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

调查人员将量化的变化，有氧呼吸低于污水处理厂（WWTP）在城市流的污水排放量，并比较这些速率，以社区呼吸速率定量的昼夜氧的方法。 请求的目的是测试示踪剂刃天青（Raz）的用途，刃天青在需氧细菌存在下会不可逆地转化为试卤灵（Rru），其功效尚未在城市河流中得到验证。 工作原理是，城市河流在下游相当长的一段距离内被污水处理厂流出的营养物质所淹没，从而降低了数公里的营养物质保留效率。 对溪流生态系统功能的影响，包括溪流生态系统改善人为营养负荷的能力知之甚少。这项研究将填补空白，量化污水处理厂对代谢的Wissahickon溪，位于蒙哥马利和费城县，宾夕法尼亚州的影响。 调查人员是两名职业生涯早期的科学家，他们正在开始研究生涯。 在溪流示踪剂测试期间参与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。研究人员根据昼夜氧监测获得了初步结果，表明即使在大部分基流由污水组成的溪流中，在污水排放5公里范围内，呼吸也可能高达-13 g O2 m-2 day-1。 Raz-Rru注射将允许计算瞬时有氧呼吸的独立和特定的方法。 他们建议在Wissahickon Creek的污水处理厂进行两次测试，测试的污水营养物浓度不同。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）是否抑制或增强新陈代谢，以及在什么时间尺度上。提出的实验将提供一个更好的了解代谢的空间和时间变化，与评估一种新的方法来确定代谢在城市流的额外好处。该项目的紧迫性受到他们为测量溶解氧而设置的广泛探头的控制，该探头将仅在2017年夏季和秋季部署。

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 the 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.