Significant variability in methane emissions from (sub)tropical aquaculture ponds driven by biogeochemical and microbial processes

Aquaculture ponds are significant hotspots of methane (CH 4 ) emissions, yet the mechanisms driving CH 4 production and emissions across diverse pond types remain poorly understood. By investigating 20 aquaculture ponds with diverse culture systems in (sub)tropical southern China, we examined CH 4 emissions ( F CH 4 ) and their underlying drivers. Our results reveal substantial CH 4 emissions from (sub)tropical aquaculture ponds, with significant variations among pond types. Fish ponds exhibited the highest F CH 4 (226 ± 441 mg m −2 d −1 ), followed by shrimp ponds (68 ± 159 mg m −2 d −1 ) and crab ponds (49 ± 112 mg m −2 d −1 ). Ebullition was the dominant pathway of CH 4 emissions, accounting for over 70% of the total CH 4 flux. CH 4 emissions were collectively regulated by management practices, environmental variables, and methane-cycling microbial communities. Salinity suppressed F CH 4 by inhibiting methanogen metabolism and restructuring methanogenic community, while elevated organic substrates could offset the salinity-driven inhibitory effect. Furthermore, rising temperature could substantially stimulate CH 4 emissions, especially ebullition, with an 11% increase in F CH 4 per 1 °C rise in water temperature. This thermal sensitivity of F CH 4 was further amplified in ponds with higher organic substrates, revealing a synergistic effect between temperature and substrate availability in promoting CH 4 production. Notably, low-latitude aquaculture ponds tended to exhibit greater temperature sensitivity. Our study highlights the considerable CH 4 emission potential of (sub)tropical aquaculture ponds and identifies salinity, organic matter, and temperature as key regulators of F CH 4 . These findings provide a framework for scaling the contribution of aquaculture ponds to the global CH 4 budgets. • (Sub)tropical aquaculture ponds were hotspots of CH 4 emissions (mean: 157 mg m −2 d −1 ). • High salinity inhibited methanogens and reshaped their community, reducing CH 4 fluxes. • CH 4 evasion showed high temperature sensitivity, with a 1 °C rise raising F CH 4 by 11%. • Temperature and substrate availability exhibited a synergistic effect on CH 4 dynamics.