Graduate Thesis Or Dissertation
 

Assessing Mercury Levels, Health Metrics, and Immune Function in Non-stranded Male California and Steller Sea Lions in Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3197xv261

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  • California and Steller sea lions (Zalophus californianus, Eumetopias jubatus, respectively) are considered sentinel species because they have long life spans, are long-term coastal residents, feed at high trophic levels, and have large blubber stores that serve as depots for anthropogenic toxicants. There are few studies on sea lion health and immune function in apparently healthy sea lions, in part due to the Marine Mammal Protection Act, which limits research on non-stranded animals. In this study, we characterized general health, immune function, and biomarkers for mercury exposure in 48 non-stranded male California (n=29) and Steller (n=19) sea lions sampled from Bonneville Dam and Willamette Falls in the Columbia River Basin. Among California sea lions, we also investigated whether urogenital cancer lesions were associated with immune function and mercury exposure. We optimized several new health and immune assays in sea lions and also found that health and immune measurements differed between non-stranded, apparently healthy male California and Steller sea lions. California sea lions had higher packed cell volume, total protein, eosinophils, neutrophils, monocytes, bilirubin, creatine kinase, alkaline phosphatase, T4, and potassium compared to Steller sea lions while Steller sea lions had higher weight, length, albumin, c-glutamyltransferase, alanine aminotransferase, IFN gamma stimulated by Con A, and TNF alpha stimulated by Con A compared to California sea lions (Wilcoxon rank sum test, p< 0.05). Steller sea lions also had higher whisker total mercury, fur total mercury, blood total mercury, blood methylmercury, and estimated blood inorganic mercury compared to California sea lions (Wilcoxon rank sum test, p< 0.001 for all). Of the 29 California sea lions, packed cell volume, cholesterol, blood eosinophils, whisker total mercury, blood total mercury, and estimated blood inorganic mercury were associated with urogenital lesions. This study highlights new lab assays that can be used to better understand pinniped health, including physiological responses to urogenital cancer.
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  • Oregon Sea Grant
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