Environmental risk assessment of early life stages of white sturgeon: metal related issues
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Throughout North America populations of white sturgeon (Acipenser transmontanus) are threatened, in part due to poor annual recruitment. Definitive causes for this are not yet known, but the effects of contaminants are suspected to contribute. White sturgeon are exposed to a range of contaminants as they tend to inhabit industrialized river systems such as the Columbia and Fraser. White sturgeon are not commonly studied in ecotoxicology and their vulnerability as a species to contaminants of environmental concern is not well defined. To date, few exposure studies have been conducted with larvae, fry, and/or juveniles of this species; life stages often considered most susceptible to pollutants. Specifically, little work has been conducted to characterize effects of metals on white sturgeon. In the Upper Columbia River (UCR) a population of white sturgeon has been experiencing poor annual recruitment for over thirty years, and the effects of metal pollution have been hypothesized as a potential contributing factor. In particular, Teck Metals Ltd. (Teck) operates a metallurgical facility in Trail, BC, Canada that currently discharges processed effluent into the river and historically released other metal containing tailings such as slag. There are concerns that concentrations of trace-elements, such as copper, lead, cadmium, and zinc, associated with the effluent and/or slag, might have detrimental impacts on the surrounding ecosystem, including the local white sturgeon population. In 2006, a remedial investigation and feasibility study (RI/FS) was initiated in the UCR, under the oversight of the US EPA, and this project is contributing to the portion dedicated to the risk assessment of the exposure of white sturgeon to metals. The goals of this project were to develop information on toxicity of water, sediments and associated slag to help characterize sensitivity of white sturgeon to metals, and assess associated risks of metals on the population of white sturgeon in the UCR. Previous work conducted as part of a MSc degree, examined the effects of liquid effluent released by Teck on early life stages of white sturgeon. In addition, baseline information of toxicity due to sub-chronic exposure of early life stage sturgeon to copper, cadmium, and zinc, were developed. The thesis presented herein builds upon this previous work and has three major components to further characterize sensitivity of white sturgeon to metals and risk of exposure in the UCR. Specifically, a series of acute dose-response experiments were conducted with various early life stages of white sturgeon and resulting threshold values compared to water quality standards to assess protectiveness. Sensitivity of white sturgeon to metals was characterized by conducting parallel experiments with standard test species, such as rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), as well as parallel field exposures in UCR water to develop water effect ratios (WERs) and assess relative bioavailability. A second set of experiments investigated whether exposure to water downstream of the metal smelter in Trail, BC affected survival or growth of white sturgeon. Mobile laboratories were situated riverside upstream and downstream of the smelter and the effects of potential contaminants within UCR water to early life stage white sturgeon were investigated under chronic exposure conditions. The third set of experiments involved characterizing UCR sediment toxicity and potential effects to sturgeon. Results from this research indicate that early life stage white sturgeon are relatively sensitive to copper, cadmium, lead, and zinc in comparison to other fishes. Sturgeon were particularly sensitive to copper, especially during early life stage development when larvae are transitioning to exogenous food. Thresholds for effects of copper on early life stage white sturgeon (LC50’s ranged between 9 and 22 μg/L) bracket water quality criteria for the protection of aquatic life (7.9 μg/L ± 1.5). This result indicated that white sturgeon in the UCR might not be adequately protected. Environmentally relevant concentrations of metals, such as copper, found in water, sediment, or waters associated with sediment of the UCR, including pore water and overlying water, may approach or exceed water quality criteria and lethal concentration (LC) values for sturgeon. Results from the risk assessment portion of this project, however, indicated that contaminants in the water column downstream of the metal smelter at Trail did not likely affect survival of white sturgeon. Dilution of Teck effluent in the river is such that, at the major spawning site where early life stages of sturgeon are likely to be present and where the riverside experiments from the present project were conducted, there would be no toxicity expected. Contaminants associated with sediments in the UCR and their impact on survival of sturgeon is also of concern as early life stages inhabit benthic habitats, on surface sediments, or in interstitial space between stones. Analytical results from this project did indicate that UCR sediment downstream of the smelter facility were significantly greater (p < 0.01) in concentrations of trace-elements, such as copper, lead, cadmium, and zinc, relative to reference sites. However, survival of white sturgeon was not adversely affected following exposure to UCR sediments. This project provided valuable information to help assess potential causes for poor recruitment of white sturgeon in the Columbia River. Advancements were made in characterizing the effects of metals to white sturgeon. In particular, life stage-specific sensitivities were identified that could have a significant impact on current risk assessment approaches and the derivation of protective water quality standards. There are several hypotheses as to why the number of white sturgeon have been decreasing in the UCR over the last few decades, but as of yet, no definitive cause for poor recruitment has been identified. As more research is conducted, possible causes for recruitment failure can be eliminated. Based on results from this project, metals in the UCR do not appear to be contributing directly to decreased survival of early life stage sturgeon.
DegreeDoctor of Philosophy (Ph.D.)
SupervisorGiesy, John P.; Hecker, Markus
CommitteeBlakley, Barry; Niyogi, Som; Chivers, Doug; Janz, David
Copyright DateMarch 2014