ALBERT

Description: Although seagrasses cover only a minor fraction of the ocean seafloor, their carbon sink capacity account for nearly one-fifth of the 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 the seagrass carbon stocks (Corg stock) and the carbon accumulation (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 25 cm of the sediment averaged 627g C m−2 in Finland, while in Denmark the average Corg stock was over six times higher (4324 g C m−2). A conservative estimate of the total carbon pool in the regions ranged between 8.6–46.2 t ha−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. Similarly, the estimates for Corg accumulation in eelgrass meadows in Finland (〈 0.002–0.033 t C y−1) were over two orders of magnitude lower compared to Denmark (0.376–3.636 Corg t y−1). Our analysis further showed that 〉 40 % of the variation in the Corg stocks was explained by sediment characteristics (density, porosity and silt content). In addition, the DistLm analysis showed, that root: shoot- ratio of Z. marina explained 〉 12 % and contribution of Z. marina detritus to the sediment surface Corg pool 〉 10 % of the variation in the Corg stocks, whereas annual eelgrass production explained additional 2.3 %. The mean monetary value for the present carbon storage and sequestration capacity of eelgrass meadows at Finland and Denmark, were 346 and 1862 € ha−1, respectively. We conclude that in order to produce reliable estimates on the magnitude of eelgrass Corg stocks, Corg accumulation and the monetary value of these services, more Blue Carbon studies investigating the role of sediment biogeochemistry, seascape structure, plant species architecture and hydrodynamic regime for seagrass carbon storage capacity are in urgent need.

Description: 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 25 cm of the sediment averaged 627 g C m−2 in Finland, while in Denmark the average Corg stock was over 6 times higher (4324 g C m−2). A conservative estimate of the total organic carbon pool in the regions ranged between 6.98 and 44.9 t C ha−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 1809 EUR ha−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.

Description: As habitat mapping is crucially important for developing effective management and restoration plans, the aim of this work was to produce a census of available map resources at the European scale focusing on: a) key marine habitats; b) degraded habitats; c) human activities and pressures acting on degraded habitats, and d) the restoration potential of degraded habitats. Almost half of the 580 map records were derived from grey literature and web resources but contained no georeferenced files for download, thus limiting further use of the data. Biogeographical heterogeneity was observed and varied between the type and quality of information provided. This variability was mainly related to differences in research efforts and stakeholder focus. Habitat degradation was assessed in only 28% of the map records and was mostly carried out in a qualitative manner. Less than half of the map records included assessments on the recovery/restoration potential of the degraded habitats, with passive restoration by removal of human activities being the most commonly recommended measure. The current work has identified several gaps and challenges both in the thematic and geographic coverage of the available map resources, as well as in the approaches implemented for the harmonized assessment of habitat degradation. These should guide future mapping initiatives in order to more comprehensively support and advise the marine habitat restoration agenda for better meeting the objectives set in relevant policy documents and legislative acts in Europe.