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

沃格曼97-14268雪藻，雪花衣藻。生长在永久的雪地上，发现于落基山脉的高山地带，那里的栖息地包括地球上发现的一些最极端的环境条件。除了在白天的冰冻温度中存活外，这种生物还在某些条件下进行光合作用，这是在自然环境中发现的可见光和紫外线-B辐射(UV-B；280-320次)的最高通量。这项拟议的研究将量化这种核生物所经历的极端微环境，并将提供有关其在这种恶劣条件下的光合作用表现的基线信息。利用各种便携式显微传感器和仪器，将在含有雪花草种群的雪地剖面上同时测量温度、光、UV-B辐射、COZ浓度和光合作用性能。光合作用将在体外通过放氧和在可变的光温条件下进行测量。通过测量I4C：O2在雪芯中的掺入，将获得固碳的确证测量。W-B对冰盖微藻种群和光合作用真实性的影响将通过在雪地上进行的排除实验来确定。这些实验将为未来研究调节这种微生物在这种极端栖息地适应和生存的分子机制奠定基础。

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.