Genetic functional potential displays minor importance in explaining spatial variability of methane fluxes within a Eriophorum vaginatum dominated Swedish peatland.

Microbial communities of methane (CH₄) producing methanogens and consuming methanotrophs play an important role for Earth's atmospheric CH₄ budget. Despite their global significance, knowledge on how much they control the spatial variation in CH₄ fluxes from peatlands is poorly understood. We studied variation in CH₄ producing and consuming communities in a natural peatland dominated by Eriophorum vaginatum, via a metagenomics approach using custom designed hybridization-based oligonucleotide probes to focus on taxa and functions associated with methane cycling. We hypothesized that sites with different magnitudes of methane flux are occupied by structurally and functionally different microbial communities, despite the dominance of a single vascular plant species. To investigate this, nine plant-peat mesocosms dominated by the sedge Eriophorum vaginatum, with varying vegetation coverage, were collected from a temperate natural wetland and subjected to a simulated growing season. During the simulated growing season, measurements of CH₄ emission, carbon dioxide (CO₂) exchange and δ¹³C signature of emitted CH₄ were made. Mesocosms 1 through 9 were classified into three categories according to the magnitude of CH₄ flux. Gross primary production and ecosystem respiration followed the same pattern as CH₄ fluxes, but this trend was not observed in net ecosystem exchange. We observed that genetic functional potential was of minor importance in explaining spatial variability of CH₄ fluxes with only small shifts in taxonomic community and functional genes. In addition, a higher β-diversity was observed in samples with high CH₄ emission. Among methanogens, Methanoregula, made up over 50% of the community composition. This, in combination with the remaining hydrogenotrophic methanogens matched the δ¹³C isotopic signature of emitted CH₄. However, the presence of acetoclastic and methylotrophic taxa and type I, II and Verrucomicrobia methanotrophs indicates that the microbial community holds the ability to produce and consume CH₄ in multiple ways. This is important in terms of future climate scenarios, where peatlands are expected to alter in nutrient status, hydrology, and peat biochemistry. Due to the high functional potential, we expect the community to be highly adaptive to future climate scenarios. [ABSTRACT FROM AUTHOR]