Autumn bloom of antarctic pack-ice algae.

An autumn bloom of sea-ice algae was observed from February to June of 1992 within the upper 0.4 meter of multiyear ice in the Western Weddell Sea, Antarctica. The bloom was reliant on the freezing of porous areas within the ice that initiated a vertical exchange of nutrient-depleted brine with nutrient-rich seawater. This replenishment of nutrients to the algal community allowed the net production of 1760 milligrams of carbon and 200 milligrams of nitrogen per square meter of ice. The location of this autumn bloom is unlike that of spring blooms previously observed in both polar regions.

Perennial Antarctic lake ice: an oasis for life in a polar desert.

The permanent ice covers of Antarctic lakes in the McMurdo Dry Valleys develop liquid water inclusions in response to solar heating of internal aeolian-derived sediments. The ice sediment particles serve as nutrient (inorganic and organic)-enriched microzones for the establishment of a physiologically and ecologically complex microbial consortium capable of contemporaneous photosynthesis, nitrogen fixation, and decomposition. The consortium is capable of physically and chemically establishing and modifying a relatively nutrient- and organic matter-enriched microbial "oasis" embedded in the lake ice cover.

Semipurification and ice recrystallization inhibition activity of ice-active substances associated with Antarctic photosynthetic organisms.

Ice-active substances (IASs), i.e., macromolecular substances that modify the shape of growing ice crystals, were previously found to be associated with various terrestrial and aquatic photosynthetic organisms from Antarctica, but their chemical nature and function are unknown. In this study, we used the ice-binding properties of the IASs to semipurify IASs from a cyanobacterial mat, a eukaryotic green alga (Prasiola sp.), and a moss (Bryum sp.) and examined the ice recrystallization inhibition (RI) activities of the semipure materials. The semipure materials contain both protein and carbohydrate in which the carbohydrate accounted for 73, 52, and 37%, respectively, of the total carbohydrate + protein. The IASs had RI activity at concentrations of 1.4, 0.05, and 0.01 microg ml-1, respectively. RI activity was greatly reduced by heat treatment, suggesting that the IASs inhibit recrystallization through a specific interaction with ice. These results raise the possibility that the IASs increase freezing tolerance of their respective organisms by preventing the recrystallization of ice.