Virtual Posters

High northern latitudes are at the leading edge of global climate change with the effects of warming already evident in the degradation of permafrost. Increased thawing of Arctic permafrost soil systems which are significant carbon sinks containing around twice the mass of atmospheric carbon pool, releases previously sequestered labile carbon. Thawing of the permafrost initiates a transition of these tundra and peat bog (mire) systems into fens (swamps). Transition to a fen state has been associated with dramatic increases in biogenic methane production and other greenhouse gases (GHGs). Initial investigations found that rising water tables which accompanied thawing was responsible for the creation of anoxic conditions favourable to microbial methane production. The exact combination of in situ ecological conditions triggering GHG flux is unknown but a significant piece in this puzzle is the structure and dynamics of the microbial communities inhabiting thawing soils. Here, 16S rRNA gene amplicon pyrosequencing is used to characterize microbial communities along a degradation gradient in Stordalen Mire (Abisko National Park, Sweden). Sampling sites and depths were selected based on geochemical data including GHG flux. Changes in microbial community structure along the degradation gradient were substantial and occurred at the high water mark. Communities observed in the thawed-waterlogged peats with positive methane flux were relatively low complexity and were dominated by a single species within the order Methanomicrobiales and two genus of Acidobacteriaceae. Microbial community richness and composition in the un-degraded permafrost peat samples with low to negative GHG flux, approached that of non-permafrost soils, but were however also dominated by Acidobacteria. Acidobacteria comprised 20% to 42% of observed OTUs in each sample with varying levels of diversity from all within the family Acidobacteriaceae, up to representatives of most subdivisions currently identified. The ubiquity of Acidobacteria indicating that members of this phylum are adapted to low energy, low nutrient, highly acidic and high water stressed environments. Findings from this survey will guide further investigations by directing spatial and temporal sample collection from the same Mire. Insights gained regarding the ecological triggers of GHG emission, identity and activity of microbes in thawing permafrost will inform emission projections, filling a gap in current climate modeling scenarios.