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Category: Environmental Microbiology
Cryospheric Environments in Polar Regions (Glaciers and Ice Sheets, Sea Ice, and Ice Shelves), Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817183/9781555816049_Chap11-1.gif /docserver/preview/fulltext/10.1128/9781555817183/9781555816049_Chap11-2.gifAbstract:
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.
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Cryoconite holes, John Evans Glacier, Nunavut, Canadian High Arctic. (a) Cryoconite with frozen lid. (b) Partially open cryoconite. (c) Open cryoconite. (d) Transition zone from individual cryoconite holes to broader zones of debris-covered surficial ice. (Photo credit: M. Skidmore.)
Cryoconite holes, John Evans Glacier, Nunavut, Canadian High Arctic. (a) Cryoconite with frozen lid. (b) Partially open cryoconite. (c) Open cryoconite. (d) Transition zone from individual cryoconite holes to broader zones of debris-covered surficial ice. (Photo credit: M. Skidmore.)
Subglacial stream sampling, John Evans Glacier, Nunavut, Canadian High Arctic. (Photo credit: M. Skidmore.)
Subglacial stream sampling, John Evans Glacier, Nunavut, Canadian High Arctic. (Photo credit: M. Skidmore.)
Taylor Glacier, Antarctica. (a) Debris-rich basal ice outcrops on northern margin. (b) Tunnel to access debris-rich ice. (c) Cutting a vertical profile into the debris-rich ice in the ice tunnel. (Photo credits: panels a and b, M. Skidmore; panel c, B. Christner.)
Taylor Glacier, Antarctica. (a) Debris-rich basal ice outcrops on northern margin. (b) Tunnel to access debris-rich ice. (c) Cutting a vertical profile into the debris-rich ice in the ice tunnel. (Photo credits: panels a and b, M. Skidmore; panel c, B. Christner.)
(Left) Scanning electron microscopy image of the brine channels system in columnar sea ice made visible by filling the system with epoxy resin under a vacuum. (Right) In situ microscopic images of (a) ice crystals and brine pockets and (b) detail of a brine pocket in panel a that harbors bacteria stained with the blue DNA stain 4′,6-diamidino-2-phenylindole in panel c. (Left image from Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; reprinted from Mock and Junge [2007] with permission of the publisher. Right images adapted from Junge et al. [2001] with permission of the publisher.)
(Left) Scanning electron microscopy image of the brine channels system in columnar sea ice made visible by filling the system with epoxy resin under a vacuum. (Right) In situ microscopic images of (a) ice crystals and brine pockets and (b) detail of a brine pocket in panel a that harbors bacteria stained with the blue DNA stain 4′,6-diamidino-2-phenylindole in panel c. (Left image from Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; reprinted from Mock and Junge [2007] with permission of the publisher. Right images adapted from Junge et al. [2001] with permission of the publisher.)
Vertical gradients of temperature, salt content, brine volume, and irradiance (Io) through sea ice. These general patterns may vary due to changes in temperature. (Adapted from Mock and Junge [2007] with permission of the publisher.)
Vertical gradients of temperature, salt content, brine volume, and irradiance (Io) through sea ice. These general patterns may vary due to changes in temperature. (Adapted from Mock and Junge [2007] with permission of the publisher.)
Network of supraglacial lakes and ponds on the McMurdo Ice Shelf near Bratina Island, Antarctica. (Photo credit: A. Jungblut.)
Network of supraglacial lakes and ponds on the McMurdo Ice Shelf near Bratina Island, Antarctica. (Photo credit: A. Jungblut.)
Highly pigmented cyanobacteria-dominated microbial mats from a supraglacial pond on the McMurdo Ice Shelf, Antarctica. (Photo credit: A. Jungblut.)
Highly pigmented cyanobacteria-dominated microbial mats from a supraglacial pond on the McMurdo Ice Shelf, Antarctica. (Photo credit: A. Jungblut.)