[A-CG35] グローバル炭素循環の観測と解析

[ACG35-10] Temporal variations of air-water carbon dioxide fluxes in tropical and subtropical clam and fishponds in Taiwan

*Veran Weerathunga¹、Li-Lian Liu¹、Fei-Ling Yuan¹、Sheng Xiang Xu¹、Kai-Jung Kao¹、Kuei-Chen Huang¹、Wei-Ming Chen¹、Wei-Jen Huang¹ (1.Department of Oceanography, National Sun Yat-sen University, Kaohsiung, Taiwan)

As aquaculture will continue to expand more on land than those in the sea, the role of these inland waters in air-water carbon dioxide (CO₂) gas exchange has gained increasing attention due to the issue of "carbon tax". However, studies focusing on CO₂ gas exchange in clam and fishponds are rare. Here, we measured the partial pressure of CO₂ at the air-water interface by deploying a home-made CO₂ buoy in three clam and three fishponds on the west coast of Taiwan for 24 hours from April 2021 to June 2022, covering three culture stages: stocking, middle, and harvesting stage. We observed both diurnal and culture stage-dependent changes in CO₂ flux. In all ponds, fluxes were stronger during the daytime due to higher wind speeds compared to nighttime. Clam ponds acted as a sink of CO₂ into the atmosphere during the stocking stage but turned into a source during the harvesting stage. Fishponds acted as a source of CO₂ during all stages, but flux became stronger when reaching the harvesting stage. Overall, clam ponds acted as a weak sink of atmospheric CO₂ (1.0 ± 18.8 mmol.m^-2.d^-1), while fishponds were a source of atmospheric CO₂ (15.9 ± 21.3 mmol.m^-2.d^-1). We suggest that management practices based on the species and culture cycle along with diurnal variations should be considered to estimate the air-water CO₂ flux in an aquaculture pond.