ANCHORAGE - Toxic disasters such as the 1989 Exxon Valdez oil spill in Alaska have a far greater and longer-lasting effect on the environment than isolated studies might suggest, according to a review of hundreds of research papers.
The review, led by a researcher at the University of North Carolina at Chapel Hill, is detailed in today's issue of the journal Science.
"The point was to put the pieces of the puzzle together, which gave us an overall message you might not see viewing the pieces separately," said Charles H. Peterson, a marine sciences professor at the university.
The findings, researchers said, show that the consequences of the spill extend beyond the short-term mass wildlife casualties. An estimated 250,000 seabirds and thousands of marine mammals died after 11 million gallons of crude oil spilled into Prince William Sound, contaminating more than 1,200 miles of shoreline.
In the long term, declines have been observed in various marine populations, including stunted growth and indirect mortality increases in pink salmon populations.
Sea otters and ducks also showed high mortality rates years later, partly because they ate contaminated invertebrates. The animals also were exposed to oil when they dug up their prey in tainted soil, said Jim Bodkin, a federal wildlife biologist and one of five Alaska-based researchers who contributed to the review.
Tests showed the animals had elevated levels of enzymes used to metabolize petroleum hydrocarbons, Bodkin said.
"It's taken a long time to accumulate all the information that shows that some populations affected by the spill are not recovering as quickly as expected and are still being exposed to oil," Bodkin said.
Researchers said some shoreline habitats, such as contaminated mussel beds, could take up to 30 years to recover.
The Science article acknowledges that disagreement over the effects of the spill exists between Exxon- and government-funded scientists and notes that unknowns persist.
"Nevertheless, these uncertainties do little to diminish the general conclusions: oil persisted beyond a decade in surprising amounts and in toxic forms," the authors wrote.
What happened in Prince William Sound illustrates the critical need for better environmental protections to guard against chronic exposure of pollutants, the scientists said. In a developed country like the United States, petroleum winds up in the environment in far greater quantities than the Exxon Valdez spill each year - carried through such innocuous channels as storm drains, researchers said.
It's a more subtle form of pollution, but ultimately destructive, said Stanley "Jeep" Rice, a scientist with the National Marine Fisheries Service and one of the authors of the article.
"The good news is that it happens over time and over a good-sized area," Rice said. "But when it's continuous, on a daily low level, it does burden the environment."
Six researchers worked on the review, which took about two years. Peterson said only a fraction of the information compiled is outlined in the article, which concludes with a link to supporting online material.