Japan Geoscience Union Meeting 2025

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[J] Oral

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

[A-CG51] Coastal Ecosystems-2. Coral reefs, seagrass and macroalgal beds, and mangroves

Wed. May 28, 2025 1:45 PM - 3:15 PM Exhibition Hall Special Setting (3) (Exhibition Hall 7&8, Makuhari Messe)

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

2:30 PM - 2:45 PM

[ACG51-04] Evaluating Carbon Fixation and Dissolved Organic Carbon Release in Four Subtropical Macroalgae Species

*Chin-Chang Hung1 (1.National Sun Yat-sen University)

Keywords:carbon fixation, macroalgae, seaweed, dissolved organic carbon

Macroalgae play a crucial role in coastal carbon sequestration by converting inorganic carbon into particulate organic carbon (POC) and dissolved organic carbon (DOC). However, the extent of DOC release varies among species and environmental conditions. This study examines the growth rate, carbon fixation potential, and DOC release of Gracilaria tenuistipitata, Gracilaria coronopifolia, Sarcodia suae, and Agardhiella subulata under different salinity and cultivation conditions. The results indicate that G. tenuistipitata exhibits optimal growth (2.43 ± 0.12% /d) at salinity 10-15 with a carbon fixation rate of 961.7 ± 40.5 mgC /m² /d¹, while G. coronopifolia thrives at salinity 32 (2.78 ± 0.2% /d) with a fixation rate of 1218.5 ± 39.3 mgC /m² /d. The DOC release of G. tenuistipitata and G. coronopifolia accounts for 13% and 18% of total carbon fixation, respectively. Similarly, S. suae and A. subulata, cultivated in large tanks, exhibit carbon fixation rates of 3.07 gC /m² /d and 5.56 gC /m² /d, with DOC contributions of 13.4% and 6.6%, respectively. These findings highlight species-specific differences in DOC release and emphasize the need for further investigation into environmental factors, such as temperature, nutrient availability, and microbial interactions, that influence macroalgal carbon cycling. Understanding these mechanisms is essential for optimizing macroalgae-based carbon sequestration strategies.