and monitor shallow water areas of the Gulf of Bothnia (GoB), northern Baltic Sea. We provide information e.g., on seabed geology and underwater vegetation. Here, we focus on seabed sediment data produced in the SeaMoreEco and in some other projects.

Anthropogenic radionuclides and heavy metal pollution are typical pressures widely affecting river estuaries and other marine ecosystems. For example, the fallout from the April 1986 Chernobyl nuclear power plant accident has rendered the Baltic Sea as the most polluted marine body in the world with respect to 137Caesium (137Cs). In the present study we determined the levels of 137Cs activity and heavy metal content in the bottom sediments, and their spatial and vertical distribution in the subsurface sediments of the GoB.

Activity contents of 137Cs and heavy metal contents in seabed surface sediments of the GoB have generally declined over the last decades. In some estuaries however, 137Cs values in subsurface sediments remain at elevated levels relative to values measured from other areas of the Baltic Sea. In some areas, also the contents of heavy metals (e.g., cadmium, lead, zinc) in the subsurface sediments are quite high. This is typical for areas close to e.g., the metal industry and the areas affected by the loading from acid sulfate soils.

Data on harmful substances (e.g., radionuclides) in seabed sediments is important for coastal management and marine spatial planning while assessing risks associated with dredging and other operations. Dredging in areas where bottom sediments contain a lot of harmful substances can cause the re-mobilization and transport of these contaminants. Increasing anthropogenic pressures in coastal and marine areas will likely increase risk associated with polluted bottom sediments. Climate change might also shift many of the parameters (precipitation,  river discharge) that affect sediment distribution and pollution in the coastal and marine areas, also in the GoB.

This study is part of the Interreg Aurora funded SeaMoreEco project, the EMODnet Geology project funded by The European Climate, Environment, and Infrastructure Executive Agency (CINEA) through contract EASME/EMFF/2020/3.1.11/Lot 2/SI2.853812 - EMODnet Geology, the EMODnet Ingestion 3 project funded by the CINEA through contract CINEA/EMFAF/2021/3.4.10/02/SI2.868290, and the MAAMERI project funded by the Ministry of Environment, Finland. The study utilized research infrastructure facilities provided by FINMARI (Finnish Marine Research Infrastructure network).

How to cite: Kotilainen, A. T., Kotilainen, M. M., Jokinen, S., Sahiluoto, M., Virtasalo, J. J., and Kaskela, A. M.: Estuaries under pressure – surveying the extreme shallow water environments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11676,, 2024.

Lev Naumov, H.E. Markus Meier, and Thomas Neumann

The Baltic Sea is a semi-enclosed sea located in the Northern Europe. Due to the limited exchange with the Global Ocean, which leads to the long residence time (approx. 30 years), and permanent halocline, the Baltic Sea is naturally prone to hypoxic conditions, especially in the deep basins. However, the hypoxic area in the deep Baltic Sea has been rapidly increasing since the second half of the 20th century following the elevated nutrient input caused by human activity. To mitigate the eutrophication of the Baltic Sea, countries surrounding it started to reduce their nutrient loads following the Baltic Sea Action Plan. Despite the substantial nutrient input reduction, no significant decrease in the hypoxic area has yet been observed. In addition, climate change might promote deoxygenation of the Baltic Sea, further hampering nutrient load reduction efforts. The non-linear response to changes in nutrient input raises the question of when to expect the robust reduction of the hypoxic area, whether it is possible for the Baltic Sea to return to its natural state with a limited hypoxic area, and how the composition of the oxygen budget will change following the reduction of hypoxia.

To answer those questions, we conducted two sensitivity simulations utilizing a 3-dimensional coupled physical-biogeochemical model. The simulations followed the two nutrient reduction pathways – Baltic Sea Action Plan Maximum Allowable Input (BSAP) and the more radical half of the BSAP MAI (0.5 BSAP). Both simulations spanned 71 years and were compared to the reference scenario (Ref.) employing observed nutrient loads from 1948 to 2018. The lowering of the hypoxic area was observed in both scenarios. Most rapid re-oxidation was observed in the remote northern and western Gotland Basins, especially in the 0.5 BSAP scenario. The redistribution of the biggest oxygen consumption from the water column to the sediments followed it. Changes in nutrient loads explain more than 60% of the oxygen sources and sinks variability, making it the dominant driver of changes in the oxygen budget of the Baltic Sea, at least in the near future. The Baltic Sea could return to its initial state (1948) within the simulation period, but only following the radical 0.5 BSAP scenario.

