Contrasting effects of aeration on methane (CH4) and nitrous oxide (N2O) emissions from subtropical aquaculture ponds and implications for global warming mitigation.

[Display omitted] • Aeration in aquaculture ponds decreased CH 4 emission but increased N 2 O emission. • The annual global warming potential of the GHGs was ca. 40% less in aerated ponds. • CH 4 was the principal contributor to the annual SGWP of the ponds. • Aeration can be an effective strategy to mitigate climate impacts of aquaculture pond. The increasing number of small-hold aquaculture ponds for food production globally has raised concerns of their emission of greenhouse gases (GHGs) such as methane (CH 4) and nitrous oxide (N 2 O). Aeration is commonly applied to improve oxygen supply for the farmed animals, but it could have opposite effects on GHG emission: It may inhibit anaerobic microbial processes that produce GHGs; it may also increase water-to-air GHG exchange via physical agitation. To resolve the overall effect of aeration on GHG emissions, this study analyzed and compared the monthly CH 4 and N 2 O emissions from earthen shrimp ponds with and without aeration, in the farming period for two consecutive years, in an estuary in subtropical southeastern China. CH 4 flux was mainly influenced by water temperature and dissolved oxygen, and it was significantly higher in non-aerated pond (7.6 mg m-2h−1) than in aerated ponds (4.5 mg m-2h−1), with ebullition accounting for >90 % of the emission. Conversely, non-aerated pond had ca. 50 % lower N 2 O flux than aerated ponds, and dissolved nitrate was the main driving factor. The combined CO 2 -equivalent emission in aerated ponds (avg. 10,829 kg CO 2 -eq ha−1 yr−1) was substantially lower than that in non-aerated pond (avg. 17,627 kg CO 2 -eq ha−1 yr−1). While aeration may increase diffusive flux of GHGs via physical agitation, it remains a simple and effective management practice to decrease the overall climate impact of aquaculture ponds. [ABSTRACT FROM AUTHOR]