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Chemical Contaminants in Gray Whales (Eschrichtius robustus) Stranded in Alaska, Washington, and California, U.S.A.
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1993
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Description:The concentrations of chlorinated hydrocarbons (CHs) such as polychlorinated biphenyls (PCBs), 1,1,1-triehloro-2,2-bis (p-chlorophenyl) ethanes (DDTs), l,l-dichloro-2,2-bis (p- chlorophenyl) ethenes (DDEs), and chlordanes, and essential (e.g., zinc, selenium, copper) and toxic (e.g., mercury, lead) elements were measured in tissues and stomach contents from 22 gray whales (Eschrichtius robustus) stranded between 1988 and 1991. The stranding sites ranged from the relatively pristine areas of Kodiak Island, Alaska, to more urbanized areas in Puget Sound, Washington, and San Francisco Bay, California, with the majority of the sites on the Washington outer coast and in Puget Sound. The wide geographical distribution of the stranded whales allowed 1) an initial assessment of whether concentrations of chemical contaminants in these whales exhibited region-specific differences and 2) whether toxic chemicals that accumulate in sediments may have contributed to the mortality and stranding of gray whales near the more polluted urban areas. The concentrations of CHs in blubber (n = 22) showed no apparent significant differences among stranding sites. The summed concentrations of PCBs and DDEs in blubber ranged from 120 to 10,000 and 9 to 2,100 ppb (ng/g) wet weight, respectively. Additionally, no apparent significant differences were observed in the concentrations of CHs or selected elements in liver (n = 10) between whales stranded in Puget Sound and whales stranded at more pristine sites (Alaska, Washington outer coast and Strait of Juan de Fuca and Strait of Georgia). For example, the summed concentrations of PCBs and DDEs in liver ranged from 79 to 1,600 and 7 to 280 ppb, respectively, and the concentrations of the toxic elements, mercury and lead, ranged from 9 to 120 and 20 to 270 ppb, respectively. Analyses of stomach contents revealed low concentrations of CHs, but high concentrations (mean ± standard error, wet weight) of aluminum (1,700,000 ± 450,000 ppb), iron (320,000 ± 250,000 ppb), manganese (23,000 ± 15,000 ppb), and chromium (3,400 ± 1,300 ppb). Similar to concentrations in tissues, no significant differences were observed in concentrations of elements in stomach contents between whales stranded in Puget Sound and whales stranded at the more pristine sites. The relative proportions of these generally nonanthropogenic elements in stomach contents of stranded whales were similar to the relative proportions in sediments, which is consistent with a geological source of these elements from the ingestion of sediment during feeding. Further, the concentrations of CHs in blubber of four whales repeatedly observed in Puget Sound for a time span of 33 to 67 days before they were found dead, were not significantly different from the concentrations in whales stranded on the Washington outer coast or Strait of Juan de Fuca. Thus, overall, the concentrations of anthropogenic chemicals in stranded gray whales showed little relation to the levels of chemical contaminants in sediment and biota in areas in proximity to the stranding sites. Further, the results showed that the concentrations of potentially toxic chemicals in tissues were relatively low when compared to the concentrations in tissues of marine mammals feeding on higher trophic level species, such as fish. The lack of data from apparently healthy gray whales, however, limits the assessment of whether the levels of anthropogenic contaminants found in tissues may have deleterious effects on the health of gray whales.
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