How to cite: Naumov, L., Meier, H. E. M., and Neumann, T.: Oxygen dynamics in the Baltic Sea under reduced nutrient input, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12994,, 2024.

Isabella Scroccaro, Celia Laurent, Leslie Aveytua, Cosimo Solidoro, and Donata Canu

Coastal and transitional areas worldwide are affected by a range of human pressures and are subjected to high natural variability. In the Marano and Grado lagoon, located in the densely anthropized north-eastern coastal area of Italy, the conservation of biodiversity and the presence of important socio-economic activities require planning and management tools and measures. Coupled physical and biogeochemical models are useful tools to support trophic studies in complex systems such as the Marano and Grado lagoon by integrating field information with relevant hydrodynamic and biogeochemical processes shaping the system. The coupled SHYFEM–BFM model was applied to the Marano-Grado lagoon, adding new features to account for the contribution of macrophytes (such as seagrasses). Results were validated against available in situ observations, and trophic properties were investigated using trophic state indices that allow to reproduce spatial and temporal variability under different scenarios.

How to cite: Scroccaro, I., Laurent, C., Aveytua, L., Solidoro, C., and Canu, D.: Assessing the spatial and temporal trophic properties of the Marano and Grado Lagoon, Italy with the coupled physical-biogeochemical model SHYFEM-BFM , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15787,, 2024.

Bernd Lennartz, Rosa Cambinda, Haojie Liu, and Fereidoun Rezanezhad

Carbon loss from peatlands involves both gaseous emissions and a significant contribution from the water-bound fraction, specifically dissolved organic carbon (DOC), during mineralization and degradation processes. Our hypothesis proposes that DOC production is dependent on pore size, with elevated concentrations occurring in finer pores. To test this hypothesis, we extracted pore water at well-defined pressure heads (-60 and -600 hPa), representing macro- and mid-size pore domains, in degraded peat samples. Topsoil and subsoil samples exhibited soil organic matter contents of 34wt% and 57wt%, respectively. Remarkably, the more degraded topsoil consistently displayed significantly higher average DOC concentrations than the subsoil, with 1.5 times greater levels at -60 hPa and 2.4 times higher at -600 hPa. This trend suggests that more degraded peat soils are prone to releasing higher amounts of DOC. Furthermore, in topsoil samples, DOC concentrations were consistently higher at the -600 hPa pressure head compared to -60 hPa. To enhance our understanding, we computed hydraulic conductivities at -60 and -600 hPa using Van Genuchten parameter values, subsequently estimating the DOC load under unit gradient conditions. This calculation is particularly relevant for real-field situations, especially in partially saturated (degraded) peat soils. The hydraulic conductivity at -600 hPa was nearly a hundred times lower than at -60 hPa, leading to the conclusion that macro-pores serve as the primary pathways for DOC release in peat soils, irrespective of higher DOC concentrations in the fine pore domain.

How to cite: Lennartz, B., Cambinda, R., Liu, H., and Rezanezhad, F.: Pore-Size-Class Dependent Carbon Turnover in Peat Soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15930,, 2024.

