Hidden pools of oil left over from the Exxon Valdez spill 14 years ago continued to damage the Alaskan coastal environment for a decade, killing pink salmon eggs and retarding the population growth of sea otters, harlequin ducks and other wildlife, a new study says.
The 14-year study published today in the journal Science points out that the effects of the 11-million gallon spill into Prince William Sound extended well beyond the initial deaths of 250,000 seabirds, 2,800 otters and 300 harbor seals.
The residual oil became particularly toxic and continued to harm the coastal environment for far longer than expected, the study said. These oily pockets are still tucked beneath boulders or buried below gravel and mussel beds and have escaped sunlight, oxygen and waves that normally would break them down, researchers say.
"Because the Exxon Valdez spill happened in a biological wonderland of sea otters and harlequin ducks, there has been a huge amount of research," said Charles H. Peterson, the paper's lead author and a University of North Carolina marine biologist. "Things we have dismissed as sub-lethal effects actually translate into significant decline in wildlife."
For instance, the study compared the recovery of sea otters on the heavily oiled shores of northern Knight Island with another island in the region that was not coated during the catastrophic spill. The population of sea otters that forages around Knight Island remains half of what it was before the spill, while the population at the other island doubled from 1995 to 1998.
Otters suffer chronic exposure to toxic oil residue by eating contaminated clams and by digging around with their paws into contaminated sandy ocean bottoms, according to the study.
Written by seven university and government scientists, the report was attacked as a bunch of "cartoon depictions" by Exxon Mobil Corp. officials before its release.
"What science has learned in Alaska and elsewhere is that while oil spills can have acute short-term effects, the environment has remarkable powers of recovery," said Frank Sprow, Exxon Mobil's vice president of safety, health and the environment.
After the cleanup of the sound, which cost Exxon Mobil $2.2 billion, and environmental studies and conservation programs, which cost the company an additional $1 billion, it's clear that any remaining oil has been safely encapsulated, he said.
