Carbon dioxide and methane fluxes from mariculture ponds: The potential of sediment improvers to reduce carbon emissions.

The CO and CH fluxes across the water-air interface were determined in two groups of swimming crab (Portunus trituberculatus)-ridgetail white prawn (Exopalaemon carinicauda) polyculture ponds. One group of ponds with sediment improver application were referred to as SAPs, and the other group receiving no sediment improver were as NSPs. During the farming season, both the SAPs and NSPs acted as CO sinks and CH sources. The cumulative CO-C fluxes from the SAPs and NSPs were -26.78 and -23.49 g m, respectively, and the cumulative CH-C emissions from the SAPs and NSPs were 0.24 and 0.28 g m, respectively. CO fluxes were significantly related to net primary production and water pH, and CH fluxes were mainly regulated by water temperature during the farming season. The application of the oxidation-based sediment improver had a positive effect on reducing the CH emissions across the water-air interface but had no effect on CO fluxes. The sediment improver reduced the organic matter contents and improved the sediment pH and redox potential, which may have facilitated a decrease in CH production in the sediment. The CO produced through the oxidation of organic material in the sediment may have been absorbed by strong photosynthesis, resulting in a nonsignificant difference in CO fluxes between the SAPs and NSPs. The results indicated that the application of sediment improvers in coastal polyculture ponds can reduce carbon emissions, especially CH emissions, during the farming period and could help mitigate global warming with regard to the sustained-flux global warming potential (SGWP) and sustained-flux global cooling potential (SGCP) models over a 20-year time horizon. Future studies on the CO and CH production rates of the sediment and the related microbial community could improve our understanding of the effect mechanism of the application of sediment improvers on CO and CH emissions from mariculture ponds.