DISSERTATION RESEARCH: Effects of urbanization and climate change on denitrifier community structure and function

人类福祉在很大程度上依赖于水净化和养分循环等生态系统服务。反过来，许多这些自然服务依赖于地球上最丰富、最多样化的生物群体所进行的反应。微生物。对于人类驱动因素如何影响微生物群落的结构和功能，我们所知甚少。为了帮助解决这一研究缺口，该项目将涉及一系列实验，以探索城市化和气候变化如何影响溪流中的反硝化细菌（反硝化菌）群落。反硝化菌是唯一能够永久去除生态系统中活性氮(N)的生物。水体中活性氮过多会导致有害藻华和局部缺氧等严重的水质问题。因此，河流中的反硝化物提供了重要的生态系统服务。这个项目吗?S的目标是通过实验确定与流域城市化和气候变化相关的多重压力是否以及如何影响河流反硝化菌群落结构和功能。这些压力源包括污染物和营养物质浓度的增加，以及温度的升高。为了实现这一目标，来自八个不同研究流的微生物群落将受到化学处理（重金属、盐和营养物）的组合，并在三种温度（28、38和48ºC）中的一种下孵育。在孵育期间将测量N的去除量，并使用分子指纹图谱方法对孵育前后的反硝化菌群落组成进行表征。项目结果将用于解决1)城市化和气候变化是否可能改变反硝化菌群落结构，2)反硝化菌群落结构的变化是否可能增加或减少反硝化率，以及3)压力因素之间的相互作用是相加的还是协同的。此外，通过从不同程度的流域城市化的研究溪流中提取群落，实验结果将用于推断城市与森林溪流中反硝化菌群落和反硝化率对进一步的环境退化是否更敏感。大多数关于河流的知识来自于对未受干扰的河流的研究，但美国大多数河流都受到人类活动的严重影响。最近，针对城市河流中氮循环的研究激增，但这项工作在很大程度上忽略了微生物群落介导的氮转化。通过探索城市化和气候变化对河流反硝化菌群落的影响，拟议项目的研究结果将为反硝化（N循环的重要组成部分）带来新的见解。该项目可以提供与河流管理和恢复工作相关的信息。更广泛的影响还包括指导学生。该博士生的论文研究将被纳入与当地一名高中教师共同开发的关于人类对水生生态系统影响的高中环境科学课程。项目的研究结果还将通过在同行评议的期刊上发表书面出版物和在国家会议上作口头报告的方式向更广泛的科学界传播。

Human welfare depends heavily on ecosystem services like water purification and nutrient cycling. Many of these natural services, in turn, rely on reactions performed by the most abundant and diverse group of organisms on Earth ? microbes. Remarkably little is known about how human drivers affect the structure and function of microbial communities. To help address this research gap, this project will involve a series of experiments to explore how urbanization and climate change may affect denitrifying bacteria (denitrifier) communities in streams. Denitrifiers are the only organisms that can permanently remove reactive nitrogen (N) from ecosystems. Too much reactive N in water bodies leads to serious water quality problems like harmful algal blooms and regional hypoxia. Denitrifiers in streams, therefore, provide an important ecosystem service. The project?s objective is to experimentally determine if and how multiple stressors commonly associated with watershed urbanization and climate change affect stream denitrifier community structure and function. These stressors include increased pollutant and nutrient concentrations, as well as higher temperatures. To meet this objective, microbial communities from eight different study streams will be subjected to combinations of chemical treatments (heavy metals, salt, and nutrients), and incubated at one of three temperatures (28, 38, and 48ºC). The amount of N removed will be measured over the incubation period and denitrifier community composition before and after incubation will be characterized by using molecular fingerprinting methods. Project results will be used to address whether 1) urbanization and climate change are likely to change denitrifier community structure, 2) changes to denitrifier community structure are likely to increase or decrease denitrification rates, and 3) interactions among stressors are additive or synergistic. Furthermore, by taking communities from study streams with various degrees of watershed urbanization, experiment results will be used to draw inferences on whether denitrifier communities and denitrification rates in urban versus forested streams are more or less sensitive to further environmental degradation. Most knowledge of streams comes from studying undisturbed streams, but the majority of U.S. streams are heavily impacted by human activity. Recently, there has been an explosion of research targeting N cycling in urban streams, but this work has largely ignored the microbial communities mediating N transformations. Findings from the proposed project will lead to new insights on denitrification, an important component of the N cycle, by exploring effects of urbanization and climate change on stream denitrifier communities. The project may provide information relevant to stream management and restoration efforts. Broader impacts will also include mentoring students. The doctoral student's dissertation research is being incorporated into the high school environmental science curriculum on human impacts on aquatic ecosystems being developed with a local high school teacher. Project findings will also be disseminated to the broader scientific community by written publications in peer reviewed journals and oral presentations at national conferences.