Temperature differently affected methanogenic pathways and microbial communities in sub-Antarctic freshwater ecosystems

Freshwater ecosystems are responsible for an important part of the methane (CH4) emissions which likely to change with global warming. This study aims evaluate temperature-induced (from 5 20 °C) changes on microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes strait Cape Horn, Chile. We combined situ CH4 flux measurements, production rates (MPRs), gene abundance quantification analysis (metabarcoding 16S rRNA gene). Under unamended conditions, a temperature increase °C doubled MPR while was not affected. Stimulation methanogenesis by precursors as acetate H2/CO2, resulted MPRs up 127-fold 19-fold, respectively, well enrichment mcrA-carriers strikingly stronger under amendment. At low temperatures, H2/CO2-derived were considerably lower (down 160-fold lower) than acetate-derived MPRs, but contribution hydrogenotrophic increased temperature. Temperature dependence significantly higher incubations spiked H2/CO2 (c. 1.9 eV) compared or 0.8 eV). found shape total structure, that rather exhibited site-specific variability among studied lakes. However, archaeal driven amended dominance Methanobacterium H2/CO2-based Methanosarcina acetate-based incubations. also suggested importance acetogenic H2-production outcompeting hydrogenotrohic especially at further supported homoacetogen proportion microcosm communities. The combination situ-, laboratory-based measurements molecular approaches indicates pathway may become more increasing temperatures acetoclastic pathway. In continuously warming environment climate change, such issues crucial receive attention.