The biodiversity and geochemistry of cryoconite holes in Queen Maud Land, East Antarctica

Cryoconite holes are oases of microbial diversity on ice surfaces. In contrast to the Arctic, where during the summer season most cryoconite holes are ‘open’, in Antarctica they are in most cases ‘lidded’ or completely frozen throughout the whole year. Thus, they represent ideal systems for the study of microbial community assemblies as well as carbon accumulation, since individual cryoconite holes can be isolated from the atmosphere for years. Here, we use high-throughput sequencing of the 16S and 18S rRNA genes to describe the bacterial and eukaryotic community compositions in cryoconite holes and surrounding lake, snow, soil and rock samples in Queen Maud Land. We cross correlate our findings with a broad range of geochemical data including for the first 13C and 14C analyses of Antarctic cryoconites. We show that the relative abundance of bacterial taxa cluster according to sampling locations, whereas eukaryotes seem to follow a random distribution. Cryoconite holes are distinct from soils in both 13C and 14C and their isotopic composition is also different from similar samples in the Arctic. Carbon was generally low abundant (max 0.2%) and older (6-10 ky) than the surrounding soils, suggesting that the cryoconite holes are much more isolated from the atmosphere than the soils.