Interactions Among Dissolved 0rganic Matter, Genetic Structure, and Denitrification in an Agriculturally-influenced Stream Ecosystem

反硝化作用是由各种细菌群进行的关键的自然环境过程。 反硝化作用去除了水生生态系统中的活性氮，对水质有重要影响。 量化控制溪流中反硝化速率的因素及其空间和时间变异性一直是一个挑战。 本研究的目的是确定在何种程度上可以解释的细菌群落的遗传结构和细菌和其他环境因素之间的相互作用，如溶解有机物的化学反硝化模式。 该项目将在美国中西部的一个农业景观中进行，那里的氮污染是一个紧迫的问题。 这项研究将结合联合收割机现代分子生物学和同位素示踪剂的最新进展来测量河流中的脱氮率。水体氮素富集是一个长期存在的环境问题，特别是在农业区。 然而，目前对溪流和河流中氮循环的认识主要是基于对氮污染程度较低的流域的研究。 通过关注富含氮的农业景观，这项研究将扩大对人类主导的生态系统中氮循环的理解。 该项目将促进对细菌群落如何与环境相互作用以产生重要生态系统功能（反硝化）的科学理解。 它还将有助于增加关于生态系统功能如何与生物多样性相关的知识，并促进跨学科研究生培训和本科生教育。

Denitrification is a critical, natural environmental process carried out by various groups of bacteria. Denitrification removes reactive nitrogen from aquatic ecosystems and has important implications for water quality. Quantifying the factors that control denitrification rates in streams, and their spatial and temporal variability, has long been a challenge. The goal of this study is to determine the extent to which patterns in denitrification can be explained by the genetic structure of bacterial communities and the interactions between bacteria and other environmental factors, such as the chemistry of dissolved organic matter. This project will be conducted in an agricultural landscape in the midwestern U.S. where nitrogen pollution is a pressing concern. The study will combine modern molecular biology with recent advances in use of isotopic tracers to measure in-stream denitrification rates. Nitrogen enrichment of aquatic ecosystems is a persistent environmental problem, particularly in agricultural areas. However, current understanding of nitrogen cycling in streams and rivers is based largely on studies in watersheds with low levels of nitrogen pollution. By focusing on a nitrogen-rich agricultural landscape, this study will expand understanding of nitrogen cycling in human-dominated ecosystems. This project will advance scientific understanding of how bacterial communities interact with the environment to produce an important ecosystem function (denitrification). It will also contribute to a growing body of knowledge addressing the question of how ecosystem function is related to biodiversity, and promote interdisciplinary graduate research training and undergraduate education.