Devon Ice Cap microbiology

Ice formed in the subglacial environment can contain some of the highest concentrations of solutes, nutrients, and microbes found in glacier systems. Upon glacial melt, these materials are released to downstream freshwater and marine ecosystems and glacier forefields. Despite the potential ecological importance of basal ice, our understanding of its biogeochemical characteristics, and their spatial and temporal variability, remains limited. We hypothesize that the basal thermal regime of glaciers is a dominant control on subglacial biogeochemistry because it influences the degree to which glaciers mobilize material from the underlying substrate and controls the nature and extent of biogeochemical activity that occurs at glacier beds. Here, we characterize the solutes, nutrients, and microbes found in the basal regions of a cold-based glacier and three polythermal glaciers and compare them to those found in overlying glacier ice. Compared to its parent glacier ice, basal ice from polythermal glaciers was consistently enriched in major ions, dissolved organic matter (including a specific fraction of humic-like fluorescent material), and microbes, and occasionally enriched in dissolved phosphorus and reduced nitrogen (NH4+) and in a second dissolved component of humic-like fluorescent material. In contrast, the biogeochemistry of basal ice from the cold-based glacier was remarkably similar to that of its parent glacier ice. Although basal ice from the cold-based glacier may have acquired some inorganic and organic nutrients from the underlying substrate, it did not appear to contain significant amounts of either solutes or microbes derived from the glacier bed. These findings suggest that a glacier's basal thermal regime can play an important role in determining the mix of solutes, nutrients, and microbes that are acquired from subglacial substrates and/or produced in situ.