Do Trace Metal Concentrations in the Upper Columbia River Affect Early Life Stage White Sturgeon?

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To understand if contaminants are associated with white sturgeon population declines, U.S. Geological Survey scientists reviewed the life history, physiology, and behavior of white sturgeon, along with recent toxicological studies and existing trace metal data for locations in the Columbia River. The analysis indicated that the highest concentrations of copper and other metals in the Columbia River were measured at the water-sediment interface, which may, along with other stressors, present a potential threat to the health of juvenile white sturgeon. 

White sturgeon hatch

White sturgeon hatch. (Credit: Joseph Warren, USGS, Western Fisheries Research Center. Public domain.)

White sturgeon (Acipenser transmontanus) populations in the Upper Columbia River (UCR) in British Columbia, Canada, and Washington, United States, are an important part of the subsistence fishing and cultural heritage of the Confederated Tribes of the Colville Reservation and the Spokane Tribe of Indians. Populations of white sturgeon in the UCR have been declining since the 1970s and models project that without the survival of fish to the age at which they can reproduce, called recruitment, the wild population in the UCR will decline to fewer than 500 fish in the next 50 years. 

Previous studies have linked sturgeon population declines to changes in habitat resulting from a combination of dam construction and historic copper smelting activities during the late 1800s through the 1900s. However, the potential effects of contaminants associated with copper smelting are not well understood. Smelting operations in the town of Trail, British Columbia, began in the 1890s, eventually developing into one of world's largest metal smelters. Until 1995, smelter slag, a black, glassy substance with high concentrations of metals, including copper, was discharged directly into the Columbia River.

To understand the role of copper on recruitment in white sturgeon, U.S. Geological Survey (USGS) scientists reviewed existing research focused on the sturgeon’s life history, physiology, behavior, and recent toxicity studies.  A geochemistry- and physiology-based model was used to determine bioavailability of metals and develop site-specific toxicity thresholds. These toxicity thresholds were compared to copper concentrations that were previously measured in the UCR at the water-sediment interface.

Early Life Stage White Sturgeon

Early life stage white sturgeon swimming in a laboratory tank. (Credit: Doug Hardesty, USGS. Public domain.)

Different early life stages of white sturgeon, including free embryos, first feeding embryos, and mixed feeding embryos, utilize interstitial spaces near the water-sediment interface, where concentrations of soluble copper reach levels as high as 24 micrograms per liter (μg copper/L). Toxicity studies reported mortality, loss of equilibrium, and immobility of sturgeon at concentrations of 1.5 to less than 16 μg copper/L and reduced swimming activity was documented at 0.88 to 7 μg copper/L. This review of life history, physiology, and behavior of white sturgeon, along with data from recent toxicity studies, indicates that metals, including copper in water at the water-sediment interface and shallow pore water, are present at concentrations toxic to early life stages in the UCR. The current review indicates that remediation and recovery efforts might improve if copper concentrations at the water-sediment interface and in shallow pore water were considered in mitigatation strategies.

This current study addresses the importance of considering multiple stressors, including contaminants and physical habitat needs of white sturgeon, when examining their recruitment and recovery in the UCR. This review is part of ongoing research to understand the effects of natural and anthropogenic changes to the environment on Department of Interior Trust species.

This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology) and the USGS Water Mission Area.