[A-CG50] [JJ] Coastal Ecosystems -- 2. Coral reefs, seagrass and macroalgal beds, and mangroves

[ACG50-02] Carbon sequestration and storage in seagrass meadows

★Invited papers

*Kenta WATANABE¹, Koji SEIKE², Tatsuki TOKORO¹, Shigeru MONTANI³, Tomohiro KUWAE¹ (1.Port and Airport Research Institute, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, 3.Hokkaido University)

Keywords:seagrass meadows, carbon storage, isotopic analyses, sediment, organic carbon

Seagrass meadows are one of the most productive ecosystems and play an important role as carbon reservoirs, storing large amount of organic carbon in the sediments. Estuaries are considered to be a net source of atmospheric CO₂ due to the mineralization of terrestrial carbon but recent studies demonstrated that seagrass meadows in estuaries can be sinks for atmospheric CO₂. The flow of organic and inorganic carbon derived from multiple sources regulates these processes but the knowledge about these relationships is limited. In this study, we evaluated the flow of carbon derived from multiple sources in seagrass meadows using isotopic approaches and associated the flow with the processes of both atmospheric CO₂ uptake and carbon storage in sediments. We estimated the contribution of atmospheric CO₂ to assimilated seagrass carbon by a carbon-source mixing model using radiocarbon concentrations (Δ¹⁴C). The model indicated that the seagrass assimilated 0–40% of its inorganic carbon as atmospheric CO₂. The stable isotopic signatures (δ¹³C and δ¹⁵N) of both particulate organic carbon (OC) and sedimentary OC suggested that the efficiency of OC storage in sediments would be dependent on OC derived from multiple sources. We will also present the historical changes in carbon storage using sediment core analyses.