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Two Oregon reservoirs contaminated by different mercury sources were compared for mercury distribution in sediment and bioaccumulation by fish. The average mercury concentration in the sediment of Cottage Grove reservoir (0.67 �� 0.05 ��g/g dry wt) was higher than for Dorena Reservoir (0.12 �� 0.01 ��g/g dry wt). Sediment mercury in the main tributary of Cottage Grove Reservoir, which drains the tailing of past mercury mining activities, was ten fold higher than mercury in sediment from other reservoir tributaries with no evidence of mining. However, there were no significant differences between sediment mercury concentrations in the tributaries of the Dorena Reservoir, which has no mercury mining history within its watershed. Three fish species (largemouth bass, bluegill, crappie) from Cottage Grove Reservoir had significantly higher levels of mercury than the same species from Dorena Reservoir. These results indicated that a point source, Black Butte Mine, contributed amounts of mercury in excess of natural deposits based on differences in bioaccumulation among fish populations from these two systems. Cottage Grove Reservoir was examined for environmental evidence of point source mercury pollution. High mercury concentrations were found at various points around the suspected source, the Black Butte Mine area. The highest concentration occurred close to the kiln. The mercury concentration in the sediments of a creek below the mine dump was up to ten times higher than that of the sediments of a creek from a watershed adjacent to the watershed of the mine area. Two sediment cores from the deep area were collected to assess for pollution history profiles. These showed mercury loading in Cottage Grove Reservoir was consistent with the past mercury production in Black Butte Mine. Therefore most of mercury in Cottage Grove Reservoir was believed to be of Black Butte Mine origin. Mercury contents in pore water and food web indicated that continuing mercury transportation from the point source create a management problem in Cottage Grove Reservoir. / Graduation date: 1996

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.