Diverse sediment microbiota shape methane emission temperature sensitivity in Arctic lakes.

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.
(© 2021. The Author(s).)