Deborah A. Duffield

Date of Award


Document Type


Degree Name

Master of Science (M.S.) in Biology



Physical Description

1 online resource (vi, 69 p.) : ill. (some col.), 1 map


California Sea Lion, Steller Sea Lion, Harbor seals, Marine mammals -- Effect of heavy metals on -- Oregon -- Pacific Coast, Marine mammals -- Effect of heavy metals on -- Washington (State) -- Pacific Coast, Marine mammals -- Mercury content -- Oregon -- Pacific Coast, Marine mammals -- Mercury content -- Washington (State) -- Pacific Coast, Mercury -- Bioaccumulation, Methylmercury -- Bioaccumulation




Muscle samples from 105 marine mammals stranded along the Oregon-Washington coasts (2002-2009) were tested for levels of total mercury by Cold Vapor Atomic Fluorescence Spectrometry. The total mercury present is predominantly in the form of highly toxic methylmercury. After normalizing muscle tissue to 75% water weight, due to variance in water content, Steller sea lions (Eumetopias jubatus) and northern elephant seals (Mirounga angustirostris) exhibited the highest mean concentrations of total mercury followed by harbor seals (Phoca vitulina), harbor porpoises (Phocoena phocoena), and California sea lions (Zalophus californianus); 0.34 ± 0.278, 0.34 ± 0.485, 0.21 ± 0.216, 0.17 ± 0.169 and 0.15 ± 0.126 mg/kg normalized weight, respectively. Mean normalized values demonstrated limited muscle methylmercury accumulation in these species in the Pacific Northwest. Normalizing muscle mercury concentrations eliminated variability from desiccation, and allowed for a clearer indication of the amount of mercury the animal accumulated before stranding. However, actual wet weight concentrations in some of the stranded carcasses were high enough to pose a risk to scavengers.


Portland State University. Dept. of Biology

Persistent Identifier