Controls on Nitrogen Fixation by Plankton in Aquatic Ecosystems

水生生态系统中浮游生物固氮的控制

• 批准号: 8917758
• 负责人: Robert Howarth
• 金额: $ 41.54万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-06-01 至 1994-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8917758&HistoricalAwards=false
• 关键词: Controls; Nitrogen; Fixation; Plankton; Aquatic

Nitrogen fixation rates are generally lower in estuaries and coastal marine ecosystems than in freshwater lakes; this difference is a major reason that phosphous limitation is more likely in lakes and nitrogen limitation is more likely in marine ecosystems. Two hypotheses to explain this difference are prominent in the literature: 1.) trace meals required for nitrogen fixation (molybdenum, iron) are less available in seawater than in freshwater; and 2.) nitrogen fixation is favored by anoxic microzones, and these zones are more likely in lakes because of lower turbulence and higher dissolved organic carbon concentrations. Howarth proposes to directly test these two hypotheses with ecosystem-scale experiments and observations. He will also investigate other possible interactions among physical and biogeochemical factors in regulating nitrogen fixation, such as the influence of turbulence on stratification (and therefore average light intensity) in regulating nitrogen fixation. His approach consists of mesocosm and whole-lake experiments and of ecosystem-scale observations in a diverse set of systems, including salt lakes and turbulent freshwater lakes. He will use models (conceptual, statistical, and simulation) to focus and guide the research. Howarth is a leader in the area of biogeochemistry and the facilities provided by Cornell University are outstanding.

河口的固氮率一般较低， 沿海海洋生态系统比淡水湖;这 差异是磷限制更多的主要原因 可能在湖泊和氮限制更可能在海洋 生态系统 解释这种差异的两个假设是 在文学中很突出：1）所需的微量膳食 氮固定（钼，铁）是较少可用的， 淡水中的水;（2）有利于固氮 缺氧微区，这些区域更有可能在湖泊中 因为湍流较低，溶解有机碳较高， 浓度的 Howarth建议直接测试这两个假设， 生态系统规模的实验和观察。 他还将 研究物理和化学物质之间其他可能的相互作用， 调节固氮的生物地球化学因素，例如 湍流对分层的影响（因此 平均光照强度）对固氮的调节作用。 他的方法包括中型生态系统和全湖实验 以及在不同系统中进行生态系统尺度的观测， 包括盐湖和湍流的淡水湖。 他将 使用模型（概念，统计和模拟）来集中和 指导研究。 Howarth是地球化学领域的领导者， 康奈尔大学提供的设施是一流的。