Toxicity of Metals to Early Life Stages of White Sturgeon (Acipenser transmontanus)
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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 not commonly studied in ecotoxicology and their vulnerability as a species to contaminants of environmental concern is not well defined. Specifically, little work has been conducted to characterize the impact of metals to white sturgeon. To date no chronic exposure studies have been conducted with embryos, fry, and/or juveniles, which are life stages often considered susceptible to pollutants. In addition, few projects have worked with this species under experimental conditions so no information exist outlining effective methods for conducting early life stage toxicity tests. Due to the decline of many sturgeon populations, and the potential contribution of metals, there is a need for information and tools that would help with the rehabilitation of the species. The first part of this thesis presents a sub-chronic field study that was conducted on the Upper Columbia River investigating the effects of liquid effluent released by Teck American Incorporated Metals Ltd., a local metallurgical facility in Trail, BC, Canada, on early life stages of white sturgeon (Chapter 2). The primary objectives of this study were to develop the logistics for future definitive studies, gain information to design and establish an artificial exposure system for experimental testing of white sturgeon early life stages, and, if possible, to evaluate the potential impact of effluent on survival and growth of early life stage white sturgeon. Based on the experience made during the conduct of these studies we successfully established a design for an exposure system (Appendix A) that was successfully used in future definitive studies (Chapter 3). These portable, self-contained, artificial flow-through exposure systems can be completely disassembled, easily transported, and set up directly in the field or in the laboratory to be used with a water source of choice (e.g. river-water, laboratory water, effluent mixtures, contaminant dilutions, etc.). The flow regime in the re-circulating exposure units can be adjusted such that it simulates fluvial conditions of interest. Each exposure chamber contains numerous screens, and inserts of varying size, allowing modifications to the exposure area and adjustment of water height. Valuable insight was also gained into white sturgeon culturing that enabled us to successfully rear early life stages under experimental conditions. Long term studies raising embryos to 60 days post hatch led to effective embryo incubation techniques and feeding regimes to transition larvae to exogenous food (Appendix B). The most effective feeding regime for transitioning larvae to exogenous food under experimental exposure conditions included 24 h feeding at approximately 2 h intervals. A combination of live brine shrimp, frozen bloodworms, and a semi-moist powder diet worked best. Furthermore, results from this study indicate that the effluent of Teck American Incorporated Metals Ltd.’s Trail facility is not toxic to white sturgeon early life stages at the dilutions studied. There were, however, limitations and deficiencies identified in the study that promoted fish mortalities and caution should be made when interpreting the results. In this study both fertilized eggs and 16 d old sturgeon larvae were successfully reared in the exposure system. The study setup permitted successful hatching of embryos with hatching rates > 80%. Fish exposed to the greatest concentration of effluent (25%) showed greater survival rates than any of the other treatments and the fry gained weight more rapidly. It is hypothesized that this might have been due to the greater amount of nutrients or other essential trace elements available in the effluent. At termination of the experiments, percent mortalities relative to initial numbers of fish were 52%, 30%, 29%, and 20% in the controls, 1%, 5%, and 25% treatments, respectively. The second part of this thesis investigated sensitivity of early life stages of white sturgeon to metals. A study is presented that established baseline toxicity data for the sub-chronic exposure of early life stages to copper, cadmium, and zinc that can be used in metal related risk assessments (Chapter 3). Embryos, larvae, and fry were exposed to increasing concentrations of dissolved copper, cadmium, and zinc for 66 d using laboratory based flow-through exposure systems. Hatching success was greater than 79% for all controls and there were no significant differences observed among treatment groups, or between treatments and controls. Chronic lethal concentrations at which 20% mortality occurred (LC20s) for Cd (1.5 µg/L), Cu (5.5 µg/L), and Zn (112 µg/L) obtained for white sturgeon in the present study were comparable to sensitive salmonid species. Based on LC50 and LC20 values for 19 and 58 d post hatch white sturgeon, the United States national ambient water quality criteria and the Canadian water quality guidelines for the protection of aquatic life that have been established for copper, cadmium, and zinc are protective of white sturgeon early life stages.
DegreeMaster of Science (M.Sc.)
DepartmentWestern College of Veterinary Medicine
SupervisorGiesy, John P.; Hecker, Markus
CommitteeJanz, David; Pietrock, Michael; Chivers, Doug
Copyright DateSeptember 2011