Emerging organic contaminants in bottlenose dolphins from Sarasota Bay
By Magali Houde, PhD candidate, University of Guelph, Canada

Thousands of man-made chemicals are produced and used to fulfill the needs of every aspect of our society. Perfluorinated chemicals are used in paints, adhesives, and aqueous fire-fighting foams as well as stain repellent for clothes, furniture and carpets. These chemicals have been detected in human blood and wildlife worldwide including remote regions such as the Arctic. Perfluorinated compounds are known to be toxic in laboratory mammals but their effects on marine mammals are still unknown. Capture, sampling and release of dolphins in the Sarasota Bay provided a unique opportunity to study the exposure of dolphins and their prey to these pollutants. A suite of perfluorinated compounds (totaling 11 substances) was measured in plasma of 50 dolphins live-captured and released between 2002 and 2005. Milk samples from 9 females were also analyzed.

Results demonstrated high concentrations of total perfluorinated compounds in plasma of dolphins (mean concentration of 749 ng/g wet weight). Concentrations detected are, in fact, among the highest reported in wildlife to date. Age, gender and reproductive history of dolphins are known in Sarasota Bay due to the long-term biomonitoring of this community. No correlations could be found between gender and contaminants but concentrations seemed to decrease with age in both males and females. Moreover, higher concentrations were detected in calves compared to their mothers. In order to understand such elevated levels in calves, milk samples were analyzed and perfluorinated compounds were detected suggesting lactational transfer from mothers to offspring.

A second objective was to investigate the distribution and the potential route of entry of these chemicals into dolphins by measuring concentrations of perfluorinated compounds in water, sediment, zooplankton and fish composing the dolphin’s diet. Perfluorinated compounds were detected in all samples analyzed from Sarasota Bay. It was observed that concentrations detected in wildlife generally increased with trophic level (Figure 1). These results indicate that perfluorinated compound can accumulate through the food chain reaching elevated concentrations in dolphins.

Results from this study illustrate that commonly used chemicals are accumulating in the marine ecosystem. With continued use, concentrations are likely to increase and possibly threaten the integrity of the marine ecosystem. Biomonitoring of emerging contaminants is an essential aspect for chemical regulatory assessments and for the conservation and management of wild populations such as marine mammals. This study was funded by the NOAA Fisheries, Dolphin Quest, Disney’s Animal Programs, the National Sciences and Engineering Research Council of Canada and les Fonds de la Recherche sur la Nature et les Technologies (Québec).