Sheridan 9709033 RESEARCH SUMMARY Communities of cyanobacterial species are important in diverse ecosystems because they have the capacity to convert the inert atmospheric gas nitrogen into ammonia fertilizer. These cyanobacterial communities colonize habitats in which they are exposed to high intensity ultraviolet light which is increasing in intensity due to depletion of the ultraviolet absorbing ozone layer. Studies proposed include the strategies by which these cyanobacteria adapt to ultraviolet light. The PI has presented the results of preliminary experiments that they employ ultraviolet absorbing pigments which confer protection to cell proteins from UV damage, and that communities of cyanobacteria arrange the component species such that the UV resistant species intercept UV with W sensitive species positioned in strata beneath the upper screening species. When the stressor W is removed, the community becomes disrupted resulting in severe UV damage to the enzymes responsible for nitrogen fixation. 1
