Ebullitive CH4 flux and its mitigation potential by aeration in freshwater aquaculture: Measurements and global data synthesis

Freshwater aquaculture ponds constitute one of the important anthropogenic sources of atmospheric methane (CH 4 ). Nevertheless, estimates of global CH 4 emissions from freshwater aquaculture have large uncertainties due to a lack of data from different aquaculture types. Furthermore, despite that ebullition is a major pathway of CH 4 in aquatic systems, the quantification of ebullitive CH 4 fluxes from typical freshwater aquaculture ponds has been poorly represented. Here, field measurements of CH 4 fluxes over two years were taken to quantify ebullitive CH 4 fluxes from inland freshwater fish and crab aquaculture ponds in subtropical China. Ebullitive CH 4 fluxes averaged 15.97 ± 1.57 and 11.22 ± 1.26 mg m −2 d −1 in the fish and crab ponds in the first experimental year, respectively, and were 22.86 ± 2.30 and 21.95 ± 2.19 mg m −2 d −1 in the second year. During aquaculture period, ebullition dominated the emission pathways of CH 4 , accounting for 83% and 98% of the total CH 4 emissions in the fish and crab ponds, respectively. Ebullitive CH 4 fluxes exhibited considerable spatial variations, with the lowest flux rates captured at the aeration area due to aerator-use in both the fish and crab ponds. Dissolved oxygen and dissolved organic carbon were the two primary factors that drove ebullitive CH 4 fluxes in both aquaculture ponds. By incorporating global measurement data, we further assessed the CH 4 mitigation potential of aerator use in freshwater aquaculture and revealed the dominant role of ebullition in this mitigation contribution. Together with the rice-based aquaculture, aerator use could reduce CH 4 emissions from freshwater aquaculture ponds globally by 71% and in China by 63%. • Ebullition dominates the pathways of CH 4 emissions from inland aquaculture. • Ebullitive CH 4 fluxes differ with bioturbation to sediment in aquaculture ponds. • Aerator use could reduce global inland aquaculture CH 4 emissions by 71%. • Specific area aerator use benefits the whole aquaculture pond CH 4 mitigation.