Harbor seals in the Gulf of Maine are contaminated with a variety of pollutants, including high levels of PCBs, dioxins, DDT and mercury, according to two new studies by a Maine researcher. "We expected the levels to be much lower than they were," said Susan Shaw, founder and executive director of the Marine Environmental Research Institute in Blue Hill. "I think what it says is the levels have come down, but they’re not as low as you would expect. It tells us that these persistent compounds are still cycling in the food chain to an extent."
The studies, which tested 60 stranded and captured seals, are the most extensive that have been done in the last 25 years. The results, which are preliminary, show some chemicals that were banned three decades ago continue to linger in the environment. Shaw also said the prevalence of mercury was "shocking." "The mercury (readings) in the seals in Penobscot Bay were really, really high," she said. James Gilbert, a professor of wildlife resources at the University of Maine who studies seals, said he saw a presentation of Shaw’s work at a conference last year and that her findings are "something we want to watch and keep track of, definitely." Shaw said her tests of harbor seals from the Gulf of Maine to Cape Cod and Long Island Sound have found levels of PCBs and pesticides similar to those in the North Sea and other polluted areas of Europe. "We’re in the same range as the harbor seals in the Gulf of St. Lawrence, which is considered fairly polluted," Shaw said. Tests showed seal pups were the most contaminated.
Shaw presented her work earlier this month at an international scientific conference in Berlin and has been invited to publish her complete findings in a peer-reviewed scientific journal. Gilbert said that before the Marine Mammal Protection Act was passed in 1972, tissue from harbor seals and harbor porpoises was collected in Maine and analyzed by Canadian scientists. "They had high levels of PCBs and DDT, but it wasn’t as high as the Baltic area," he said. "The question is whether that’s gone down or gone up or stayed about the same."