Microbial Ecology of Subglacial Environments
Detailed Environmental Description
Subglacial environments exist at the bed below ice sheets and glaciers. ~10% of land on Earth is covered by glacial ice[1] making subglacial environments a vast and important environment worthy of study. Glacial ice, while often associated with Earth’s poles, are also found well outside of polar regions[1] (Fig. 1), further signifying the expanse of subglacial environments on Earth.
The defining characteristics of subglacial environments include the complete lack of lightCite error: Invalid parameter in <ref> tag, largely anoxic conditionsCite error: Invalid parameter in <ref> tagCite error: Invalid parameter in <ref> tag, and low temperatures (around 0⁰C )Cite error: Invalid parameter in <ref> tag. Despite these common characteristics, subglacial environments are diverse in their environmental attributes. This partly derives from the diversity of Earth’s cryosphere. As suggested by the name, subglacial environments are found beneath glaciers, both alpine and outlet, but also below Earth’s massive ice sheets – the Antarctic and Greenlandic. These differing environments, while seemingly similar, are quite distinct and require their own fields of study. Glaciers only need be tens of meters thick, while ice sheets are kilometers thick.
Although defined by the presence of solid water (ice), many subglacial environments also contain liquid water – a required component for all life, including microbesCite error: Invalid parameter in <ref> tag. Below the ice of warm and polythermal glaciers high pressures result in liquid waterCite error: Invalid parameter in <ref> tag (see Fig 2.). The amount and distribution of this water can vary from saturated sediments, to localized channels, to subglacial lakesCite error: Invalid parameter in <ref> tag.
<ref> tag.In addition to liquid water, the chemical components of subglacial minerals are required for microbial life. Due to the complete lack of light mentioned above, microbial communities rely on the presence of chemical energy within minerals at the ice-sediment interface. The flow of glaciers grinds these minerals, making them more available to the present microbial communitiesCite error: Invalid parameter in <ref> tag. As a result, the minerology below glaciers and ice sheets is an important control on nutrient availability and thus community compositionCite error: Invalid parameter in <ref> tag.
