Opportunities for using Navy marine mammals to explore associations between organochlorine contaminants and unfavorable effects on reproduction

The Department of Defense (DoD) has a unique marine mammal program maintain ed by the US Navy that includes the largest force of bottlenose dolphins, T ursiops truncatus, worldwide. In recent years, this population of cetaceans that lives in netted open water enclosures in San Diego Bay has been monit ored for levels of organochlorine (OC) contaminants in blubber, blood and m ilk. Data generated from these studies have afforded insight into the fate and possible effects of OC contaminants in marine mammals. We now report pr eliminary findings on the effects of maternal OC exposure on pregnancy outc ome. Blubber OC levels were compared between females whose calves survived beyond 6 months and females whose calves were stillborn or died within 12 d ays of birth. The mean concentration of Sigma DDT was more than 3 times as high among dolphins whose calves died as that among dolphins whose calves s urvived beyond 6 months (P = 0.002). Mean Sigma PCB was more than 2.5 times higher in females whose calves did not survive (P = 0.076). This populatio n is a logical sentinel for the assessment of environmentally mediated dise ase. Biological tissues and fluids can be sampled on a regular basis from t he dolphins for accumulation of tissue residues, facilitated by conditioned husbandry behaviors. These trained behaviors help preclude possible altera tions in health measures resulting from capture stress. Animals' diets can be monitored for contaminant levels. With these data, the expertise and fac ilities available at the Navy laboratory and in collaboration with other ex perts in the field, controlled studies can be designed to monitor and asses s dietary exposure, measurable immune and neurologic responses and assess r eproductive and transgenerational effects of contaminants. Biomarkers can b e developed to relate the health of individual animals relative to contamin ant exposures. Such investigations of natural exposure and response scenari os are a logical adjunct to traditional laboratory toxicity studies. (C) 20 01 Elsevier Science B.V. All rights reserved.