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Bottlenose Dolphin Contaminants Project

The bottlenose dolphin is Georgia’s only year-round resident marine mammal, inhabiting estuaries and near-shore ocean waters. Bottlenose dolphins are ideal sentinels for coastal ecosystem health because they are top predators that are long-lived and tend to accumulate persistent environmental contaminants in their lipid-rich blubber. In 2006, the Nongame Conservation Section began cooperating with NOAA Fisheries, the National Ocean Service and other organizations to measure contaminants in bottlenose dolphins in the Brunswick and Sapelo areas.

Findings indicated that concentrations of polychlorinated biphenyls, or PCBs, in Brunswick dolphins were 10 times higher than bottlenose dolphin - Clay Georgie GDNRany location previously documented. PCBs in the Brunswick and Sapelo dolphins were consistent with a unique PCB mixture, known as Aroclor 1268, that was used at a contaminated industrial site in Brunswick.

Nongame staff helped with a mark-recapture photo-identification study in the Brunswick and Sapelo areas during 2008 and 2009 to estimate dolphin abundance and residence patterns. The study indicated that many of the dolphins in each area are residents, raising questions about dolphin health and contaminant transport in the environment. This project culminated in a two-week dolphin capture and health assessment during summer 2009. Twenty-nine dolphins were captured, given a thorough veterinary examination (samples were collected for contaminant analysis) and tagged with VHF transmitters to track post-capture habitat use and distribution.

Many of the dolphins had high PCBs levels consistent with Aroclor 1268 exposure. Those with high PCB levels had low thyroid hormone levels, several dolphins were smaller than expected for their age and 26 percent were anemic. The Nongame Conservation Section and the National Ocean Service will resume photo-identification monitoring in the Brunswick and Sapelo areas in 2011 with the goal of estimating dolphin calf survival. DNR’s Coastal Resources Division and Wildlife Resources’ Law Enforcement Section have provided extensive logistical support throughout the project.

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