Abstract

Steller sea lions (Eumetopias jubatus) have declined precipitously over the last three decades and the western stock is listed as endangered. Toxicity caused by the accumulation of organochlorines (OCs), such as PCBs and DDT, has been demonstrated in other populations and is considered here as one possible factor. Initial surveys have detected significant OC loads. Chemical structure of OCs may account for multiple disturbances at the cellular level leading to disruption in several physiological systems. In order to determine the extent of chemical contamination in Steller sea lions (Eumetopias jubatus ), an analysis of blood serum and blubber samples for both polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT) was completed on 239 Steller sea lions, including juveniles from the Gulf of Alaska, pups from southwest Alaska and the Russian far east and three captive animals. In the central Gulf of Alaska region, 22 blood and blubber samples were collected from juvenile and sub-adult animals. Blood and blubber samples from the same animals in this subset also allows for a medium comparison. PCB levels in blood in these animals ranged from 0.30 to 6.70 ng/g wet weight with a mean of 2.10 ± 0.39 ng/g wet weight and 3162 ± 674 ng/g lipid adjusted. PCB levels in blubber ranged from 230 to 3000 ng/g wet weight with a mean of 1229 ± 188 ng/g wet weight and 3084 ± 582 ng/g lipid adjusted. DDT levels in blood in juveniles and sub-adults ranged from 0.33 to 5.30 ng/g wet weight with a mean of 1.48 ± 0.31 ng/g wet weight and 3404 ± 528 ng/g lipid adjusted. DDT levels in blubber in juveniles and sub-adults ranged from 238 to 3769 ng/g wet weight with a mean of 1300 ± 224 ng/g wet weight and 3216 ± 633 ng/g lipid adjusted. It is interesting to note that lipid adjusted levels are similar between blood and blubber. Of the 214 total pups, 76 pups were from southwest Alaska and the other 138 were from Russia. PCB levels in southwest Alaska pups ranged from 0.21 to 13.00 ng/g wet weight with a mean of 2.12 ± 0.27 ng/g wet weight and 5155 ± 610 ng/g lipid adjusted. In Russia PCBs in pups ranged from 0.33 to 13.00 ng/g wet weight with a mean of 4.24 ± 0.43 ng/g wet weight and 10838 ± 1248 ng/g lipid adjusted. DDT levels in southwest Alaska pups ranged from 0.18 to 11.00 ng/g wet weight with a mean of 1.56 ± 0.23 ng/g wet weight and 3995 ± 575 ng/g lipid adjusted. In Russia DDT in pups ranged from 0.29 to 26.49 ng/g wet weight with a mean of 3.28 ± 0.37 ng/g wet weight and 8396 ± 1067 ng/g lipid adjusted. Average contaminant levels were significantly higher in Russian animals compared to southeast Alaska (for both PCBs and DDT p = 0.001). Three captive animals from the Alaska SeaLife Center provided 69 longitudinal samples with repeated measurements for adult sea lions. PCB levels in captive adults ranged from 1.10 to 17.00 ng/g wet weight with a mean of 4.08 ± 0.27 ng/g wet weight and 10378 ± 835 ng/g lipid adjusted. DDT levels in captive adults ranged from 0.70 to 16.91 ng/g wet weight with a mean of 3.52 ± 0.27 ng/g wet weight and 8844 ± 802 ng/g lipid adjusted. This type of analysis suggests that contaminant exposure and potential effects may be more pronounced in Steller sea lion pups from Russia. Additional analysis will consider the relationship of contaminant level to endocrine disruption of cortisol and thyroid hormone in Steller sea lions.