Exposure assessment of marine mammals to man-made contaminants is an essential part of work on the conservation and management of wild populations. Over the last ten years, efforts to assess the biological effects of persistent organic pollutants (POPs) contamination, rather than merely measuring concentrations, have been increased. Mechanisms of action and impacts of these pollutants on marine mammals’ physiological systems have been the subject of numerous studies. Evidence of adverse effects on the immune, reproductive and endocrine systems have all been linked with concentrations of POPs in several pinniped and cetacean populations. Is the Sarasota Bay dolphin community, which lives in a fairly closed environment surrounded by human activity, affected by pollution? Evidence of reduction of immune responses, in association with increasing levels of POPs, has been observed in a small number of individuals from this community leading us to an affirmative answer.

Organic contaminants in mammals can be chemically transformed by biotransformation processes sometimes to more persistent and biologically active chemicals, such as the conversion of p,p’-DDT to p,p’-DDE. Other by-products of biotransformation are more readily eliminated. This project will focus on the assessment of polychlorinated biphenyl (PCB) and brominated diphenyl ether (PBDE) metabolites as well as fully fluorinated compounds. Concentrations will be determined from the analysis of dolphin blood plasma collected in the 2002 and 2003 sampling efforts. PCBs are persistent chemicals of known toxicity that are widely distributed in the global marine environment. There is growing evidence that PBDEs are also equally widely distributed. Hydroxylated PCB and PBDE metabolites have had less scientific attention than their parent molecules but may be as toxic in their actions. There is particular concern about the effects of hydroxy-PCBs and PBDEs on thyroid and estrogenic hormone activity. Fluorinated chemicals are, for their part, of increasing concern because of their global distribution in the environment, their impact on cellular biology and their ongoing industrial use. High concentrations of fluorinated chemicals have already been reported in the blood and liver of stranded bottlenose dolphins from Sarasota. Possible use of biological indicators (biomarkers) and in vitro tests may also indicate mechanisms of action and impacts of such contaminants on the endocrine system of dolphins.

Accumulation of contaminants may vary depending on the gender, age and reproductive status of the animals. Females are usually less contaminated with POPs than males because of the transfer of contaminants to the offspring through gestation and lactation. The long-term monitoring of the Sarasota bottlenose dolphin population gives us the unique opportunity to identify the biological parameters prior to adequate interpretation of toxicological data. Does sex and age of dolphins or reproductive history of females affect the concentration of fluorinated compounds in the same manner as it affects chlorinated ones? Are these contaminants associated with effects on the thyroid or estrogen systems in the dolphins? Such questions about these newly studied pollutants that may soon be answered.