Glacial meltwater drains into proglacial rivers where it interacts with the surrounding landscape, collecting microbial cells as it travels downstream. Characterizing the composition of the resulting microbial assemblages in
transport can inform us about intra-annual changes in meltwater flowpaths beneath the glacier as well as hydrological connectivity with proglacial areas.

In a new paper (the first one led by our PhD student Kristýna Vrbická!) we investigated how the structure of suspended microbial assemblages evolves over the course of a melt season for three proglacial catchments of the Greenland ice sheet (GrIS). Our results suggest that both glacial and proglacial hydrological processes are likely influential for the resulting assemblage structure. Specifically, the ratio of glacierized to proglacial catchment coverage and the hydrological connectivity with different habitat types seems to play a bigger role in assemblage structure than the absolute catchment size or discharge. Importantly, the interaction of stream water with corresponding non-glaciated proglacial catchments likely evolve over the course of the summer, leading to substantial changes to assemblage structure over the melt season. These results are important for hydrologists and biogeochemists using microbial cells as indicators for hydrological flow paths, which are likely to change in these sensitive landscapes with climate warming.

(This research was part of the now legendary WhatTheFlux project of summer 2018 led by our friend Jon Hawkings.)

Vrbická K, Kohler TJ, Falteisek L, Hawkings JR, Vinšová P, Bulínová M, Lamarche-Gagnon G, Hofer S, Kellerman AM, Holt AD, Cameron KA, Schön M, Wadham JL, Stibal M (2022) Catchment characteristics and seasonality control the composition of microbial assemblages exported from three outlet glaciers of the Greenland Ice Sheet. Frontiers in Microbiology 13:1035197 doi: 10.3389/fmicb.2022.1035197