Dolphins Bear Heavy Loads Of Pollutants

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POLLUTANT INDICATOR Along with their prey, coastal dolphins ingest pesticides, flame retardants, and other persistent organic pollutants.

Dolphins are famous for their intelligence and playfulness, but environmental scientists also see them as sentinels for pollution in the ocean. Many marine mammals, such as dolphins, sit at the apex of food webs, so pollutant levels in their bodies reflect the amount of contaminants carried by their prey. To measure persistent organic pollutants (POPs) in marine environments along the coast of the southeastern U.S., a team of scientists has surveyed the chemicals’ concentrations in dolphin blubber (Environ. Sci. Technol., DOI: 10.1021/es1042244).

Scientists often study dolphins as surrogates for other marine mammals, which can be much harder to find and sample, says lead author John Kucklick of the National Institute of Standards and Technology: "This is an animal you can lay your hands on, as opposed to a sperm whale." Pollutant levels in dolphins also have implications for human health, he says, because dolphins and people often eat the same fish species.

To conduct their survey, Kucklick and his team tested blubber samples from 300 live male bottlenose dolphins (Tursiops truncatus) from populations in 14 locations offshore of the southern U.S. and Bermuda, along the Atlantic and Gulf of Mexico coasts. Using gas chromatography/mass spectrometry, the researchers measured levels of POPs, such as polychlorinated biphenyls, chlordanes, and DDT, in the samples. They conducted all chemical analyses at one laboratory, to ensure their results were comparable.

In general, dolphin populations near urban areas had greater POP levels than did those close to rural regions. The highest concentrations came from animals living near a Superfund site in Brunswick, Ga. POP concentrations in these dolphins were the highest ever recorded in living marine mammals, about twice as high as the previous record (Sci. Total Environ., DOI: 10.1016/S0048-9697(01)00846-4).

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