A comparison of the non-essential elements cadmium, mercury, and lead found in fish and sediment from Alaska and California.

Concentrations of three non-essential elements (cadmium (Cd), mercury (Hg), and lead (Pb)) were determined in sediment and fish from several locations in Alaska (AK) and California (CA) and used to examine differences in bioaccumulation within and between geographic locations. We analyzed tissue (liver, muscle, gill, and stomach contents) from white croaker (Genyonemus lineatus) and English sole (Pleuronectes vetulus) in California and flathead sole (Hippoglossoides elassodon) in Alaska, in addition to several species of invertebrates (mercury only). As found in previous work on arsenic (As) [Meador et al., 2004], Cd in fish liver exhibited a negative correlation with sediment concentrations. No such correlations were found for Hg and Pb when fish liver and sediment were compared; however, these metals did exhibit a positive relationship between liver and organic carbon normalized sediment concentrations, but only for the CA sites. Sediment concentrations of Hg at the AK sites were lower than those for the CA sites; however, AK invertebrates generally bioaccumulated more Hg than CA invertebrates. Conversely, Hg bioaccumulation was higher in CA fish. Even though ratios of total metal/acid volatile sulfides (AVS) in sediment were one to two orders of magnitude higher for the AK sites, bioaccumulation of these elements was much higher in fish from the CA sites. Bioaccumulation factors ([liver]/[sediment]) (BAFs) were highest at relatively clean sites (Bodega Bay and Monterey), indicating that elements were more bioavailable at these sites than from more contaminated locations. The observation of high BAFs for As in fish from Alaska and low BAFs for the California fish, but reversed for Cd, Hg, and Pb in this study, implies that differences in fish species are less important than the unique geochemical features at each site that control bioavailability and bioaccumulation and the potential sources for each element. Additionally, these data were also used to examine the metal depletion hypothesis, which describes the inverse relationship between elements and organic contaminants documented in some monitoring studies. Our results suggest that the enhanced bioavailability of the metals at some uncontaminated sites is the main determinant for the inverse correlation between metal and organic contaminants in tissue.

Bioaccumulation of arsenic in marine fish and invertebrates from Alaska and California.

Past studies determined that concentrations of arsenic in the liver of flathead sole from Alaska were generally higher than those found in fish from other locations sampled along the west coast of the United States (Meador et al. 1994). A study was conducted to examine arsenic concentrations and patterns of bioaccumulation in fish and potential prey species from two geographic locations. Flathead sole were collected from four sites in the Gulf of Alaska and white croaker and English sole were collected from five sites in California. Potential prey species from each site were also examined and found to contain high concentrations of arsenic. In California, the sites with the lowest sediment concentrations of arsenic, total organic carbon, and acid-volatile sulfides (AVS) contained invertebrates with the highest tissue concentrations. Regression analysis determined that arsenic in polychaetes was highly correlated to sediment concentrations of arsenic normalized to AVS but was higher overall for the California samples. Even though invertebrates from several of the California sites exhibited much higher concentrations of arsenic than invertebrates from the Alaska sites, liver and muscle tissue from flathead sole collected in Alaska usually exhibited higher concentrations than fish from the California sites. When concentrations of arsenic in fish liver were plotted against concentrations of arsenic in sediment normalized to AVS levels, a very high correlation was obtained for all sites. This suggests that AVS, or some factor correlated with AVS, may have been responsible for controlling arsenic bioaccumulation in these fish species through dietary uptake and exposure to arsenic in water. Based on the available data, it appears that dietary uptake may be related to fish tissue concentrations, but uptake of aqueous arsenic may be responsible for the higher tissue concentrations in fish from Alaska.

Chemical contaminants in juvenile gray whales (Eschrichtius robustus) from a subsistence harvest in Arctic feeding grounds.

Gray whales are coastal migratory baleen whales that are benthic feeders. Most of their feeding takes place in the northern Pacific Ocean with opportunistic feeding taking place during their migrations and residence on the breeding grounds. The concentrations of organochlorines and trace elements were determined in tissues and stomach contents of juvenile gray whales that were taken on their Arctic feeding grounds in the western Bering Sea during a Russian subsistence harvest. These concentrations were compared to previously published data for contaminants in gray whales that stranded along the west coast of the US during their northbound migration. Feeding in coastal waters during their migrations may present a risk of exposure to toxic chemicals in some regions. The mean concentration (standard error of the mean, SEM) of sigmaPCBs [1400 (130) ng/g, lipid weight] in the blubber of juvenile subsistence whales was significantly lower than the mean level [27,000 (11,000) ng/g, lipid weight] reported previously in juvenile gray whales that stranded in waters off the west coast of the US. Aluminum in stomach contents of the subsistence whales was high compared to other marine mammal species, which is consistent with the ingestion of sediment during feeding. Furthermore, the concentrations of potentially toxic chemicals in tissues were relatively low when compared to the concentrations in tissues of other marine mammals feeding at higher trophic levels. These chemical contaminant data for the subsistence gray whales substantially increase the information available for presumably healthy animals.