Abstract
The basal zone of glaciers is characterized by physicochemical properties that are distinct from firnified ice due to strong interactions with underlying substrate and bedrock. Basal ice (BI) ecology and the roles that the microbiota play in biogeochemical cycling, weathering, and proglacial soil formation remain poorly described. We report on basal ice geochemistry, bacterial diversity (16S rRNA gene phylogeny), and inferred ecological roles at three temperate Icelandic glaciers. We sampled three physically distinct basal ice facies (stratified, dispersed, and debris bands) and found facies dependent on biological similarities and differences; basal ice character is therefore an important sampling consideration in future studies. Based on a high abundance of silicates and Fe‐containing minerals and, compared to earlier BI literature, total C was detected that could sustain the basal ice ecosystem. It was hypothesized that C‐fixing chemolithotrophic bacteria, especially Fe‐oxidisers and hydrogenotrophs, mutualistically support associated heterotrophic communities. Basal ice‐derived rRNA gene sequences corresponding to genera known to harbor hydrogenotrophic methanogens suggest that silicate comminution‐derived hydrogen can also be utilized for methanogenesis. PICRUSt‐predicted metabolism suggests that methane metabolism and C‐fixation pathways could be highly relevant in BI, indicating the importance of these metabolic routes. The nutrients and microbial communities release from melting basal ice may play an important role in promoting pioneering communities establishment and soil development in deglaciating forelands.
Highlights
Glaciers represent important ecosystems (e.g., (Anesio et al, 2009; Hodson et al, 2008; Hotaling et al, 2017))
We report on basal ice geochemistry, bacterial diversity (16S rRNA gene phylogeny), and inferred ecological roles at three temperate Icelandic glaciers
Basal ice (BI) from southern Icelandic glaciers contains a diverse community of bacteria
Summary
Glaciers represent important ecosystems (e.g., (Anesio et al, 2009; Hodson et al, 2008; Hotaling et al, 2017)). The subglacial environment has received much less attention but is thought to be important for bedrock-derived mineral substrate weathering and the release of nutrients into the proglacial environment as MicrobiologyOpen. BI inherits physical and chemical characteristics from its close interaction with the glacier substrate, which differ from those of atmospherically derived (i.e., firnified) englacial ice (Hubbard et al, 2009; Swift et al, 2018). Differences in BI physical and chemical characteristics are often interpreted to indicate formation by distinct subglacial processes (Cook et al, 2007; Hubbard & Sharp, 1995; Knight, 1997; Knight & Knight, 1994; Swift et al, 2018)
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