In the aftermath of the 1989 Exxon Valdez oil spill into Alaska’s Prince William Sound, the impact on oiled seabirds and sea mammals was obvious, but nobody knew how much damage the crude oil would cause to future generations of fish.
It turns out that very low embryonic crude oil exposures experienced by pink salmon and Pacific herring caused lasting cardiac defects in both species.
“Our findings indicate that embryonic exposure to very low, environmentally relevant levels of crude oil causes permanent structural and functional changes to the fish heart,” said scientists with the National Oceanic and Atmospheric Administration’s research facilities in Washington State and Alaska.
“These developmental defects initiated during organogenesis in turn led to reduced cardiorespiratory performance much later in juvenile fish. Hence, embryonic injury following crude oil exposure leads to irreversible impairment.”
A federal fisheries study was released Sept. 6 in Scientific Reports, an online only open access website of the publication Nature. It says the irreversible loss of cardiac fitness and consequent increases in delayed mortality in oil-exposed cohorts of pink salmon and Pacific herring may have been important contributors to the delayed decline of pink salmon and herring stocks in Prince William Sound.
The study, led by John Incardona, supervisory research toxicologist with NOAA Fisheries in Seattle, involved more than a decade a research employing criteria that included exposing salmon and herring embryos to water soluble components of Alaska North Slope crude oil and examining cardiorespiratory function, cardiac anatomy and histology in juveniles after seven to eight months of growth in clean seawater. Researchers also used critical swimming speed as a measure of cardiorespiratory performance in juvenile pink salmon and Pacific herring measuring the swimming speed of juvenile pink salmon and Pacific herring.
They found that in addition to reducing swimming performance in both species, embryonic oil exposure affected the eventual shape of the ventricle and outflow tract in juvenile hearts.
Scientists with the National Oceanic and Atmospheric Administration’s research facilities in Washington state and Alaska began this study in 2002, to continue where previous studies at the Auke Bay, Alaska, lab left off, in an effort boosted in part by funding from the Prince William Sound Regional Citizen’s Advisory Council.
The (Exxon Valdez) spill kind of changed the paradigm of oil toxicity,” Incardona said. Previous studies by the Alaska Department of Fish and Game had found that after the spill and subsequent storms the fry hatched from pink salmon migrating through streams that went across an oiled beach looked abnormal. Yet the oil wasn’t physically in the streams.
“Basically the footprint of injury to herring was much greater than realized back in the 1990s,” he said. For us, (at NOAA) the herring fishermen are NOAA fisheries stakeholders. We’re still working on this. We haven’t forgotten about them. It’s a really important scientific question that we’re trying to answer.”