The Snow Alga Chlamydomonas nivalis: PhotosynthesisUnder the Greatest Extremes of High Light, UV-B Radiation and Low Temperature on Earth

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Vogelman 97-14268 The snow alga, Chlamvdomonas nivalis. grows on permanent snowfields and is found in the alpine zone of the Rocky Mountairm, a habitat that consists of some of the most extreme environmental conditions found on Earth. In addition to surviving diurnal freezing temperatures, this organism photosynthesizes under some clef the highest fluxes of visible light and ultraviolet-B radiation (UV-B; 280-320 run) found in a natural environment. The proposed research will quantify microenvironmcnta1 extremes experienced by this nucroorganism and will provide baseline information on its photosynthetic performance tinder such severe conditions. Using a variety of portable microscopic sensors and instruments, simultaneous er~virontnental measurements of temperature, light, UV-B radiation, COz concentrations add of photosynthetic performance will be made across snow-deplh profiles containing C. nivalis populations. Photosynthesis will be measured in 'vitro by oxygen evolution and under conditions of variable light avid temperature. Corroborative measurements of carbon fixation will be obtained by measuring incorporation of i4C:O2 within snow cores. Effects of W-B on C. nivaIis populations and photosynthetic performance verity be determined frown We exclusion experiments conducted on the snowfields. These experiments will establish a baseline for future studies of molecular mechanisms that regulate adaptation and survival of this microorganism in this extreme habitat.