Biogeographical drivers of supraglacial microbial communities

Pigment-producing microorganisms are prevalent on glacier surfaces, decreasing the snow and ice albedo. This impacts the absorption of solar radiation and accelerates rates of glacier surface melting. Studying the glacier surface ecosystem is important to understand the effects of anthropogenic climate change, and to further our knowledge of how glacier-dwelling organisms and their evolution impact downstream ecosystems. Recent studies have revealed links between habitat type, seasonality, physicochemical characteristics and the microbial composition of the supraglacial environment. However, these studies are limited in number, time points and locations. Thus, global drivers of supraglacial microbial community composition remain unknown. To fill this gap, we used data produced by our team over the last five years, as well as gathered from public repositories, to investigate the prokaryotic and eukaryotic composition of supraglacial environments worldwide.

We used 18S and 16S rRNA gene amplicon sequencing to study the microbial composition and diversity of more than eight hundred surface snow, ice and cryoconite samples from glaciers and snowfields all over the world, including Arctic, Antarctic and temperate glaciers. Results reveal a worldwide core microbiome specific to this environment, composed of generalist, freshwater and cold-adapted taxa. Distance-decay and latitudinal patterns can be identified, but key factors in determining microbial community diversity and composition rest on local to regional biogeographical scales. Habitat biology shows different responses to biogeographical drivers, likely influenced by their structure: cryoconite communities present a higher distance-decay and location specialization than snow and ice communities. In addition, communities of prokaryotes are less location-specific than those of eukaryotes. This study highlights the need for further investigation into the drivers of microbial dissemination onto glaciers and their response to local biogeography.