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Every spring, heavy rain and warming temperatures kickstart the annual mountain snowmelt. As this extra water moves across the landscape, soil and plants act as filters, capturing and holding onto nutrients, toxic chemicals, and whatever else they pick up along the way. 

But when water pools and flows across hard surfaces like roads and parking lots, it picks up even more toxics before heading down storm drains. Unfiltered, this stormwater runoff negatively affects the ecosystems it eventually drains into.

One of the toxic chemicals in runoff comes from vehicle tires and is killing coho salmon, leading scientists to question what other stormwater pollutants are doing to other kinds of salmon and other fish and wildlife. 

To answer this, �������� Professor of Environmental Sciences Ruth Sofield and Research Lab Technician Katie Knaub (’21, Environmental Science, Toxicology) are studying the effects of stormwater runoff on a cousin of the coho, the Chinook salmon, Oncorhynchus tshawytscha, also known as the king salmon, as it is the largest of the pacific salmon species.

Chinook salmon are a keystone species in the Pacific Northwest because they are a primary food source for other animals, including orcas. 

“There’s a lot of interest in what happens when stormwater runoff gets into the water and what it does to the animals that are in the water,” said Sofield, who is the principal investigator on this study as well as the director of Western’s Institute of Environmental Toxicology and Chemistry and chair of the Environmental Sciences Department.

Earlier this year, in the rainiest parts of April and May, Sofield and Knaub trained dozens of helpers from the Environmental Sciences and Environmental Studies departments to collect data during two sampling events in Commencement Bay near Tacoma.

Juvenile Chinook salmon were retrieved from net pens each sampling day from four locations in the bay. Students recorded the weight and length of each fish, swabbed the bodies and gills for DNA testing, and dissected and froze the fish for further research. In all, they sampled about 350 fish. 

“This was a good look at how the science is done,” said Zander Albertson, a senior instructor in the Environmental Studies Department who helped recruit students and himself participated in this fieldwork. “It showed them the labor and challenges —&�Բ�����;and fun —&�Բ�����;that fieldwork entails.” 

Over the next year, researchers will use the data collected before and after the spring storm season to look at how stormwater pollution affects the health of Chinook salmon. 

This ongoing research is a collaboration with the Puyallup Tribe of Indians, Washington Department of Fish and Wildlife, the University of Washington Tacoma, the University of Saskatchewan, the Washington Department of Ecology, and others. 

Learn more about environmental toxicology at Western at the and find related degrees in .

Jennifer Nerad covers Western's College of the Environment for the Office of University Communications. Have a great story idea? Reach out to her at neradj@wwu.edu.