Erwin Don Racasa, Haojie Liu, Miriam Toro, and Manon Janssen

Coastal peatlands are unique ecosystems situated at the interface of land and sea. Past human activities, specifically drainage, have turned these carbon sink coastal regions into carbon sources. To mitigate climate change, recent management strategies focus on rewetting drained coastal peatlands. In this study, we aimed at characterizing surface and groundwaters in two coastal fens and examine the impacts of seawater input events caused by a storm surge (freshwater-rewetted) and rewetting with seawater (seawater-rewetted). Prior to the events, our findings reveal variable marine influence on surface and groundwater in the past which depends on distance from the coast, peat thickness, and possibly, drainage networks. After the storm surge, increases in specific conductivity (SC), chloride, and sulfate concentrations in surface waters persisted for up to a year. Increases in surface water dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations were also observed. In peat groundwater, a sustained increase in DOC concentrations that reached 526 mg DOC L-1 was observed at a shallower depth (max: -0.59 masl) while a delayed increase was observed at a deeper depth (max: -1.41 masl). High dissolved carbon concentrations were still observed in peat groundwater until the end of the observation period, three years after the storm surge. For the seawater-rewetted fen, significant changes in surface water properties were observed, which included SC, chloride, pH, DOC, DIC. The initial DOC concentrations in peat groundwater decreased, but later, showed the same high concentrations similar to the storm surge flooded fen. No apparent impacts to deeper sandy aquifers from both sites were observed. Overall, storm surge flooding impact on surface water properties lasted for a limited time while rewetting with seawater significantly and drastically changed the surface waters as the peatland was transformed into a lagoon-like environment. Peat groundwater properties in both sites did not change significantly, however, depth-dependent variable increases in DOC concentrations could be expected. The increases in DOC concentrations in peat groundwater were accompanied by increased SC and decreased pH conditions. Lastly, the ongoing salinization of seawater-rewetted fens may lead to brackish-rewetted environments with higher concentrations of seawater salts and potentially create new biogeochemical reactive mixing zones of ground- and seawater.

How to cite: Racasa, E. D., Liu, H., Toro, M., and Janssen, M.: Groundwater quality in two coastal fens and the influence of storm surge flooding and rewetting with seawater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18394,, 2024.

Angelina Klett, Iris Liskow, and Maren Voss

Biological nitrogen (N) fixation is the microbial transformation of atmospheric N2 to ammonia, which is carried out by various groups of microorganisms and in all environments. The organisms, called diazotrophs, do not rely on bioavailable combined N such as nitrate or ammonium, which are often limiting ecosystem productivity. On the other hand, their activity provides nutrients to the otherwise N-limited ocean. In the central Baltic Sea high nitrogen fixation occurs each summer in surface waters introducing up to 792 000 t N per year, but was also identified in the deep and anoxic waters. In coastal waters the heterotrophic and autotrophic N2 fixation is not well studied and even less is known about the annual cycle and its regulation by the environment. Since coastal environments are considered to act as a filter for nutrients and organic matter, knowledge on an additional N source through N2 fixation is of great importance.

Here, we present N2 fixation rates for bulk water and sediment slurries (upper 5 cm), incubated for 24 hours in the dark and during a daily light cycle. We selected three stations near a peatland with outcropping peat layers and sandy sediments. Monthly sampling over the course of one year was done together with in-situ measurements of temperature, salinity, pH, nutrient concentrations and dissolved organic substances. Incubations were spiked with 15N2 gas and incubated in the lab. The fixation rates ranged from our detection limit up to 285 nmol N L-1 d-1 in water and 2 nmol N gdw-1 d-1 in sediments with a mean fixation rate of 11.2 nmol N L-1 d-1 and 0.1 nmol N gdw-1 d-1 for water and sediment, respectively. We could not find significant difference between stations and overall, the rates were much lower than in the surface waters of the central Baltic Sea. Though the rates in the water observed in June 2022 agree well with the rates of a cyanobacterial bloom in late summer (4.3 – 7.8 µmol N m-3 h-1). The rates for the water as for the sediment showed significant positive correlation (Spearman, sig. level 0.05) with variables affected by the seasonal change as temperature, daylength, pH and oxygen saturation. during winter and spring, the rates in the water were low to non-detectable and highest in summer. Also, in the sediment the lowest rates were found during winter and highest rates in spring. In general, the light cycle treatment showed higher rates than the dark incubation, with the exception of spring where the dark incubated sediments had higher rates than the ones in a daily light cycle. The outcropping peat layer seemed to induce some variability in N2 fixation rates, reflecting the heterogeneity of substrate which was sometimes covered with sand layers of different thickness.

Even though the rates in this study are comparably low for both water and sediment, a seasonal pattern became visible. Sediments and shallow waters clearly deserve more attention to better understand the process and the potential role as food and nitrogen source.

How to cite: Klett, A., Liskow, I., and Voss, M.: Nitrogen fixation in the shallow waters off a coastal wetland with outcropping peat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18697,, 2024.

