Distribution and abundance of methagenic and methatrophic microorganisms across European streams
Distribution et abondance de microorganismes méthagéniques et méthatrophes dans les cours d'eau européens
Résumé
Globally, streams and rivers emit a significant amount of methane, a highly potent greenhouse gas. However, little is known about stream sediment microbial communities, driving the net methane balance in these systems, especially on their distribution and composition at large spatial scales. Within the project Euro Methane we investigated the diversity and abundance of methanogenic archaea and methane-oxidizing bacteria across 16 European streams (from northern Spain to central Sweden) via 16S rRNA sequencing and qPCR. We determined environmental drivers of both abundance and community composition and explored the link to measured potential methane production and oxidation rates of the respective sediments. We found that the community composition of methane-oxidizing bacteria significantly differed among the studied streams, while methanogenic archaea were more homogeneously distributed. Beyond the overall diversity trends, indicator species for stream types were identified. Methanogenic Methanosaeta sp. and methane-oxidizing Methyloglobulus sp. increased with geographical latitude and dominated in headwater streams (orders 1-3) with high oxygen levels and high proportions of pristine land within the catchment, while methanogenic Methanomethylovorans sp. and methane-oxidizing Methylocaldum spp. were more common in larger streams (orders 4-6) with higher discharge and agricultural influence. Potential methane production rates significantly increased with abundance of methanogenic archaea, while potential methane oxidation rates did not show significant correlations with methane oxidizing bacteria, presumably due to the more diverse physiological capabilities of this microbial group. Our study represents a holistic large-scale biogeographical overview of two microbial groups to enhance our understanding of the methane cycle within a heretofore understudied ecosystem.