When a container ship collided with the San Francisco-Oakland Bay Bridge in 2007, spilling 54,000 gallons of oil into the San Francisco Bay, it devastated one of the last urban fisheries for nearly two years, according to a new study by the University of California, Davis, and the National Oceanic and Atmospheric Administration.
"Based on our previous understanding of the effects of oil on embryonic fish, we didn't think there was enough oil from the Cosco Busan spill to cause this much damage," said Gary Cherr, director of the UC Davis Bodega Marine Laboratory and a study co-author.
The study, which will be published this week in the early edition of the journal Proceedings of the National Academy of Sciences, found that components of Cosco Busan bunker oil accumulated in naturally spawned herring embryos, then interacted with sunlight during low tides to kill the embryos.
“We didn't expect that the ultraviolet light would dramatically increase toxicity in the actual environment, as we might observe in controlled laboratory experiments,” said Cherr.
According to the study, embryos from shallower, intertidal zone not only exhibited nonlethal heart defects, they also showed surprisingly high rates of dead tissue and mortality unrelated to heart defects.
In 2008, almost no live larvae hatched from the natural spawn collected from oiled sites.
"Our research represents a change in the paradigm for oil spill research and detecting oil spill effects in an urbanized estuary," said Cherr.