Japan Geoscience Union Meeting 2023

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG41] Coastal Ecosystems 2. Coral reefs, seagrass and macroalgal beds, and mangroves

Thu. May 25, 2023 3:30 PM - 4:45 PM 102 (International Conference Hall, Makuhari Messe)

convener:Yu Umezawa(Tokyo University of Agriculture and Technology), Tomihiko Higuchi(Atmosphere and Ocean Research Institute, The University of Tokyo), Takashi Nakamura(School of Environment and Society, Tokyo Institute of Technology), Kenta Watanabe(Port and Airport Research Institute), Chairperson:Yu Umezawa(Tokyo University of Agriculture and Technology), Tomihiko Higuchi(Atmosphere and Ocean Research Institute, The University of Tokyo), Takashi Nakamura(School of Environment and Society, Tokyo Institute of Technology), Kenta Watanabe(Port and Airport Research Institute)

3:30 PM - 3:45 PM

[ACG41-06] Effects of marine macrophyte habitats including seaweed aquaculture on pCO2 and DOC variations in human-impacted coastal waters

*Kenta Watanabe1, Tatsuki Tokoro2,1, Hirotada Moki1, Tomohiro Kuwae1 (1.Port and Airport Research Institute, 2.National Institute for Environmental Studies)

Keywords:Carbon cycling, Seaweed aquaculture, Blue carbon

Carbon cycles in coastal waters are highly affected by human activities. Primary production regulate CO2 sink–source behavior in coastal waters, but the contribution of macrophyte habitats including seaweed aquaculture to coastal carbon dynamics has not been understood. We investigated the variations in pCO2, carbonate chemistry, and dissolved organic carbon (DOC) in human impacted coastal waters. We analyzed the biogeochemical drivers for the variations in these carbon parameters using generalized linear models (GLMs). Cultivated seaweed metabolism was quantified with in situ field-bag experiments. Cultivated seaweeds took up DIC and released DOC. Our GLMs estimated that macrophyte habitats contributed to the enhancement of in situ atmospheric CO2 removal during the productive period in a semi-enclosed embayment but not in an open coastal water due to the efficient water exchange. Our findings suggest that the DIC uptake rate by macrophyte habitats does not directly equate to the CO2 removal rate from atmosphere due to the time required for air–water CO2 equilibrium and the transport, implying the future needs for technological developments in tracing and modelling of macrophyte-affected water.