RAPID: Are biogeochemical responses linked to the microbial composition of a defined nutrient and microbial input to a large river?

该项目的目标是了解退役化肥厂的水输入如何影响河流水质，该化肥厂携带大量氮素(N)和独特的微生物。化肥厂的废弃物携带在高氮条件下生长良好的微生物；因此，同时添加N和独特的微生物可以增强河流中的微生物脱氮活性，并将促进对微生物群落组成和河流氮循环之间关系的理解。这是生态系统科学中的一个重要前沿，具有提高对未来生态系统结构和功能变化的机械性理解的巨大潜力。为了实现这些目标，本研究使用了两种方法。首先，将随着时间的推移测量河流水质变化和河流水微生物群落变化之间的关系，并与未受影响的河流部分进行比较。其次，为了直接测试不同的微生物种群是否对水质有不同的影响，实验室实验将比较接种了来自河流或化肥废水池的微生物对水中氮的去除。该项目的重点是具有独特明确定义的水的释放，具有不同的化学和微生物组成，这使得能够清楚地跟踪改变的N输入和微生物群落组成对河流水质的影响。这项研究将告诉我们，了解水中微生物群落组成是否有助于预测大河的水质。该项目支持研究科学家与当地市政府和流域组织之间的直接接触，以了解对水质的控制。它还为研究生和本科生提供了收集、合成和解释河流化学和微生物学数据的实践经验。为了达到项目目标，研究人员将部署一套传感器(硝酸盐和溶解氧)和自动水样采样器，并收集抓取样本，以表征河流生物地球化学和微生物群落组成的下游变化。此外，研究人员将从河流和化肥废水中过滤活的微生物细胞，并使用这些细胞来接种包含不同氮浓度的复制实验室孵化室。在野外和实验室活动中测量的响应变量包括：水化学、硝化和反硝化速率潜力、总细菌和古生物群落组成、硝化和反硝化功能基因丰度。这项工作提供了一个独特的机会，可以更好地理解大河如何在营养输入和微生物负载改变的情况下运输和转化营养物质，这是我们理解热带营养循环的一个关键差距。此外，由于硝化和反硝化速率受到不同环境因素的限制，这项工作将深入了解支持从水生生态系统中去除总氮的两个关键过程中的生物和地球化学控制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to learn how water inputs from a decommissioned fertilizer plant, which carries a large amount of nitrogen (N) and unique microorganisms, affect riverine water quality. The fertilizer plant waste carries microorganisms that grow well in high-N conditions; thus, the concurrent addition of N and unique microbes could enhance microbiological N removal activity within the river, and will advance understanding of the connections between microbial community composition and riverine nitrogen cycling. This is a significant frontier in ecosystem science with high potential to improve mechanistic understanding of future changes in ecosystem structure and function. To accomplish these goals, the research uses two approaches. First, the relationship between changes in river water quality and changes in river water microbial communities will be measured over time and compared to unaffected sections of the river. Second, in order to directly test whether different microbial populations have different effects on water quality, lab experiments will compare N removal in waters inoculated with microorganisms from either the river or fertilizer waste ponds. This project focuses on a uniquely well-defined release of water with distinct chemistry and microbial composition, which enables clear tracking of the effect of altered N input and microbial community composition on river water quality. This research will teach us whether knowing water microbial community composition helps predict water quality in a large river. This project supports direct engagement between research scientists and their local municipality and watershed organization to learn about controls on water quality. It also gives graduate and undergraduate students hands-on experience collecting, synthesizing and interpreting data on river chemistry and microbiology. To reach project goals, the researchers will deploy a suite of sensors (nitrate and dissolved oxygen) and automated water samplers, and collect grab samples to characterize downstream changes in river biogeochemistry and microbial community composition. Also, the researchers will filter live microbial cells from river and fertilizer waste water and use these cells to inoculate replicated lab incubation chambers that contain different N concentrations. Response variables measured in both field and lab activities include: water chemistry, nitrification and denitrification rate potentials, total bacterial and archaeal community composition, nitrification and denitrification functional gene abundance. This work offers a unique opportunity to better understand how large rivers transport and transform nutrients in the face of altered nutrient inputs and microbial loads, a key gap in our understanding of lotic nutrient cycling. Also, because nitrification and denitrification rates are limited by different environmental factors, the work will provide insight on biological versus geochemical controls over two key processes supporting total N removal from aquatic ecosystems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.