DISSERTATION RESEARCH: Pulsed and Pressed: the Interactive Effects of Disturbance Intensity and Complex Chemical Exposure on the Productivity of Urban Stream Ecosystems

城市景观中的溪流可能会受到洪水增加的负面影响，因为洪水来自不透水的表面，以及从这些表面冲洗出来的营养物质和污染物的暴露增加，这些污染物可能来自不充分的废水处理系统。了解这些不同因素在限制城市河流的生产力和健康方面的个别贡献，对于理解土地利用变化的影响很重要，但很难确定，因为它们可能同时发生。该项目将利用受控制的实验河道来分离与高流量和增加的污染物暴露有关的物理干扰如何影响河流生态系统的生产力。在小溪中，几乎所有的生产力都与生活在河床上的生物有关。河床的稳定性或对扰动的敏感性各不相同，这主要是由于河床物质的混合，包括沉积物和岩石的大小。研究人员将比较实验河道中暴露于风暴流后河床群落的恢复速率和组成。试验性的处理将包括向河水中加入不同剂量的常见城市污染物，并调整河床内沉积物的大小。研究人员将培训一名来自纽约农村社区的高中生进行研究，为高中环境科学学生制定课程计划，并通过一个研究网站和专业会议吸引公众。本研究的目的是通过实验测量物理（脉冲）和化学（压力）干扰对水生生态系统生产力的独立和相互作用。研究人员将测试以下几种假设：1)更严重的干扰可能会增加生物膜对污染物暴露的敏感性，从而加剧化学应激的影响；或者2)不太严重的干扰可能通过增加生物膜中污染物的积累而加剧化学应激的影响。水化学、生物膜组成和全流代谢将在有卵石床和沙床的实验河道受到物理干扰后的整个恢复期间进行测量。

Streams in urban landscapes can be negatively impacted by increased flooding due to runoff from impervious surfaces and elevated exposures to both nutrients and pollutants that wash off of those surfaces and can be delivered from inadequate waste water treatment systems. Understanding the individual contributions of these different factors in limiting the productivity and health of urban streams is important for an understanding of the impacts of land use changes, but difficult to identify, because they can occur simultaneously. This project will make use of controlled experimental stream channels to separate how physical disturbances associated with high flows and increased contaminant exposure affect the productivity of stream ecosystems. In small streams, almost all of the productivity is associated with organisms living on the stream bed. Stream beds vary in their stability, or susceptibility to disturbance, largely due to the mixture of streambed materials including the sizes of sediments and rocks. The researchers will compare the rates of recovery and compositions of streambed communities in experimental channels following exposure to storm flows. The experimental treatments will involve different doses of common urban contaminants added to the stream water and adjusting the size of sediments within the streambed. The researchers will train a high school student from a rural community in New York in research, develop a lesson plan for high school environmental science students, and engage the public through a research website and professional meetings. The goal of this research is to experimentally measure the independent and interactive effects of physical (pulse) and chemical (press) disturbance on aquatic ecosystem productivity. The researchers will test the alternative hypotheses that: 1) more severe disturbances may exacerbate the effects of chemical stress by increasing the susceptibility of biofilms to contaminant exposure; or 2) less severe disturbance may exacerbate the effects of chemical stress by increasing the accumulation of contaminants in biofilms. Water chemistry, biofilm composition, and whole-stream metabolism will be measured throughout the recovery period following a physical disturbance in experimental stream channels with cobble beds and sand beds.