Lateral variations and vertical structure of the microbial methane cycle in the sediment of Lake Onego (Russia)

ABSTRACTThe significance of methane production by lakes to the global production of greenhouse gas is well acknowledged while underlying processes sustaining the lacustrine methane budget remain largely unknown. We coupled biogeochemical data to functional and phylogenetic analyses to understand how sedimentary parameters characterize the methane cycle vertically and horizontally in the ice-covered bay of the second largest lake in Europe, Lake Onego, Russia. Our results support a heterogeneous winter methane cycle, with higher production and oxidation closest to riverine inputs. Close to the river mouth, the largest numbers of copies of methane-related functional genes pmoA and mcrA were associated with a specific functional community, and methane production potential exceeded oxidation, resulting in 6–10 times higher methane fluxes than in the rest of the bay. The elevated fluxes arise from the spatial differences in quantity and type (lacustrine versus riverine sources) of organic matter. More homogene...