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

微生物调节许多重要的生态过程，如湿地生态系统中的氮循环。 不确定性的一个主要方面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存在的微生物类群无关。 本博士论文改进研究项目将解决这一知识差距，同时研究潜在的气候变化对氮素地球化学的影响。具体而言，海水入侵到历史上的淡水湿地，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）。一个相互移植实验，移动盐水和淡水湿地之间的土壤微生物群落将被用来确定环境条件，特别是盐度，对DNF和DNRA活性率的重要性。 此外，通过使用土芯，这是开放和封闭的迁移从主机环境这项工作将明确测试什么样的作用，社区组成在确定这些地球化学速率。 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了解气候变化、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的努力，以减轻氮污染。 来自弗吉尼亚联邦大学异常多样化的学生团体的本科生将参与这项研究的各个方面，结果将直接纳入应用和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.