Polar Cryoconite Associated Microbiota Is Dominated by Hemispheric Specialist Genera.

Jasmin L Millar,Arwyn Edwards,Ewa A Poniecka,Anne D Jungblut,Elizabeth A Bagshaw

doi:10.3389/fmicb.2021.738451

Abstract

Cryoconite holes, supraglacial depressions containing water and microbe-mineral aggregates, are known to be hotspots of microbial diversity on glacial surfaces. Cryoconite holes form in a variety of locations and conditions, which impacts both their structure and the community that inhabits them. Using high-throughput 16S and 18S rRNA gene sequencing, we have investigated the communities of a wide range of cryoconite holes from 15 locations across the Arctic and Antarctic. Around 24 bacterial and 11 eukaryotic first-rank phyla were observed in total. The various biotic niches (grazer, predator, photoautotroph, and chemotroph), are filled in every location. Significantly, there is a clear divide between the bacterial and microalgal communities of the Arctic and that of the Antarctic. We were able to determine the groups contributing to this difference and the family and genus level. Both polar regions contain a “core group” of bacteria that are present in the majority of cryoconite holes and each contribute >1% of total amplicon sequence variant (ASV) abundance. Whilst both groups contain Microbacteriaceae, the remaining members are specific to the core group of each polar region. Additionally, the microalgal communities of Arctic cryoconite holes are dominated by Chlamydomonas whereas the Antarctic cryoconite holes are dominated by Pleurastrum. Therefore cryoconite holes may be a global feature of glacier landscapes, but they are inhabited by regionally distinct microbial communities. Our results are consistent with the notion that cryoconite microbiomes are adapted to differing conditions within the cryosphere.

Highlights

Cold climate habitats are present across the globe, sustaining a surprising abundance of life above, within, and below the ice (Boetius et al, 2015)
About 4,497 distinct 16S rRNA gene amplicon sequence variant (ASV) were identified, 313 of which were shared between the Arctic and Antarctic
Around 6,865 distinct 18S rRNA gene ASVs were found, 82 of which were shared between the Arctic and Antarctic

Summary

Introduction

Cold climate habitats are present across the globe, sustaining a surprising abundance of life above, within, and below the ice (Boetius et al, 2015). On the surface of glaciers and ice sheets, particular hotspots of diversity occur when these living cells and the associated organic matter they produce accumulate. Many of the microbes present produce extracellular polymeric substances that allow them to form biofilms and increase the habitability of their surrounding environment. In cryoconite holes, these polymeric substances cause other materials such as sediment to adhere to the cells (Langford et al, 2010), forming a stabilised habitat (Langford et al, 2010; Takeuchi et al, 2010; Webster-Brown et al, 2015; Cook et al, 2016)

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