Christian Sommer, Mathias Seuret, Nora Gourmelon, Vincent Christlein, and Matthias Braun

Following the current expansion of offshore constructions for the production of renewable energy as well as shipping traffic, assessments of impacts on marine ecosystems are becoming increasingly important. Thus, accurate knowledge of the spatial and temporal distribution of animal species is mandatory regarding the preservation of biodiversity and management of offshore wind farms and further economic activities. High-resolution optical imagery of airborne remote sensing sensors enables the observation of marine birds and mammals within large ocean areas. However, the identification of features at the ocean surface as well as the separation of animals and further objects, such as wave structures, ships or buoys, requires time-consuming visual inspection of the acquired image sequences by trained personnel. Here, we apply an AI-based approach to automatically detect and classify various features above the sea surface based on aerial imagery of the German North Sea and Baltic Sea. A large number of optical images at a spatial resolution of 2 cm have been acquired by the German Federal Agency for Nature Conservation (BfN) during repeated monitoring flights since 2018. These images are preprocessed and geolocated by assigning respective auxillary informations to create an extensive database on marine animal observations. The AI method which we are developing has to be responsible both for detecting birds in images, and for tracking instances of a same element present on multiple frames in order to avoid counting an individual multiple times. Some of the main challenges which will have to be dealt with are the following. First, luminosity conditions cannot be controled and might be suboptimal in a large fraction of the images, rendering animals completely white or black, or difficult to distinguish from the background. Second, smaller animals might consist only of little pixel blobs, and thus be difficult to distinguish. Third, flying birds might have shadows, which, while bird-shaped, must not be classified as birds. Fourth, in bird flocks overlapping tricks the AI into detecting one bird instead of several ones, which renders tracking significantly more challenging. We aim at tackling the third and fourth issues by incorporating cinematic estimation of the plane‘s and animal‘s movements, and estimating the direction of the sun in each frame, into the tracking system. In the future, our system will be used by the German Federal Agency for Nature Conservation (BfN) to monitor bird and mammal populations, and evaluate the effectiveness of preservation measures. 

How to cite: Sommer, C., Seuret, M., Gourmelon, N., Christlein, V., and Braun, M.: AI classification of marine birds and mammals based on aerial imagery of the German North and Baltic Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19604,, 2024.

Posters virtual: Wed, 17 Apr, 14:00–15:45 | vHall X5

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 18:00
Miaorun Wang, Haojie Liu, Fereidoun Rezanezhad, Dominik Zak, and Bernd Lennartz

Coastal peatlands have been frequently blocked from the sea and artificially drained for agriculture. With an increasing awareness of ecosystem functions, several of these coastal peatlands have been rewetted through dike removal, allowing seawater flooding. In this study, we investigated a recently rewetted peatland on the Baltic Sea coast to characterize the prevailing soils/sediments with respect to organic matter accumulation and the potential release of nutrients upon seawater flooding. Eighty disturbed soil samples were collected from two depths at different elevations (–0.90 to 0.97 m compared to sea level) and analyzed for soil organic matter (SOM) content and carbon:nitrogen (C:N) ratio. Additionally, nine undisturbed soil cores were collected from three distinct elevation groups and used in leaching experiments with alternating freshwater and Baltic Sea water. The results demonstrated a moderate to strong spatial dependence of surface elevation, SOM content, and C:N ratio. SOM content and C:N ratio were strongly negatively correlated with elevation, indicating that organic matter mineralization was restricted in low-lying areas. The results also showed that the soils at low elevations release more dissolved organic carbon (DOC) and ammonium (NH4+) than soils at high elevations. For soils at low elevations, higher DOC concentrations were observed when flushing with freshwater, whereas higher NH4+ concentrations were found when flushing with brackish water. Recorded NH4+ concentrations in organic-rich peat reached 14.82 ± 9.25 mg L–1, exceeding Baltic seawater (e.g., 0.03 mg L–1) by two orders of magnitude. A potential sea level rise may increase the export of NH4+ from low-lying and rewetted peat soils to the sea, impacting adjacent marine ecosystems. Overall, in coastal peatlands, geochemical processes (e.g., C and N cycling and release) are closely linked to microtopography and related patterns of organic matter content of the soil and sediments.

(The original article has been published in Geoderma, Volume 438, 116637; DOI: 10.1016/j.geoderma.2023.116637)

How to cite: Wang, M., Liu, H., Rezanezhad, F., Zak, D., and Lennartz, B.: The influence of microtopography on soil carbon accumulation and nutrient release from a rewetted coastal peatland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18426,, 2024.