This study was presented at a NOAA Oceans and Human Health Initiative- sponsored symposium at the annual American Association for the Advancement of Science (AAAS) meeting held in San Diego from Feb. 18-22, 2010.
The symposium featured six new studies by NOAA and several external partners. NOAA’s Oceans and Human Health Initiative seeks to address the challenges that decision-makers face in the areas of public health, ocean-related human health impacts, and natural resource management.
As part of the Coastal Georgia Dolphin Health Assessment conducted late in 2009, a NOAA-led research team gave each dolphin a physical exam that included a small tissue biopsy. Analysis of the tissues revealed that the dolphins have the highest PCB levels ever reported in marine wildlife.
Researchers tracked the movements of the study dolphins for several months via radio transmitters attached to their dorsal fins. They discovered that most of the dolphins did not range very far. The implication for human health is that people and dolphins in the region are eating the same seafood.
Last summer, scientists from NOS and the NOAA Fisheries Service studied two groups of bottlenose dolphins. The first group is in Brunswick, Georgia, near a former industrial site where contaminants had leaked into an intertidal marsh. The second group is found at the Sapelo Island National Estuarine Research Reserve, a virtually pristine-looking protected area about 30 miles up the coast toward Savannah.
The purpose of the study, called NOAA’s Coastal Georgia Dolphin Health Assessment, was to gather data on the dolphins’ overall health and to measure the levels of human-made contaminants, called PCBs (polychlorinated biphenyls), in their tissues.
The Georgia dolphins examined in the study had a secret to tell, indeed. Co-principal investigator Dr. Lori Schwacke and her colleagues discovered that the dolphins' tissues contained the highest concentrations of PCBs ever reported in marine mammals.
"In the Brunswick dolphins, the levels are even higher than those seen in transient killer (or orca) whales from the Pacific Coast, which feed on other marine mammals, and are thus higher in the food chain. These orcas have been reported before as having the highest PCB levels in wildlife," Dr. Schwacke says. "And while PCB levels were significantly lower in the Sapelo Island dolphins, they were still higher than what we usually see in coastal U.S. dolphin populations."
A team of researchers experienced in dolphin catch-and-release methods escorts a subject to a specially equipped research vessel. Little is known about the impacts of contaminants on cetaceans. NOAA’s research on the bottlenose dolphins of coastal Georgia sheds new light on these sensitive sentinels of the sea.
While PCBs have been banned in the U.S. since the 1970s, they are known as "legacy contaminants," which, due to their persistence in the environment and their extensive use in the past, continue to be detected in soil, sediments, and living organisms. PCBs, which are known cancer-causing agents, have also been linked to other health issues.
NOAA scientists' preliminary analyses of the Georgia dolphins’ tissues detected evidence of elevated liver enzymes, suppressed immune function, and altered levels of thyroid hormones—all of which are consistent with the known effects of PCBs on living organisms.
"There are a number of reasons to be concerned about the high levels of PCBs we’re seeing in these dolphins," Schwacke continues. "For one, we learned that except for a few of the males, most of these animals do not range very far, which suggests that the contaminants are moving along the coast through the marine food web."
And people eat the same seafood that dolphins do.
The NOAA research is increasing scientists' knowledge of cetaceans—the group of marine mammals that includes dolphins, porpoises, and whales—which are hard to study in the wild. Until now, little has been known about the impacts that PCBs may be having on the health of cetaceans, which, as the typical apex predators in their habitats, are excellent "sentinel" species that may help scientists determine the overall health of an ecosystem.
As summed up by Dr. Schwacke,"we have to be careful about what we’re doing along our coasts. These contaminants don’t go away. They last for generations. The pollutants that we allow to seep into our waters today are going to be around for decades to come."
The Coastal Georgia Dolphin Health Assessment is a collaboration among NOAA's National Ocean Service, National Centers for Coastal Ocean Science, NOAA Center of Excellence for Oceans and Human Health at Hollings Marine Laboratory, NOAA Fisheries Service Marine Mammal Health and Stranding Response Program, NOAA Southeast Fisheries Science Center, Georgia Department of Natural Resources, National Institute of Standards and Technology, Chicago Zoological Society's Dolphin Research and Conservation Institute, University of Connecticut, Medical University of South Carolina, and Sapelo Island National Estuarine Research Reserve.