Contrasting latitudinal patterns of reservoir methane-cycling microbial communities in water and sediment

Methane (CH 4 ) emissions from reservoirs contribute significantly to global greenhouse gas budgets, yet the latitudinal patterns and drivers of methane-cycling microbial communities in reservoir ecosystems remain poorly understood. This study simultaneously investigated methanogenic and methanotrophic communities in both water and surface sediment habitats from 23 reservoirs across a latitudinal gradient (18 °N−30 °N) in southeast China. We found pronounced differences in diversity and composition of methane-cycling microbial communities between water and sediment habitats. The alpha diversity of these communities in water decreased with increasing latitude, while it increased in the sediment. Latitude and water depth explained differential trends in the diversity of methane-cycling microbial communities in the two habitats by modulating temperature differences in water and sediments and water mixing patterns in the reservoirs. In water, the diversity and composition of methane-cycling microbial communities were explained by algal biomass and dissolved oxygen, whereas in sediments, they maintained community stability and buffered environmental stresses through complex bacterial interaction networks. These findings underscore the need for habitat-specific management strategies to mitigate reservoir methane emissions in a warming climate.