[A-CG38] Coastal Ecosystems 2. Coral reefs, seagrass and macroalgal beds, and mangroves

[ACG38-P03] DIC outwelling from the sediments of mangrove, seagrass, and tidal marsh habitats

*Kenta Watanabe¹, Ryo Sugimoto², Atsushi Kubo³, Toshimi Nakajima⁴, Tomohiro Kuwae¹ (1.Port and Airport Research Institute, 2.Fukui Prefectural University, 3.Shizuoka University, 4.The University of Tokyo)

Keywords:Blue carbon ecosystems, Carbon dynamics, Carbonate chemistry, Porewater, Radium

Blue carbon ecosystems such as mangrove forests, seagrass beds, and tidal marshes, have the function of taking up atmospheric CO₂ and storing organic carbon (OC). The creation, conservation, and restoration of these habitats are attracting attention as sinks for atmospheric CO₂. OC assimilated by the photosynthesis is decomposed via biotic and abiotic remineralization processes, a part of them being buried in the sediments over long timescale. Almost all of the decomposed carbon has been recognized to be returned to the atmosphere as CO₂. However, the decomposed carbon would be stored in water column as inorganic carbon ions depending on the carbonate chemistry in chemical reactions of remineralization processes. In this study, we investigated the outwelling of dissolved inorganic carbon (DIC) and total alkalinity (TAlk) from the sediments of mangrove, seagrass, and tidal marsh habitats. We measured a Ra radioisotope with DIC and TAlk as a chemical tracer of the porewater from the sediments. Field surveys were conducted in Fukido River estuary (Ishigaki Island) and Komuke Lagoon (Hokkaido). Our results show that substantial amount of DIC is outwelled as ions from these habitats.