Early results are in from the first-ever global survey of toxic contaminants in marine mammals--and they're not pretty. Sperm whales across the Pacific, even in mid-ocean areas thought to be pristine, are accumulating humanmade chemicals called persistent organic pollutants (POPs). DDT was the most common pollutant, followed by polychlorinated biphenyls (PCBs).
The data were collected by the research vessel Odyssey during a 5-year investigation of pollution across the world's marine food webs (Science, 11 June 2004, p. 1584). The 12-person crew surveyed sperm whales, which range the globe and eat fish and giant squid. These massive mammals accumulate POPs in their tissues, making them likely indicators of the health of the world's oceans.
The ship's crew used a crossbow to shoot nearby sperm whales with an arrow whose tip removes a small core of skin and blubber without harming the whale. Samples from 424 whales were then analyzed by toxicologist Celine Godard of the University of Southern Maine in Portland. Her preliminary findings showed that whales found in the Sea of Cortez, between the west coast of the Mexican mainland and Baja California, had nearly twice the levels of CYP1A1, an enzyme that detoxifies pollutants, as whales in an area of the mid-Pacific thousands of kilometers from land. The health effects of such exposures are not known.
A test by ecotoxicologist David Evers and colleagues at the Biodiversity Research Institute in Gorham, Maine, showed that mercury levels were higher in skin samples from sperm whales near the Galapagos and in the Sea of Cortez compared with whales elsewhere in the Pacific. Measurements of mercury levels in sperm whales in different regions may provide a much-needed global yardstick to compare the extent of mercury pollution in different regions, Evers says.
"It doesn't matter where you are, these animals are polluted," says biologist Roger Payne, president and chief scientist of the Ocean Alliance, a Lincoln, Massachusetts-based conservation group that funded the work. Results from the survey were announced today after Odyssey docked in Boston Harbor.
Peter Ross of the Canadian Department of Fisheries and Oceans predicts that the findings, once published, will "build a case that these chemicals move around the planet with relative impunity." Payne's team is planning to circumnavigate the globe in 2006 and 2007 to test for pollutants in people who live near especially contaminated areas.