No abstract

Organochlorine compounds (OCs) such as DDTs (DDT and its metabolites), PCBs (polychlorinated biphenyls), CHLs (chlordane compounds), and HCHs (hexachlorocyclohexanes) were determined in the blubber of Baikal seal (Phoca sibirica) and their fish diet collected from Lake Baikal in 1992. Residue levels of DDTs and PCBs were in the ranges of 4.9-160 pg/g and 3.5-64pglg on a lipid weight basis, respectively. The concentrations of CHLs and HCHs were approximately 1 or 3 orders of magnitude lower than those of DDTs and PCBs. Comparison of OC residue levels with those reported for other pinnipeds suggests that Baikal seal is highly contaminated species vulnerable to OC toxicity. A positive age-dependent accumulation of DDTs, PCBs, and CHLs was found in males, while a steady state observed in females suggested the transfer of these chemicals from mother to pup through gestation and lactation. On the basis of contaminant burdens in adult seals, it was estimated that an adult female Baikal seal transfers about 20% of its total DDTs and 14% of its total PCBs to the pup during a reproductive process. Based on the data from isomer-specific analysis of PCBs, it can be suggested that Baikal seals have a higher or comparable capacity to metabolize toxic contaminants than marine mammals, but it is apparently lower than terrestrial mammals, which seems to be a causative factor for the higher accumulation of OC residues in this species. lntroduetion Lake Baikal, located in eastern Siberia, Russia, (Figure l), is known for many superlatives: the deepest (1632m1, the largest volume of freshwater (one-fif&h of the world's deposits of liquid freshwater), and geologically the most ancient (over 25 million years). Among many unique and endemic animals and plants in this lake, one of the most concern is the Baikal seal, which is a species inhabiting freshwater. They occupy the highest niche in the food chain of Lake Baikal.In 1987 and 1988, an acute disease struck the Baikal seal, and several thousands of animals died (1). Although the direct cause for this outbreak was a morbillivirus infection (1, 21, the potential factors behind the sudden infection by this virus have not been ascertained. Such mass mortalities in marine mammals have frequently been found worldwide in the latter half of this century (3). Since these disasters have mostly occurred nearby industrialized coastal areas (41, it is suspected that some stressors such as chronic exposures to toxic man-made chemicals might have played a role in triggering serious symptoms in epizootics by immunosuppression in mammals (4-6).Previous investigations reported the presence of high levels of OC residues in marine mammals (7,8), and some of them were discussed in association with the occurrence of several abnormalities (8-111, Adverse effects on reproductive and immunological functions were also noted in captive seals fed with high levels of persistent OCs (12,13). Nevertheless, in contrast to that in marine species, very few investigations are available for freshwater species inhabiti...

No abstract

Concentrations of perfluorochemicals (PFCs) including perfluoroalkylsulfonates (PFSAs) and perfluoroalkylcarboxylates (PFCAs) were determined in liver and serum of Baikal seals (Pusa sibirica) collected from Lake Baikal, Russia in 2005. Among the 10 PFC compounds measured, perfluorononanoic acid (PFNA, 3.3-72 ng/g wet wt) concentrations were the highest in liver, followed by perfluorooctanesulfonate (PFOS, 2.6-38 ng/ g). The accumulation profile of long-chain (C7-C12) PFCAs in particular, the predominance of PFNA, indicated that 8:2 fluorotelomer alcohol or commercially manufactured PFNA is a major local source of PFCs in Lake Baikal. No gender-related differences in the concentrations of individual PFCs or total PFCs were found. Tissues from pups and juveniles contained relatively higher concentrations of PFCs than tissues from subadults and adults, suggesting that maternal transfer of PFCs is of critical importance. Comparison of concentrations of PFCs in livers and sera collected from the same individuals of Baikal seals revealed that residue levels of PFOS, PFNA, perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) were significantly higher in liver than in serum. The concentration ratios of PFNA and PFDA between liver and serum were calculated to be 14 and 15, respectively, whereas the ratio of PFOS was 2.4. This suggests preferential retention of both PFNA and PFDA in liver. Concentrations of PFOS, PFNA, and PFDA in liver were significantly correlated with those in serum, whereas concentrations of PFUnDA were not correlated in between the two tissues, suggesting differences in pharmacokinetics among these PFCs. Temporal comparisons of hepatic PFC concentrations in seals collected between 1992 and 2005 showed that the concentrations of PFOS (p ) 0.0006), PFNA (p ) 0.061) and PFDA (p ) 0.017) were higher in animals collected in recent years, indicating ongoing sources of PFC contamination in Lake Baikal.