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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13975

Large-scale eelgrass transplantation: A measure for carbon and nutrient sequestration in estuaries

Troels Lange*, Nele S. Oncken, Niels Svane, Rune Steinfurth, Erik Kristensen, Mogens R. Flindt

*Corresponding author:

ABSTRACT: The accelerated global losses of seagrass meadows makes restoration increasingly important. This restoration study was conducted in a shallow Danish estuary and describes one of the rare examples of successful large-scale eelgrass restoration, outside North America. A simplified three-step site-selection approach was successfully applied to locate an optimal site for large-scale transplantation. It consisted of (1) qualitative assessments of vegetation using aerial photos, (2) inspection of potential sites with assessments of stressor presence and potential growth conditions and (3) transplantation tests for a final assessment of site-suitability and methodology. The large-scale transplantation was initiated at the test-site with the highest shoots production. After transplantation, shoot densities developed rapidly, achieving a 70-fold increase in density after about 2 years. A rapid edge expansion (0.32 m y-1) of the transplanted area was detected using drone-based monitoring. Both the final shoot density and edge expansion were comparable to those of natural eelgrass patches in the estuary. Eelgrass transplanted areas accumulated more fine sediment particles and organic C, N and P than adjacent unvegetated sediment. Burial of organic C, N and P in eelgrass transplanted sediments was 33 ± 7.5, 6.6 ± 0.9 and 3.0 ± 0.5 g m-2 y-1, respectively. In addition, inorganic C and N was assimilated by eelgrass transplants at rates of 290 ± 22 g C m-2 y-1 and 12 ± 1.0 g N m-2 y-1. The results highlight that important ecosystem services are restored already two years after successful eelgrass restoration.