Spatial variability of supraglacial bacterial community structures across the Greenland ice sheet. Supraglacial bacterial community structures across the Greenland ice sheet

The composition and spatial variability of microbial communities that reside within the extensive (>200,000km2) biologically active area encompassing the Greenland ice sheet (GrIS) is currently unknown. We examined bacterial communities from cryoconite debris and surface ice across the GrIS, using sequence analysis and quantitative PCR of 16S genes from co-extracted rDNA and rRNA. Communities were found to differ across the ice sheet, with 82.8% of the total calculated variation being accounted for by spatial distribution on a scale of tens of kilometres separation. Amplicons related to Sphingobacteriaceae, Pseudanabaenaceae and WPS-2 accounted for the greatest portion of calculated dissimilarities. The bacterial communities of ice and cryoconite were moderately similar (global R = 0.360, p = 0.002) and surface type (ice versus cryoconite) from which communities were sampled from did not contribute heavily towards community dissimilarities (2.3% of total variability calculated). The majority of dissimilarities found between cryoconite rDNA and rRNA amplicon libraries was calculated to be the result of changes in three taxa; Pseudanabaenaceae, Sphingobacteriaceae and WPS-2, which together contributed towards 80.8 ± 12.6% of dissimilarities between samples. Bacterial communities across the GrIS should be considered as distinct, active communities that are likely influenced by localised biological inputs and physico-chemical conditions.