A study of pink salmon, still ailing a decade after the 1989 Exxon Valdez oil spill, suggests that oil is hundred times more toxic to developing fish than
previously believed and that dangerous oil pollutants linger years longer than had been believed.
National Marine Fisheries Service scientists began the study in 1993 after Alaska Department of Fish and Game biologists were stumped by a mystery: Why were pink salmon spawned in streams oiled by
the disastrous Exxon Valdez spill still suffering years later?
To find the answer, scientists in the NMFS laboratory in Auke Bay, Alaska, simulated the salmon's spawning conditions. They raised salmon in the laboratory in old, weathered oil like that persisting
on many beaches along Alaska's Prince William Sound years after the huge tanker spill.
The result: juvenile fry with gross deformities such as extra fins, retarded development or other problems that create poor prospects for survival through adulthood.
"Think of foetal-alcohol syndrome in humans,'' said Stanley Rice, an NMFS toxicologist and one of the authors of the studies. "In the wild environment, that's kind of what we're having with the pink
salmon fry.'' The results contradict previous assumptions that the light elements of oil, which cause acute effects on marine life but evaporate within days, are the most toxic, he said. "Back in the
'70s we were thinking mostly of the short-term toxicity. We really didn't think there would be that many long-term effects.''
Rice said the studies have caused scientists to rethink water-quality standards. Even Alaska's standards, which are the nation's toughest and restrict hydrocarbon pollution to 15 parts per billion,
may not be strict enough, he said.
The Auke Bay scientists found that weathered oil even at the minute levels of 5 to 20 parts per billion caused salmon to return as adults at rates 40 percent lower than normal. "That's a pretty
significant result at the parts-per-billion level,'' Rice said.
Exxon scientists dispute the findings. The company has long maintained that Prince William Sound was full of hydrocarbons even before the 1989 disaster, the result of natural oil seeps, and marine
life there was accustomed to oil exposure. But the Auke Bay scientists and researchers from the U.S. Geological Survey have concluded that any background, non-spill hydrocarbons in the sound came
from coal, which sinks to the sound's bottom and is locked in a crystalline structure unavailable to marine life.
The important source of oil in Prince William Sound before 1989 was a spill of fuel from Valdez storage tanks that were ruptured and toppled in a powerful earthquake that struck the area in 1964,
according to a study by Keith Kvenvolden of the U.S. Geological Survey. Rice said the scenic area, with only a few thousand residents, will eventually heal from the 1989 disaster. "Unless it has
another Exxon Valdez, Prince William Sound is going to do well from a wildlife perspective,'' he said.
But the outlook is much gloomier for marine life in waterways near major cities like New York, San Francisco and Philadelphia, where a constant flow of spilled oil and other pollution is washed from
streets and parking lots, he said. "It's just the chronic input. These are places where improvement is going to be very poor over the long run.''
Freitag, 30. April 1999