Cryospheric Environments in Polar Regions (Glaciers and Ice Sheets, Sea Ice, and Ice Shelves)

Abstract

This chapter focuses on glaciers and ice sheets, sea ice, and ice shelves of the polar regions, i.e., those latitudes above the Arctic and Antarctic Circles where glaciers and ice sheets cover a significant proportion of the land mass and where large expanses of the surface waters of the Arctic and Southern Oceans undergo an annual cycle of freezing and melting. This chapter further introduces sea ice as a microbial habitat and summarizes from some of the aforementioned reviews what is known to date about the abundance, activity, diversity, and ecology of prokaryotic sea-ice microorganisms. It provides a brief outline of the role of microorganisms in biogeochemical cycling of elements in sea ice. The majority of bacteria isolated from sea ice are pigmented and highly cold adapted, with some able to form gas vesicles. Possible cold-adaptation strategies revealed by whole-genome sequence analysis also include the production of cryoprotective osmolytes and exopolymers. Polar ice shelves are thick masses of ice floating on the ocean. They are formed through glacial ice and ice sheets pushing onto the sea or long-term accumulations of sea ice. Analysis of ice-shelf heterotrophic bacteria and microbial eukaryotes suggests phylogenetic affiliation with taxa from diverse environments and climatic zones ranging from Antarctica and other cryosphere habitats to temperate ecozones. Microbial investigations on polar glaciers, ice sheets, and ice shelves are still largely in their infancy, with sea-ice research being somewhat more established.