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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 22
Biogeosciences, 13, 6139-6153, 2016
https://doi.org/10.5194/bg-13-6139-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 6139-6153, 2016
https://doi.org/10.5194/bg-13-6139-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 14 Nov 2016

Research article | 14 Nov 2016

Blue carbon stocks in Baltic Sea eelgrass (Zostera marina) meadows

Maria Emilia Röhr1,2, Christoffer Boström1, Paula Canal-Vergés3, and Marianne Holmer2 Maria Emilia Röhr et al.
  • 1Åbo Akademi University, Faculty of Science and Engineering, Environmental and Marine Biology, Artillerigatan 6, 20520 Åbo, Finland
  • 2University of Southern Denmark, Department of Biology, Campusvej 55, 5230 Odense M, Denmark
  • 3Danish Shellfish Centre, DTU Aqua, Technical University of Denmark, Øroddevej 80, 7900 Nykøbing Mors, Denmark

Abstract. Although seagrasses cover only a minor fraction of the ocean seafloor, their carbon sink capacity accounts for nearly one-fifth of the total oceanic carbon burial and thus play a critical structural and functional role in many coastal ecosystems. We sampled 10 eelgrass (Zostera marina) meadows in Finland and 10 in Denmark to explore seagrass carbon stocks (Corg stock) and carbon accumulation rates (Corg accumulation) in the Baltic Sea area. The study sites represent a gradient from sheltered to exposed locations in both regions to reflect expected minimum and maximum stocks and accumulation. The Corg stock integrated over the top 25cm of the sediment averaged 627gCm−2 in Finland, while in Denmark the average Corg stock was over 6 times higher (4324gCm−2). A conservative estimate of the total organic carbon pool in the regions ranged between 6.98 and 44.9tCha−1. Our results suggest that the Finnish eelgrass meadows are minor carbon sinks compared to the Danish meadows, and that majority of the Corg produced in the Finnish meadows is exported. Our analysis further showed that >40% of the variation in the Corg stocks was explained by sediment characteristics, i.e. dry density, porosity and silt content. In addition, our analysis show that the root:shoot ratio of Z. marina explained >12% and the contribution of Z. marina detritus to the sediment surface Corg pool explained >10% of the variation in the Corg stocks. The mean monetary value for the present carbon storage and carbon sink capacity of eelgrass meadows in Finland and Denmark, were 281 and 1809EURha−1, respectively. For a more comprehensive picture of seagrass carbon storage capacity, we conclude that future blue carbon studies should, in a more integrative way, investigate the interactions between sediment biogeochemistry, seascape structure, plant species architecture and the hydrodynamic regime.

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Our results show that Finnish eelgrass meadows are minor carbon sinks compared to the Danish meadows, and that majority of the Corg produced in the Finnish meadows is exported. Similarly, the estimates for Corg accumulation in Finnish meadows were over 1 magnitude lower compared to Denmark. Our results further showed that > 40 % of the variation in the Corg stocks was explained by sediment characteristics. To clarify the role of seagrasses in global carbon budget, more studies are in urgent need.
Our results show that Finnish eelgrass meadows are minor carbon sinks compared to the Danish...
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