Lake Sediments From Littoral and Profundal Zones are Heterogeneous but Equivalent Sources of Methane Produced by Distinct Methanogenic Communities—A Case Study From Lake Remoray

International audienceLake ecosystems contribute significantly to atmospheric methane and are likely to becomeeven bigger methane emitters with the global spread of hypoxia/anoxia in freshwater ecosystems. Here wecharacterized the spatial heterogeneity of methane production potential, methane concentration, archeal andbacterial communities across Lake Remoray sediment during the summer period when hypoxic conditionssettle in the deepest part of the water column. It was hypothesized that methane concentration and productionwould be higher in the deeper part of the lake, our results showed that some littoral areas exhibited similar orhigher values than the deepest area. The full 16S rRNA gene sequencing dataset counted 41 OTUs affiliatedwith methanogenic species in abundances that depended more on sampling-site location than on the water depthgradient. The methanogenic co-occurrence network revealed the existence of five distinct sub-communities,suggesting the presence of different methanogenic niches across Lake Remoray. The variation in abundanceof the two larger methanogenic sub-communities was significantly related to methanogenesis potential andsediment methane concentration across-lake but further studies investigating their real activities would provideadditional insights. In a globally changing environment (temperature, eutrophication, …) a better understandingof the functional specificities and characteristics of the potential of methane cycle actors would allow us tobetter predict their future implications for greenhouse gas production and mitigation