Oil has persisted on some Prince William Sound beaches since 1989,when the Exxon Valdez oil tanker hit a reef March 24,1989,releasing 10.8 million barrels of crude oil and killing hundreds of thousands of animals.
“Every time it happens,it makes people who depend on subsistence in the area very nervous about the safety of their food supply,” said Jeffrey Short,Pacific science director for Oceana,an international ocean protection group. “It's very difficult to overcome that suspicion and that has a big cultural impact – it has just clobbered the community there.”
Sea otter and harlequin duck populations in the areas affected by the spill have not recovered. Because the species have “great similarity in how they feed,” both are exposed to oil and oil contaminants when they dig for food,said Kathrine R. Springman,toxicologist and assistant editor for Marine Environmental Research.
“Sea ducks will forage down in the rocky areas for food and,in doing so,will come into contact with oil and oil hydrocarbons,” she said.
The contamination has also altered population dynamics of harlequin ducks,causing an unusually high number of males compared to females.
Research on affected animal populations is ongoing,and hundreds of peer-reviewed projects in research,monitoring and general restoration have been completed since the 1991 Exxon Valdez settlement,according to the Exxon Valdez Oil Spill Trustee Council.
The council includes public officials,scientists and members of the public. It oversees efforts to restore the sound using $900 million from the Exxon settlement.
The company disagrees with those who say the damage persists.
“Prince William Sound,today,is healthy,robust and thriving. … There has been no long-term impact on the species there,” said Rob Young,a spokesman for the company,now ExxonMobil.
Short,Springman and several other scientists studied contaminants and their potential sources in Prince William Sound.
“I had an inkling that the oil from the Valdez was the largest single source of pollution in the sound,and the study helped to confirm that,” Short said. “It showed that other sources that had been suggested as important really weren't.”
Springman said,”By looking at the chemistry,I can distinguish from boat traffic [oil],Exxon Valdez oil and diesel.”
In 2004,Springman and the team deployed more than 400 “virtual fish” into Prince William Sound. These artificial devices are designed to mimic the fatty tissue of aquatic animals that absorb contaminants.
The semi-permeable membrane devices were halfway embedded in the sand or gravel at 53 beach sites in the intertidal zone of Prince William Sound. Some were known or suspected contamination sites,such as boat harbors,salmon hatcheries,the site of Alaska's 1964 earthquake and the site of the Exxon Valdez oil spill. Other sites were chosen randomly.
After about 28 days,the devices were collected and all collected contaminants were injected into several thousand juvenile rainbow trout from a California hatchery.
Rainbow trout,which Springman likened to “lab rats with scales,” are commonly used for scientific testing.
The contaminants – which were similar to those found in oil,cigarette smoke and other compounds – produced reaction in the trout livers,suggesting animals native to the affected areas of the sound also were being affected.
Springman said all fish injected with contaminants from oil-exposed sites “showed a reaction and a significant one. … It came down to oil.”
Since the accident,Exxon has hired scientists to monitor and report on the effects of the spilled oil on the sound,Young said. “The vast majority of the science basically confirms the positions we now have.”
The scientists have published about 400 peer-reviewed articles,he said.
“The recovery of Prince William Sound conforms very well with the recovery of other oil spills in other parts of the world,” he said.
Springman said consuming fish from the sound isn't harmful to humans because the contaminants are rapidly absorbed and eliminated by the fish bile and liver,not the muscle,which most people eat.
“Oil is a complex mixture of hundreds of compounds,” Springman said. “What happens is that those compounds that are of greatest concern to us in terms of toxicity degrade at different rates.”
The study appeared in Marine Environmental Research,a scientific journal published by Elsevier in 2008.
Short said there is no practical way to clean up Prince William Sound completely,but warnings should be posted on the most contaminated beaches.
More “intrusive” attempts to clean up the oil would be “prohibitively expensive,” he said.
“If they went in to dredge it,guess what you would do? You would re-expose a lot of wildlife to a lot of oil – that is a whole messy thing,” Springman said.