RAPID: Collaborative Research: Evaluating ecosystem respiration in urban streams using reactive tracer and dissolved oxygen loggers

研究人员将量化城市溪流中污水处理厂(WWTP)污水排放以下的有氧呼吸变化，并将这些速率与用Diel O2方法量化的社区呼吸速率进行比较。申请的目的是测试示踪剂瑞祖灵(RAZ)的使用情况，该示踪剂在有氧细菌存在的情况下不可逆转地转化为间苯二酚(RRU)，其有效性尚未在城市溪流中得到验证。其工作原理是，城市河流被下游相当长距离的污水处理厂排出的营养物质淹没，降低了数公里内的营养物质保持效率。对河流生态系统功能的影响，包括河流生态系统改善人为营养负荷的能力，人们知之甚少。这项研究将填补在量化污水处理厂对位于宾夕法尼亚州蒙哥马利和费城的威萨希肯溪新陈代谢影响方面的空白。研究人员是两位职业生涯早期的科学家，他们开始了自己的研究生涯。参与溪流示踪剂测试数据收集的学生志愿者将了解城市溪流中的压力源和现场表征方法。调查人员根据Diel O2监测获得了初步结果，表明即使在这条基流的大部分是污水的溪流中，在污水排放的五公里内，呼吸量也可以高达-13g O2 m-2 day-1。RAZ-RRU注射将允许一种独立的、特定于REACH的方法来计算瞬时有氧呼吸。他们建议在威萨希肯小溪上的污水处理厂进行两项测试，测试不同的流出水营养浓度。正在解决的基本研究问题是，城市系统的压力(在这种情况下，高营养浓度)是抑制还是增强新陈代谢，以及在多大的时间尺度上。建议的实验将提供更好的了解新陈代谢的时空变化，以及评估一种确定城市河流新陈代谢的新方法的额外好处。这个项目的紧迫性受控于他们为测量溶解氧而设立的广泛探测器，该探测器只会在2017年夏秋两季部署。

Investigators will quantify shifts in aerobic respiration below the effluent discharge of a wastewater treatment plant (WWTP) in an urban stream and compare these rates to community respiration rates quantified by diel oxygen methods. The request is for the purpose of testing the use of the tracer resazurin (Raz), which irreversibly transform into resorufin (Rru) in the presence of aerobic bacteria, and whose efficacy has not been verified in urban streams. The working theory is that urban streams are overwhelmed by nutrient additions through WWTP effluent for quite a distance downstream, reducing nutrient retention efficiency for kilometers. The impacts on the functioning of stream ecosystems, including the ability of stream ecosystems to ameliorate anthropogenic nutrient loading are poorly understood. This study will fill a gap in quantifying WWTP impacts on the metabolism of the Wissahickon Creek, located in Montgomery and Philadelphia counties, Pennsylvania. The investigators are two early-career scientists launching a research career. Student volunteers involved in data collection during the stream tracer test will learn about stressors in urban streams and field characterization methods.Investigators obtained preliminary results based on diel oxygen monitoring, indicating that even in this stream where a majority of baseflow is comprised of effluent, respiration can be as high as -13 g O2 m-2 day-1 within five kilometers of effluent discharge. Raz-Rru injections would allow for an independent and reach-specific method of calculating instantaneous aerobic respiration. They propose to conduct two tests at WWTPs on the Wissahickon Creek with differing effluent nutrient concentrations. The basic research question being addressed is whether the stresses of urban systems (in this case, high nutrient concentrations) inhibit or enhance metabolism, and at what temporal scale. The experiments proposed will provide a better understanding of spatial and temporal variation in metabolism, with the added benefit of evaluating a new method for determining metabolism in urban streams. The urgency of this project is controlled by their extensive probe set up for measuring dissolved oxygen, which will only be deployed in summer and fall 2017.