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

氮是藻类和其他水生植物必需的营养物质。一些被称为蓝藻的藻类可以在固氮过程中利用大气中的氮。然而，我们对在未受干扰的流域，如在锯齿山（ID）的荒野地区发现的那些流域，氮固定发生在哪里或是否发生知之甚少。在这些流域，温度和养分（氮和磷）浓度可能相互作用，控制固氮的速率和位置。在全球变暖导致水温升高和人为干扰造成水污染的情况下，了解这些因素如何控制固氮尤为重要。在我前三年的研究中，我专注于Sawtooth山湖泊和溪流中固氮的位置和营养控制。我现在建议使用溪边实验来测试温度和养分如何影响固氮速率。蓝藻的反应将在3、21和42天后进行测量，以检查对营养和温度变化的短期和长期反应。该实验将为全球变暖如何影响水生生态系统的固氮提供洞见。作为该项目的一部分，有关温度对水生生态系统影响的公开演讲将在林务局的篝火讲座中进行，并作为面向高中生的教育网络海报。

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.