Cryoconite sediments Targeted Locus (Loci)

Sampling

Biological processes on glacier surfaces affect the physical behaviour of glaciers and ice sheets and carbon and nutrient fluxes in the cryosphere. Changes in rates of biological processes are often associated with changes in diversity, yet there is little knowledge of the diversity of active microbes on glacier surfaces and its controls. We examined the microbial abundance, community structure, and the proportion of the active microbes at two contrasting surface sites located at the margin and in the interior of the Greenland ice sheet over the course of a melting season, using DNA and RNA co-extraction from the same samples, quantitative PCR and pyrosequencing of 16S rRNA and rDNA. Whereas the rDNA abundances were similar at both sites (108 109 copies g-1), the rRNA abundance was significantly higher in the interior (1010 copies g-1). Significant differences in diversity were found between the sites, with the DNA diversity significantly higher at the margin and the RNA diversity higher at the interior site. The bulk of the active communities at both sites comprised Cyanobacteria and Alpha- and Betaproteobacteria, suggesting a truncated food web structure dominated by few bacterial primary producers and decomposers. We suggest that the ice sheet margin contains a more diverse but less active assemblage of microbes while the interior harbours a less diverse but well-adapted active community. We propose that the process of community assembly at the surface of the GrIS can be understood as species sorting from a metacommunity of airborne microbes which land on the ice surface.

Method steps

1. Pipeline used: https://www.ebi.ac.uk/metagenomics/pipelines/4.1