Microbiology of Subglacial Environments

The abundance of water at the base of glaciers and polar ice sheets forms lacustrine features and habitats in the saturated sediments of subglacial hydrological systems. Nutrients and energy sources may be made available through mineralization of stored organic matter or through glacial processes (e.g., bedrock comminution) that provide redox couples for microbial life. The logistical challenges of accessing subglacial environments has limited direct observations to a small number of locations, but microorganisms and associated microbial activities have been found in all subglacial environments examined to date (i.e., basal ice and sediment cores, subglacial lakes, and subglacial outflows at glacial margins). Molecular and biogeochemical data imply that the microbial clades common in subglacial environments are utilizing reduced iron, sulfur, and nitrogen compounds as energy sources to fuel primary production at the glacial bed. Here, we review the latest information on the diversity of subglacial environments and discuss how interactions between physical and biogeochemical processes affect microbial ecosystems and processes at the glacier bed.