Did Pollution Drive Fish's Evolution?

Well, the answer apparently is yes and no.

By the third generation, the fish reared in the aquarium have lost about half of their resistance to certain toxins, he says, so some adaptations did not alter the mummichog's genome.

But other changes, like their susceptibility to fluctuations in the oxygen level in the water, remain constant through the "grandchildren," as Di Giulio puts it. So some genetic changes seem to be taking place.

"There definitely is an evolutionary event that has occurred there," he says.

"What's important to know is, are we shaping the evolution of organisms?" Di Giulio says. "I think we are. But these fish paid a price. They've lost fitness to other natural stressors. I'm really interested in this tradeoff between being able to adapt versus what the cost of that adaptation is."

Polluted for Years to Come

Meanwhile, back at the Elizabeth River, things are getting a little better. A long range effort to clean up the river — identified in a 1983 Environmental Protection Agency report as one of the most highly polluted bodies of water in the entire Chesapeake Bay watershed — has been partially successful.

These days, posh homes line the banks upriver of the "technological gauntlet," as one report put it, near the mouth of the river. Shipbuilding and industrial operations dumped so many tons of creosote, oil and waste products into the river over the years that two Superfund sites have been designated in an effort to clean up the mess.

But it will take years. One report notes that there may be as many as 1,200 to 4,300 underground storage tanks leaking contaminants into the soil near the river, and much of that will make its way into the Elizabeth.

So the mummichog won't have it much easier for a long time to come. But maybe when it's all over, it will have told us much about the long range impact of pollution.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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