NEW BEDFORD, Mass., — September 2, 2013 — There's something wrong with the killifish in New Bedford Harbor. They should be dead.
Researchers at the Woods Hole Oceanographic Institution conducting a two-decade-long study of killifish say that the ones thriving in the harbor are contaminated with levels of polychlorinated biphenyls (PCBs) that are so high the fish "should not be able to survive."
"The fact that they are even there at all, that they are surviving in this highly polluted environment is remarkable," said Mark Hahn, a senior scientist at Woods Hole. "The amount of PCBs in their systems is higher than the lethal concentration for that species."
Killifish are prey fish that are usually just a few inches long. They can be found all over the world, but different populations stay in one place and do not migrate. They also reproduce frequently, making them ideal for researching how fish adapt to their environments.
When Hahn and his team began examining New Bedford's killifish in 1995 as part of a Superfund study program, the first thing they looked at was the fishes' enzyme levels.
When healthy killifish from fresh water are exposed to high levels of PCBs, their bodies create an enzyme to help break down the toxins and allow them to survive. When the enzyme is overloaded with the chemical, the fish die because they can no longer process the dose.
The researchers expected that killifish living in Superfund Sites would have high levels of the enzyme to help stave off the toxin.
But New Bedford's killifish do not.
"As we looked into it, we realized that the enzyme level was low because the fish had evolved a tolerance to PCBs," Hahn said.
Hahn said he believes the New Bedford killifish had become resistant to the effects of PCBs decades before his study started. Their resistance may have evolved starting in the 1940s, when industries began dumping PCBs into the Acushnet River.
Read the full story at the New Bedford Standard-Times