Expression of Microbial Nitrification in the Stable Isotopic Systematics of Oceanic Nitrite and Nitrate

微生物硝化作用在海洋亚硝酸盐和硝酸盐稳定同位素系统学中的表达

• 批准号: 0961098
• 负责人: Karen Casciotti
• 金额: $ 72.73万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0961098&HistoricalAwards=false
• 关键词: Expression; Microbial; Nitrification; Stable; Isotopic

Closing the marine budgets of nitrate and nitrous oxide are central goals for researchers interested in nutrient-driven changes in primary productivity and climate change. With the implementation of new methods for oxygen isotopic analysis of seawater nitrate, it will be possible to construct a budget for nitrate based on its oxygen isotopic distribution that is complementary to nitrogen isotope budgets. Before we can effectively use oxygen isotopes in nitrate to inform the current understanding of the marine nitrogen cycle, we must first understand how different processes that produce (nitrification) and consume (assimilation, denitrification) nitrate affect its oxygen isotopic signature. In this study, researchers at the Woods Hole Oceanographic Institution will provide a quantitative assessment of the oxygen isotopic systematics of nitrification in the field and thus fill a key gap in our understanding of 18O variations in nitrate, nitrite, and nitrous oxide. The primary goal is to develop a quantitative prediction of the oxygen isotopic signatures of nitrite and nitrate produced during nitrification in the sea. The researchers hypothesize that oxygen isotopic fractionation during nitrification is the primary factor setting the 18O values of newly produced nitrate and nitrite. Secondly, they hypothesize that oxygen atom exchange is low where ammonia oxidation and nitrite oxidation are tightly coupled, but may increase in regions with nitrite accumulation, such as in the primary and secondary nitrite maxima. They will test these hypotheses with a series of targeted laboratory and field experiments, as well as with measurements of nitrite and nitrate isotopic distributions extending through the euphotic zone, primary nitrite maximum, and secondary nitrite maximum of the Eastern Tropical South Pacific. The results of these experiments are expected to provide fundamental information required for the interpretation of 18O isotopic signatures in nitrite, nitrate, and N2O in the context of underlying microbial processes. A better understanding of these features and the processes involved is important for quantifying new production, controls on the N budget, and N2O production in the ocean -- which should lead to a better understanding of the direct and indirect interactions among the nitrogen cycle, marine chemistry, and climate. Broader Impacts: The results of this research should be of interest to a broad research community interested in oceanic nitrogen cycling, N2O production, and climate change, as well as nitrifier physiology and biochemistry. Student training in biogeochemistry will be an important component of the activity. A female graduate student will participate throughout this project, and will learn to integrate training in culture manipulation, laboratory and field-going research, as well as isotopic and data acquisition and analysis. There will also be opportunities for undergraduate students, including ones from under-represented minority groups, to become involved.

关闭硝酸盐和一氧化二氮的海洋预算是对初级生产力和气候变化的营养驱动变化感兴趣的研究人员的中心目标。随着海水硝酸盐氧同位素分析新方法的实施，将有可能根据硝酸盐的氧同位素分布来构建硝酸盐预算，这与氮同位素预算相辅相成。在我们能够有效地利用硝酸盐中的氧同位素来了解目前对海洋氮循环的理解之前，我们必须首先了解产生（硝化）和消耗（同化，反硝化）硝酸盐的不同过程如何影响其氧同位素特征。在这项研究中，研究人员在伍兹霍尔海洋研究所将提供一个定量评估的氧同位素系统的硝化作用在该领域，从而填补了一个关键的空白，我们的理解18 O的变化，硝酸盐，亚硝酸盐和一氧化二氮。主要目标是开发一个定量预测的氧同位素的亚硝酸盐和硝酸盐的签名在海洋硝化过程中产生的。研究人员假设，硝化过程中的氧同位素分馏是设定新产生的硝酸盐和亚硝酸盐的18 O值的主要因素。其次，他们假设，在氨氧化和亚硝酸盐氧化紧密耦合的地方，氧原子交换较低，但在亚硝酸盐积累的区域，如初级和次级亚硝酸盐最大值，氧原子交换可能会增加。 他们将通过一系列有针对性的实验室和现场实验，以及通过透光区延伸的亚硝酸盐和硝酸盐同位素分布的测量，初级亚硝酸盐最大值和次级亚硝酸盐最大值的东热带南太平洋来测试这些假设。这些实验的结果，预计将提供所需的基本信息的18 O同位素的签名在亚硝酸盐，硝酸盐，和N2 O的背景下，潜在的微生物过程的解释。更好地了解这些功能和所涉及的过程是重要的量化新的生产，控制N预算，和N2 O生产在海洋中-这应该导致更好地了解氮循环，海洋化学和气候之间的直接和间接的相互作用。更广泛的影响： 这项研究的结果应该是感兴趣的海洋氮循环，N2 O生产，气候变化，以及硝化细菌的生理和生物化学感兴趣的广泛的研究社区。对学生进行地球化学方面的培训将是该活动的重要组成部分。一名女研究生将参与整个项目，并将学习如何将培养操作、实验室和实地研究以及同位素和数据采集与分析方面的培训结合起来。本科生，包括来自代表性不足的少数群体的学生也将有机会参与其中。