Abstract

The purpose of this study was to evaluate the effects of maternal exposure to organochlorine (OC) contaminants on perinatal mortality among newborn calves of bottlenose dolphins, Tursiops truncatus. Maternal blubber samples were collected by biopsy and levels of 6 isomers of DDT, 11 other OC pesticides and 10 congeners of PCBs were quantified. OC levels were compared for two groups of females, those whose calves survived beyond 6 months and those that were stillborn or died within 8 days of birth. The subjects were 9 adult female Tursiops, five of which were under the care of the U.S. Navy in bay enclosures in San Diego, CA and four that were maintained at Marine World in Vallejo, CA. The subjects ranged in age from 7 to 36 years. The geometric mean concentration of total DDT isomers among dolphins whose calves died was approximately 10 times as high as that among those whose calves survived. Cis- and trans-nonachlor concentrations were the only other pesticides that showed a similar trend. The geometric mean concentration of the sum of all 10 PCBs was nearly twice as high in females whose calves died compared to those whose calves lived. This trend was confirmed in the analysis of individual PCB congeners. The findings of this study, although based on a small number of observations, suggest that body burdens of OC contaminants may have important implications for reproductive success in Tursiops truncatus.