Supraglacial bacterial community structures vary across the Greenland ice sheet

Abstract

The composition and spatial variability of microbial communities that reside within the extensive (>200 000 km(2)) biologically active area encompassing the Greenland ice sheet (GrIS) is hypothesized to be variable. We examined bacterial communities from cryoconite debris and surface ice across the GrIS, using sequence analysis and quantitative PCR of 16S rRNA genes from co-extracted DNA and RNA. Communities were found to differ across the ice sheet, with 82.8% of the total calculated variation attributed to spatial distribution on a scale of tens of kilometers 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 the sampled surface type (ice versus cryoconite) did not contribute heavily towards community dissimilarities (2.3% of total variability calculated). The majority of dissimilarities found between cryoconite 16S rRNA gene amplicons from DNA and RNA 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 are spatially variable active communities that are likely influenced by localized biological inputs and physicochemical conditions.

Dark ice dynamics of the south-west Greenland Ice Sheet

“…This produces water-filled cryoconite holes with a floor of biologically active sediment (Gribbon, 1979;Cook et al, 2016). These holes range from a few centimetres to several metres in diameter and depth (MacDonell and Fitzsimons, 2008), can cover a large part of the ablation zone (Hodson et al, 2008) and have been observed to occur in the south-west region of the GrIS (Stibal et al, , 2015Cook et al, 2012;Chandler et al, 2015;Cameron et al, 2016). Hole formation increases the albedo relative to dispersed cryoconite by sequestering the lowalbedo cryoconite from the ice surface at depth, resulting in a hemispheric albedo increase that will be further enhanced by specular reflection when covered by a reflective layer of meltwater (Bøggild et al, 2010).…”

Ecological Modeling of the Supraglacial Ecosystem: A Process-based Perspective

“…Microbial cells deposited with snow may remain on the ice surface after the snow has melted and become part of the surface ice community, or they can be flushed from the ice sheet surface with meltwater (Cameron et al, 2015). Bare ice is exposed seasonally around the margins of the ice sheet and hosts a high abundance of algae (Uetake et al, 2010;Yallop et al, 2012) and other microorganisms (Stibal et al, 2015a;Cameron et al, 2016). The algae are important primary producers in the ecosystem and may contribute to surface melting via darkening the ice due to pigment production Yallop et al, 2012).…”

“…Abundance of other, mostly heterotrophic, microbes in surface ice has been found to correlate with dust concentration (Stibal et al, 2015a). Cryoconite, usually concentrated in cryoconite holes , hosts diverse and highly active microbial communities that consist of photoautotrophic cyanobacteria and a range of heterotrophic bacteria (Cameron et al, 2012(Cameron et al, , 2016Stibal et al, 2012bStibal et al, , 2015bEdwards et al, 2014;Uetake et al, 2016). Cryoconite holes provide a stable and nutrient-rich habitat within the supraglacial ecosystem, and are considered hotspots of microbial activity on glacier surfaces Cook et al, 2016a).…”

“…Microbial activity in cryoconite may also contribute to surface darkening (Takeuchi et al, 2015;Musilova et al, 2016). The interconnected nature of these three habitats allows for transportation of biomass and nutrients between them over the course of an annual cycle (Cameron et al, 2016).…”

“…GrIS supraglacial ecosystem (Edwards et al, 2014;Stibal et al, 2015b;Cameron et al, 2016). Direct measurements of W are challenging; however, first successful attempts from an Arctic glacier showed a cell flux of 10 7 cells per m 2 per day (Irvine-Fynn et al, 2012).…”