Microbial life in supraglacial environments

Supraglacial environments occupy 11% of Earth's surface area and represent a critical interface between climate and ice. This century has brought a renewed appreciation that glacier surfaces represent a collective of diverse microbial niches which occur wherever sufficient liquid water is available to support microbial activity: Even at the microscopic scales of ice crystal boundaries within the crystalline matrices of snow or glacial ice. Within this chapter, we review the range of microbial habitats associated with snowpacks, the glacial ice photic zone, and phototrophic microbial biofilms formed by supraglacial algae or by the darkening of microbe-mineral aggregates known as cryoconite. In summary, glacier surfaces are home to surprisingly biodiverse and active microbial communities despite their low temperatures and austere conditions. Consequently, microbial communities and their processes are interposed between climate and ice and merit urgent consideration in the light of the effects of climate warming on Earth's supraglacial environments.