PERSISTENT ORGANOCHLORINE RESIDUES AND THEIR ACCUMULATION KINETICS INBAIKAL SEAL (PHOCA-SIBIRICA) FROM LAKE BAIKAL, RUSSIA

Organochlorine compounds (OCs) such as DDTs (DDT and its metabolites), PCBs (polychlorinated biphenyls), CHLs (chlordane compounds), and HCH s (hexachlorocyclohexanes) were determined in the blubber of Baikal se al (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 mu g/g and 3.5-64 mu g/g on a lipid weight basis, respectively. The conc entrations of CHLs and HCHs were approximately 1 or 3 orders of magnit ude 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, whi le a steady state observed in females suggested the transfer of these chemicals from mother to pup through gestation and lactation. On the b asis of contaminant burdens in adult seals, it was estimated that an a dult 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 t he data from isomer-specific analysis of PCBs, it can be suggested tha t Baikal seals have a higher or comparable capacity to metabolize toxi c contaminants than marine mammals, but it is apparently lower than te rrestrial mammals, which seems to be a causative factor for the higher accumulation of OC residues in this species.