Atlantic killifish, or mummichog

Toxic Waters Provide 'a Snapshot of Evolution'

By Cheryl Lyn Dybas
Special to The Washington Post
Monday, January 23, 2006

The waters of New Bedford Harbor, Mass., sparkle on sunny days. But beneath the bay's gleaming surface lies one of the most toxic environments in the nation.

"You'd think nothing, absolutely nothing, would be able to live in New Bedford Harbor," says Jim Kendall, a fisherman and president of New Bedford Seafood Consulting. "But you'd be dead wrong. Something does live there, and in huge numbers."

Killifish, three-inch-long saltwater fish common along the Atlantic coast, thrive in these polluted waters. (The Native American name for killifish, "mummichog," means: They go in great numbers.)

"Sometimes they're so thick in the harbor, you could just about walk across on them," Kendall says. "Killifish are super-fish in the way they've 'learned' to exist here."

While some other marine species, such as quahog clams, have also managed to survive in the harbor, most are at much lower numbers than the abundant killifish.

Scientists have been trying to figure out how thousands of killifish manage to spend their days in such a polluted home.

"That's the big question," said toxicologist Mark E. Hahn of the Woods Hole Oceanographic Institution in Woods Hole, Mass. "It's what can happen when animals are exposed over generations to high levels of contaminants." The result goes one way or the other, he said. "The population dies out or it adapts through genetic changes to extreme pollution levels."

New Bedford Harbor was designated a Superfund site in September 1983 by the Environmental Protection Agency. Its bottom sediments are polluted with PCBs, or polychlorinated biphenyls, dumped there as a byproduct of manufacturing processes that took place from the 1940s through the 1970s.

The PCBs degrade slowly, if at all, and today about 850,000 cubic yards of sediment -- equal to 175 football fields each filled three feet deep -- remain laden with the contaminants. The compounds have been found to cause liver and immune system damage and cancer in people and animals.

More than 25 years after the dumping ended and despite two decades of cleanup, the PCB levels are several times higher than the EPA says is safe. Most of the area was long ago closed to fishing and shellfishing.

Luckily for the killifish, however, "they've evolved a way of adapting," said biologist Diane E. Nacci of EPA's National Health and Environmental Effects Research Laboratory in Narragansett, R.I.

"We're beginning to figure out how they succeeded," added Nacci, "which has led to other questions, like: Is this always a good thing?"

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