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.

河口和沿海海洋生态系统的固氮率通常低于淡水湖泊；这种差异是湖泊生态系统中更可能出现磷限制而海洋生态系统中更可能出现氮限制的主要原因。 文献中提出了两个重要的假设来解释这种差异： 1.) 海水中固氮所需的微量膳食（钼、铁）比淡水中少； 2.) 缺氧微区有利于固氮，这些微区更可能出现在湖泊中，因为湍流较低，溶解有机碳浓度较高。 豪沃斯建议通过生态系统规模的实验和观察来直接检验这两个假设。 他还将研究物理和生物地球化学因素在调节固氮过程中其他可能的相互作用，例如湍流对调节固氮过程中分层（以及平均光强度）的影响。 他的方法包括中宇宙和全湖实验以及对不同系统（包括盐湖和湍流淡水湖）的生态系统规模的观测。 他将使用模型（概念、统计和模拟）来集中和指导研究。 豪沃思在生物地球化学领域处于领先地位，康奈尔大学提供的设施非常出色。