In rapidly urbanizing areas of the Unites States, stormwater runoff is a major water quality and treatment problem because it accumulates many harmful chemicals from our homes, roads, and cities as it flows downstream. Although it this "urban stream syndrome" is known to be harmful to fish and aquatic ecosystems, the chemical make-up of urban stormwater runoff is poorly understood. This project will focus on identifying toxic chemicals in urban stormwater, focusing particularly on understanding the link between stormwater pollution and observations of mortality in the economically and culturally important adult coho salmon in the Pacific Northwest. This project will measure harmful pollutants in stormwater with the goal to better manage urban water quality and protect fish such as coho salmon. Citizen scientists will help monitor watersheds for salmon mortality as it happens, and alert project researchers to collect water and tissue samples during acute mortality events. The research group of Edward Kolodziej will work with citizen science groups, regional agencies, and the Center for Urban Waters (Tacoma, WA) to collaborate with local, regional, state, and tribal communities who are interested in protecting salmon for economic and cultural reasons. <br/><br/>Relative to well-studied urban pollutant sources such as municipal wastewater effluent, little is known about the chemical composition of urban stormwater runoff despite its importance as a major source of chemical pollutants to receiving waters. In the Pacific Northwest, an unexplained acute mortality phenomena occurs widely in urbanized watersheds where 50-100% of adult coho salmon quickly perish after urban stormwater exposure. This project will focus on characterizing the identity and quantity of novel contaminants in urban stormwater using high-resolution mass spectrometry to identify stormwater contaminants with problematic structures such as metabolic poisons that inhibit mitochondrial electron transport and induce cellular hypoxia. Water and tissue samples collected by citizen scientists will be screened using broad spectrum, suspect and non-target analyses to identify novel pollutants in urban stormwater. Chemical bioactivity will be selectively screened via in-silico receptor docking to detect novel bioactivity from high interest detections. Along with ongoing ecotoxicology efforts, selective fractionation and chemical screening will be used to identify toxicant candidates in toxicologically active samples and link toxicant chemical characteristics to typical stormwater runoff treatment systems. Project outputs will be broadly disseminated through collaboration and outreach efforts to local and regional citizen science programs. Through the project affiliation with the Center for Urban Waters, additional outreach to local, regional, state, and tribal stakeholders, many of them very interested in salmonid health for economic and cultural reasons, will occur. Project collaborations will include regional municipalities and agencies such as the Puget Sound Partnership as well as NOAA-NMFS researchers and regulators focused on the health of economically important salmon populations. Via project characterization efforts, the management of urban stormwater quality can be improved by enhanced capabilities for chemical source control and optimization of treatment technologies.<br/><br/>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.