Preprints
https://doi.org/10.5194/egusphere-2024-817
https://doi.org/10.5194/egusphere-2024-817
24 Apr 2024
 | 24 Apr 2024
Status: this preprint is open for discussion.

Understanding microbial sourcing in Greenland subglacial runoff

Guillaume Lamarche-Gagnon, Marek Stibal, Alexandre M. Anesio, Jemma L. Wadham, Jon Hawkings, Lukáš Falteisek, Kristýna Vrbická, Petra Klímová, Jakub D. Žárský, Tyler J. Kohler, Elizabeth A. Bagshaw, Jade E. Hatton, Alex D. Beaton, and Jon Telling

Abstract. The microbial ecosystems that lie beneath ice sheets can impact and contribute to global biogeochemical cycles, yet remain poorly understood given the logistical challenges in directly accessing the subglacial environment. Studies instead often rely on indirect sampling of subglacial systems via the collection of meltwaters emerging from ice margins. However, the origin of exported material in these waters will change over a melt season as glacier hydrology responds to changes in surface melt. Here, we reveal trends in microbial sourcing (source environment) and assemblages in a large proglacial river in southwest Greenland by investigating three microbial datasets (16S rRNA) collected during different hydrological periods over three separate summer melt seasons. By combining microbial data with high-resolution hydrological and hydrochemical measurements, we show that changes in microbial assemblages follow changes in hydrological periods, likely influenced by variations in glacial drainage expansion inland with concomittant variations in inputs of surface melt and subglacial sediment exports. We further illustrate how relative changes in microbial assemblages can inform on the state of the glacial hydrological system, and also focus on methane-cycling populations to infer their potential distribution beneath the ice. Overall, our results highlight that timing matters when sampling proglacial rivers and we caution interpretations of exported assemblages without a good understanding of the catchment and system studied; this is especially true for larger systems which undergo more complex hydrological changes over a melt season.

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Guillaume Lamarche-Gagnon, Marek Stibal, Alexandre M. Anesio, Jemma L. Wadham, Jon Hawkings, Lukáš Falteisek, Kristýna Vrbická, Petra Klímová, Jakub D. Žárský, Tyler J. Kohler, Elizabeth A. Bagshaw, Jade E. Hatton, Alex D. Beaton, and Jon Telling

Status: open (until 14 Jun 2024)

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Guillaume Lamarche-Gagnon, Marek Stibal, Alexandre M. Anesio, Jemma L. Wadham, Jon Hawkings, Lukáš Falteisek, Kristýna Vrbická, Petra Klímová, Jakub D. Žárský, Tyler J. Kohler, Elizabeth A. Bagshaw, Jade E. Hatton, Alex D. Beaton, and Jon Telling
Guillaume Lamarche-Gagnon, Marek Stibal, Alexandre M. Anesio, Jemma L. Wadham, Jon Hawkings, Lukáš Falteisek, Kristýna Vrbická, Petra Klímová, Jakub D. Žárský, Tyler J. Kohler, Elizabeth A. Bagshaw, Jade E. Hatton, Alex D. Beaton, and Jon Telling

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Short summary
To better understand the microbial ecosystems that underlay Earth’s glaciers, studies often rely on indirect sampling of the subglacial environment via proglacial meltwater runoff. Our research in Greenland reveals that fluctuations in glacier melt can affect microbial composition in runoff, highlighting important biases often overlooked in studies of glacial runoff that might skew interpretations as to the subglacial origin of microbial communities exported within meltwaters.