Patterns in Microbial Assemblages Exported From the Meltwater of Arctic and Sub-Arctic Glaciers

• Published in: Frontiers in Microbiology
• Main Authors: Tyler J. Kohler, Petra Vinšová, Lukáš Falteisek, Jakub D. Žárský, Jacob C. Yde, Jade E. Hatton, Jon R. Hawkings, Guillaume Lamarche-Gagnon, Eran Hood, Karen A. Cameron, Marek Stibal
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2020
• Subjects: glacial runoff; 16S rRNA gene; polar stream; biogeography; cryosphere; hydrology; Microbiology; QR1-502; Arctic; Greenland; Norway; Qeqertarsuaq; Svalbard; glaciers; Ice Sheet; Iceland; Alaska
• Online Access: https://doi.org/10.3389/fmicb.2020.00669; https://doaj.org/article/c243a8dfd1fd47359bf72b072db4bcb5

Meltwater streams connect the glacial cryosphere with downstream ecosystems. Dissolved and particulate matter exported from glacial ecosystems originates from contrasting supraglacial and subglacial environments, and exported microbial cells have the potential to serve as ecological and hydrological indicators for glacial ecosystem processes. Here, we compare exported microbial assemblages from the meltwater of 24 glaciers from six (sub)Arctic regions – the southwestern Greenland Ice Sheet, Qeqertarsuaq (Disko Island) in west Greenland, Iceland, Svalbard, western Norway, and southeast Alaska – differing in their lithology, catchment size, and climatic characteristics, to investigate spatial and environmental factors structuring exported meltwater assemblages. We found that 16S rRNA gene sequences of all samples were dominated by the phyla Proteobacteria, Bacteroidetes, and Actinobacteria, with Verrucomicrobia also common in Greenland localities. Clustered OTUs were largely composed of aerobic and anaerobic heterotrophs capable of degrading a wide variety of carbon substrates. A small number of OTUs dominated all assemblages, with the most abundant being from the genera Polaromonas, Methylophilus, and Nitrotoga. However, 16–32% of a region’s OTUs were unique to that region, and rare taxa revealed unique metabolic potentials and reflected differences between regions, such as the elevated relative abundances of sulfur oxidizers Sulfuricurvum sp. and Thiobacillus sp. at Svalbard sites. Meltwater alpha diversity showed a pronounced decrease with increasing latitude, and multivariate analyses of assemblages revealed significant regional clusters. Distance-based redundancy and correlation analyses further resolved associations between whole assemblages and individual OTUs with variables primarily corresponding with the sampled regions. Interestingly, some OTUs indicating specific metabolic processes were not strongly associated with corresponding meltwater characteristics (e.g., nitrification and inorganic nitrogen ...