DISSERTATION RESEARCH Temperature and Nutrient Control of Cyanobacterial Nitrogen Fixation in Subalpine Drainages: a mesocosm Experiment

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Nitrogen is an essential nutrient for algae and other aquatic plants. Some algae, called cyanobacteria, can use nitrogen from the atmosphere in a process called nitrogen fixation. However, we know very little about where or even if nitrogen fixation occurs in undisturbed watersheds such as those found in wilderness areas of the Sawtooth Mountains (ID). In these watersheds, temperature and nutrient (nitrogen and phosphorus) concentrations may interact to control rates and location of nitrogen fixation. Understanding how these factors control nitrogen fixation is particularly important as global warming increases water temperatures and human disturbances create water pollution. During my first three years of research I focused on the location and nutrient control of nitrogen fixation in Sawtooth Mountain lakes and streams. I now propose to use stream-side experiments to test how temperature and nutrients influence nitrogen fixation rates. Cyanobacteria responses will be measured after 3, 21, and 42 days to examine both short-term and long-term responses to nutrient and temperature alterations. This experiment will provide insight into how global warming may affect nitrogen fixation in aquatic ecosystems. As part of this project, public presentations about the effects of temperature on aquatic ecosystems will be made at Forest Service campfire lectures and as an educational web-based poster directed at high-school students.