Collaborative LExEn Research on the Role of Exopolymers in Arctic Sea Ice: Habitat Alteration and Microbial Cryoprotection

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Exopolymeric substances (EPS), secreted in the form of mucous slime by aquatic microorganisms, are known to play important roles in marine ecosystems. The proposed research will investigate the potential for exopolymeric substances to alter the microstructure of the sea-ice habitat and to serve as cryoprotectants for microorganisms dwelling within ice structures. Main research goals are as follows: (1) to determine how and to what extent the pool of EPS present in sea ice may result in an alteration of the microhabitat; (2) to assess the potential role of EPS as cryoprotection; and (3) to determine the major sea-ice producers of EPS along with relevant environmental cues for bulk and specific exopolymer production. These objectives will be pursued through a combination of laboratory and field studies, including culture-based and open-air ice-growth. The role of polymers in ice desalination processes (through their effects on brine viscosity and ice permeability) and in preventing pore closure at very low temperatures will also be investigated. These findings will be compared to in-situ EPS production by bacterial and diatom communities under quasi-natural conditions. The cryoprotectant effects of EPS and their associations with highly concentrated wintertime brines will be examined directly with in-situ experimentation in the Arctic ice sheet near Barrow, Alaska. The proposed work is relevant not only to low-temperature survival strategies and their impact on the physical environment, but also in the general context of polar marine ecology and carbon cycling, radiative and other transfer properties of the polar ice cap, industrial applications in cryobiology, and the potential habitability of Jovian moons.