Dissertation Research: Evaluating the functional significance of microbial community composition associated with nitrogen cycling in fresh and saltwater wetlands

微生物调控着湿地生态系统中许多重要的生态过程，如氮循环。一个主要的不确定领域是微生物群落的组成是否是氮处理速率的重要决定因素，或者这些速率是否与碰巧存在的微生物分类群无关。本博士论文改进研究项目将解决这一知识缺口，同时研究气候变化对氮生物地球化学的潜在影响。具体来说，咸水入侵历史上的淡水湿地，这是海平面上升的预期后果，预计将改变微生物介导的氮循环过程，包括反硝化（DNF）和异化硝酸盐还原为铵（DNRA）。在盐水和淡水湿地之间移动土壤微生物群落的互惠移植实验将用于确定环境条件，特别是盐度，对DNF和DNRA活性率的重要性。此外，通过使用对宿主环境的迁移开放和封闭的土壤岩心，这项工作将明确测试群落组成在决定这些生物地球化学速率方面所起的作用。了解微生物群落组成与生态系统过程速率之间的关系，对于理解气候变化、土地利用变化和影响全球生态系统的其他因素的影响非常重要。研究结果也将有助于加强环境工程努力，以减轻氮污染。来自弗吉尼亚联邦大学多元化学生群体的本科生将参与这项研究的各个方面，研究结果将直接引入应用与环境微生物学的现有课程。

Microbes regulate many important ecological processes such as nitrogen cycling in wetland ecosystems. A major area of uncertainty is whether the composition of the microbial community is an important determinant of the rates at which nitrogen is processed, or if these rates are independent of which microbial taxa happen to present. This doctoral dissertation improvement research project will address this knowledge gap while simultaneously examining potential climate change impacts on nitrogen biogeochemistry. Specifically, the intrusion of saltwater into historically freshwater wetlands, an anticipated consequence of sea level rise, is expected to alter microbially-mediated nitrogen cycling processes including denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA). A reciprocal transplant experiment that moves soil microbial communities between saltwater and freshwater wetlands will be used to determine the importance of environmental conditions, especially salinity, on DNF and DNRA activity rates. Further, by using soil cores that are both open and closed to migration from the host environment this work will explicitly test what role community composition plays in determining these biogeochemical rates. Developing an understanding of the relationship between microbial community composition and rates of ecosystem processes is important for understanding the impacts of climate change, land use change, and other factors influencing ecosystems worldwide. The findings will also be useful in enhancing environmental engineering efforts to mitigate nitrogen pollution. Undergraduates from Virginia Commonwealth University's exceptionally diverse student body will be involved in all aspects of this research, and results will be brought directly into an existing course in Applied and Environmental Microbiology.