- 1Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Huddinge, Sweden (martin.dahl@sh.se)
- 2Department of Biological and Environmental Sciences, University of Gothenburg, Kristineberg, Fiskebäckskil, Sweden
- 3Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
- 4Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas (CEAB-CSIC), Blanes, Spain
- 5Centre for Marine Ecosystems Research, School of Natural Sciences, Edith Cowan University, Joondalup WA, Australia
- 6Center for Physical Sciences and Technology, Vilnius, Lithuania
- 7Pyrolyscience, Santiago de Compostela, Spain
- 8Department of Geological Sciences, Stockholm University, Stockholm, Sweden
- 9Regional Climate Group, Department of Earth Sciences, University of Gothenburg, Sweden
- 10International Atomic Energy Agency, Principality of Monaco, Monaco
- 11Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
Eutrophication and climate change are among the most severe and long-standing environmental problems threatening a large variety of coastal habitats and species in the Baltic Sea and elsewhere. Urgent and adequate management actions are needed to mitigate the combined effects of climate change and anthropogenic activities. The overall purpose of this study is to assess the relative influence of past and future climate and land-use change on organic carbon (OC) and total nitrogen (TN) accumulation in Baltic Sea coastal sediments. Preliminary results from vegetated sediments (two monospecific Zostera marina meadows and one mixed habitat with other rooted vegetation) show higher mean OC accumulation rates (17.5 ± 3.7 g m-2 yr-1)in comparison to adjacent unvegetated sediments (14.2 ± 4.0 g m-2 yr-1) but similar mean TN accumulation (2.1 ± 0.4 and 2.0 ± 0.1 g m-2 yr-1, respectively) during the last century. Based on age-depth models and 14C-dated seagrass remains in the sediment, the colonization of the monospecific Z. marina meadows were dated to approximately 100 and 200 years ago (corresponding to 10 and 15 cm sediment depths). The establishment of the seagrass meadows seems to have led to large changes in sediment biogeochemical properties, including increases in %OC, TN and silt-clay content as well as higher proportion of refractory organic matter (lignin and phenol products) and a decrease in sediment density. A similar change pattern in sediment properties (except for no apparent changes in silt-clay and phenol content) was observed in the mixed Z. marina meadow, while this occurred already 2800 (±200) years ago (seen at about 48 cm sediment depth), which was likely due to the site’s location closer to land and more rapid geomorphological changes following land uplift compared to the monospecific Z. marina meadows. There were increased δ15N values during the last 50 to 100 years, which could be a result of increasing nutrient loads from agricultural activities and land-use change. Further analysis using regional land-use and climate models are being applied to decipher the effect of land-use changes, coastal exploitation, and climate change on OC and TN storage in coastal Baltic Sea vegetation and underlying sediments over centennial to millennial scales. This information can help guide coastal management to mitigate further human-induced impacts on coastal ecosystems.
How to cite: Dahl, M., Andrén, E., Asplund, M. E., Björk, M., Mateo, M. A., Serrano, O., Andrén, T., Braun, S., Ežerinskis, Z., Forsberg, S. C., Garbaras, A., Kaal, J., Kylander, M. E., Linderholm, H. W., Madhavu, V. F., Masqué, P., Šapolaitė, J., Svensson, J. R., Vinogradova, O., and Gullström, M.: Influence of past and future climate and land-use change on carbon and nitrogen accumulation in Baltic Sea seagrass meadows, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15220, https://doi.org/10.5194/egusphere-egu25-15220, 2025.
