Abstract
Northern post-glacial lakes are significant, increasing sources of atmospheric carbon through ebullition (bubbling) of microbially-produced methane (CH(4)) from sediments. Ebullitive CH(4) flux correlates strongly with temperature, reflecting that solar radiation drives emissions. However, here we show that the slope of the temperature-CH(4) flux relationship differs spatially across two post-glacial lakes in Sweden. We compared these CH(4) emission patterns with sediment microbial (metagenomic and amplicon), isotopic, and geochemical data. The temperature-associated increase in CH(4) emissions was greater in lake middles-where methanogens were more abundant-than edges, and sediment communities were distinct between edges and middles. Microbial abundances, including those of CH(4)-cycling microorganisms and syntrophs, were predictive of porewater CH(4) concentrations. Results suggest that deeper lake regions, which currently emit less CH(4) than shallower edges, could add substantially to CH(4) emissions in a warmer Arctic and that CH(4) emission predictions may be improved by accounting for spatial variations in sediment microbiota.