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Effects of conversion of coastal marshes to aquaculture ponds on sediment anaerobic CO2 production and emission in a subtropical estuary of China
Journal of Environmental Management, Volume: 338, Start page: 117813
Swansea University Author: Kam Tang
Accepted Manuscript under embargo until: 28th March 2024
The extensive conversion of carbon-rich coastal wetland to aquaculture ponds in the Asian Pacific region has caused significant changes to the sediment properties and carbon cycling. Using field sampling and incubation experiments, the sediment anaerobic CO2 production and CO2 emission flux were com...
|Published in:||Journal of Environmental Management|
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The extensive conversion of carbon-rich coastal wetland to aquaculture ponds in the Asian Pacific region has caused significant changes to the sediment properties and carbon cycling. Using field sampling and incubation experiments, the sediment anaerobic CO2 production and CO2 emission flux were compared between a brackish marsh and the nearby constructed aquaculture ponds in the Min River Estuary in southeastern China over a three-year period. Marsh sediment had a higher total carbon and lower C:N ratio than aquaculture pond sediment, suggesting the importance of marsh vegetation in supplying labile organic carbon to the sediment. Conversion to aquaculture ponds significantly decreased sediment anaerobic CO2 production rates by 69.2% compared to the brackish marsh, but increased CO2 emission, turning the CO2 sink (−490.8 ± 42.0 mg m−2 h−1 in brackish marsh) into a source (6.2 ± 3.9 mg m−2 h−1 in aquaculture pond). Clipping the marsh vegetation resulted in the highest CO2 emission flux (382.6 ± 46.7 mg m−2 h−1), highlighting the critical role of marsh vegetation in capturing and sequestering carbon. Sediment anaerobic CO2 production and CO2 uptake (in brackish marsh) and emission (in aquaculture ponds) were highest in the summer, followed by autumn, spring and winter. Redundancy analysis and structural equation modeling showed that the changes of sediment temperature, salinity and total carbon content accounted for more than 50% of the variance in CO2 production and emission. Overall, the results indicate that vegetation clearing was the main cause of change in CO2 production and emission in the land conversion, and marsh replantation should be a primary strategy to mitigate the climate impact of the aquaculture sector.
Faculty of Science and Engineering
This research was supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2020J01136, and 2022R1002006), the National Natural Science Foundation of China (Grant No. 41801070, and 41671088), the Research Grants Council of Hong Kong (Grant No. CUHK 14122521, and 14302420) and CUHK Direct Grant (Grant No. 145489489), the Minjiang Scholar Programme.