Researchers now have a better understanding of the impact of cleanup and of how an ecosystem recovers. Of these latter studies, work on pink salmon has recently produced some surprising results that, if they hold up, could have widespread implications for water-quality standards. As a commercially critical fish, pink salmon received much attention after the spill. For years, biologists have documented the size and health of salmon populations returning to oiled and unoiled sites in the sound and have conducted laboratory experiments to decipher the precise dangers of hydrocarbons. Such studies are proving to be eye-opening.
Oil is composed of thousands of compounds, including polynuclear aromatic hydrocarbons, or PAHs.
PAHs are not regulated in the aggregate nor for their impact on aquatic life. What Heintz and his team did was to expose pink salmon eggs and embryos to different amounts of total PAHs. Now Heintz and his colleagues have determined that PAH levels as low as 1 ppb harm both pink salmon and Pacific herring. In their most recent studies, which appear in this month's Environmental Toxicology and Chemistry, the scientists found that mortality increased for both species of fish exposed to 1 ppb. And they discovered that the effects of very weathered oil were the same as those of fresh oil - which means that the old oil persisting under gravel in some parts of Prince William Sound could still be harmful.