Emerging contaminants in juvenile Chinook salmon: Patterns of exposure and implications for conservation

Efforts to recover populations of threatened Chinook salmon in the Pacific
Northwest may be hindered by exposure to contaminants in the juvenile life
stage. Here we leverage a large dataset collected by the Washington
Department of Fish and Wildlife’s Toxic Biological Observation System to
test for accumulation of 219 contaminants of emerging concern (CECs) in
juvenile Chinook salmon and identify chemicals that could be affecting
salmon physiology, behavior, or fitness at current exposure
concentrations. We also highlight results obtained from the region’s two
most urbanized watersheds, the Green/Duwamish and Puyallup/White, to
demonstrate how these data can inform decision making to protect juvenile
salmonids. We found that juvenile Chinook salmon sampled in the
Puyallup/White watersheds had the highest average concentrations of CECs,
and that six chemicals appeared to be ubiquitous and were found in all
five river systems spanning a gradient of urbanization. In the subsequent
detailed studies in the Green/Duwamish and Puyallup/White River systems,
we observed patterns in accumulation of per- and polyfluoroalkyl
substances (PFAS) that revealed regions where certain analytes could be
entering the rivers. In contrast, spatial patterns for pharmaceutical and
personal care products (PPCPs) were less clear and indicated diffuse
sources throughout the migration corridor, such as stormwater or
wastewater. We recommend these results be used to target areas for source
tracing studies for PFAS, and that future studies test for PPCP residues
in commercial fish feed. Finally, the detection of multiple emerging
contaminants in almost all composite fish samples, 11 of which exceeded
available biological effects thresholds, reinforces the global call for
green infrastructure projects that target source control and the removal
or reduction of emerging contaminants from stormwater and wastewater.