Hmmm… The new & improved tomcod can not only withstand exposure to higher levels of PCBs compared to the average, non-evolved fish but it can also sequester extremely dangerous levels of PCBs in its body that historically would have been fatal.
Question of the day: what will happen to the tomcod’s predators and the organisms that eat said predators – including humans – after consuming elevated levels of PCBs along with the tomcod?
Jump right in and enlighten us, hand puppets, the world would love to know – Hudson
By ANNE MINARD of National Geographic News
This story is part of a special National Geographic News series on global water issues.
Bottom-feeding fish in the Hudson River have developed a gene that renders them immune to the toxic effects of PCBs, researchers say.
A genetic variant allows the fish to live in waters notoriously polluted by the now-banned industrial chemicals, and distinguishes the fish—Atlantic tomcod (Microgadus tomcod)—as one of the world’s fastest evolving populations.
“This is very, very rapid evolutionary change,” said Isaac Wirgin, an environmental toxicologist at New York University’s School of Medicine, and the study’s lead investigator. “Normally you think of evolution occurring in thousands to millions of years. You’re talking about all this occurring in 20 to 50 generations maybe.”
PCBs, or polychlorinated biphenyls, were first introduced in 1929 and were used in hundreds of industrial and commercial applications, mostly as electrical insulators. They were banned 50 years later, but they don’t simply degrade. Partly because of PCB contamination, a 200-mile stretch of the Hudson River is the nation’s largest Superfund site.
General Electric released about 1.3 million pounds of PCBs into the Hudson River from 1947 to 1976, and bears most of the responsibility for the cleanup.
Following highly controversial wrangling throughout the past decade, GE conducted a year’s worth of experimental dredging in 2009. The EPA studied the risks from resuspended contaminants and decided cleanup is the best option. Dredging will resume this spring and will last for at least six years.
Cleanup might not be best for tomcod, Wirgin said. That’s because evolutionary theory predicts a genetic mutation like theirs could render them compromised in some other area of their biology, and perhaps not well adapted to life without PCBs.
But it’s likely to be a boon for the Hudson’s predatory fish that are less likely to have an adaptation to PCBs—and are therefore gravely at risk from a diet of tomcod.
The 10-inch Atlantic tomcod has thrived despite the exposure to PCBs, and levels of the chemical in the livers of these fish are among the highest reported in nature. But until now, scientists have never understood how they survived PCB exposures that kill most other fish.
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