Oily: How a San Francisco Oil Spill Took Its Toll on Fish

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Kurt Rogers / San Francisco Chronicle / Corbis

On Nov. 9, 2007, oil floats on the water inside the Berkeley marina after the cargo ship Cosco Busan hit pilings surrounding a tower support of the San Francisco-Oakland Bay Bridge, spilling its fuel into the bay waters.

How quickly have Americans forgotten about the 2010 Gulf of Mexico oil spill? Fast enough that that last week BP launched an advertising blitz aimed at giving a “progress report” on the company’s cleanup efforts. It’s nothing new for the company—BP started bombarding the country with its widely derided “BP Cares” ads while the oil spill was still ongoing last year—and it hardly means BP is done fighting the government on responsibility for the spill. The Interior Department has slapped BP with regulatory violation notices that will lead to fines related to the spill—fines BP says it will appeal. Still, I doubt BP would greenlight another set of ads unless it felt public attention had so waned on the spill that it wanted to get some credit by reminding Americans that it was still out there doing good work.

But that doesn’t mean the impacts of an oil spill end when Anderson Cooper goes home. A new study published in the Proceedings of the National Academy of Sciences looks at the aftermath of a 2007 oil spill in San Francisco Bay, and finds the accidents has had lingering effects on local fish—effects that continued well after the spill was cleaned up.

On a foggy morning on November 7, 2007, the container ship Cosco Busan collided with the San Francisco-Oakland Bay Bridge, spilling some 54,000 gallons of bunker oil into the bay. That’s more than 3,000 times smaller than the Gulf of Mexico spill, but the fact that the accident occurred in crowded coastal waters meant that the spill was more concentrated. The Deepwater Horizon, by contrast, was more than 40 miles away from shore, and much of the oil dispersed or weathered before reaching land. A concentrated spill—like the 1989 Exxon Valdez accident—can be far more damaging for wildlife.

That’s what researchers from the National Oceanic and Atmospheric Administration (NOAA) and several universities found. Looking at the Pacific herring—an important commercial fish—the team found that bunker oil had accumulated in naturally spawned herring embryos. The oil then interacted with sunlight at low tides, when the light could penetrate the shallow water, to kill the embryos in large numbers.

It’s not new that oil can have toxic effects on unborn fish—the Valdez spill indicated that sort of delayed impact—but the PNAS study shows that even relatively small spills can have long-lasting biological effects, as study co-author Gary Cherr of the University of California-Davis Bodega Marine Laboratory said:

 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. And we didn’t expect that the ultraviolet light would dramatically increase toxicity in the actual environment, as we might observe in controlled laboratory experiments.

The Gulf of Mexico spill hasn’t turned out to be the ecological apocalypse that many environmentalists—and, um, magazine covers—predicted. But that doesn’t mean the story is over. As the PNAS paper shows, oil spills can have biological effects that linger for years, so it won’t be possible to gauge the full impact of the Gulf of Mexico oil spill until well after BP has moved on. Shrimpers in the Louisiana area are reporting that this season has been one of the worst in recent memory.

Dean Blanchard, a seafood processor on Grand Isle said his company would normally process more than 1 million pounds of shrimp in November. This year, they only brought in 40,000 pounds.

“It’s terrible. It’s not even close,” Blanchard said. “The only shrimp we’re getting are from somewhere else.”

We may be done with the Gulf of Mexico oil spill, but that doesn’t mean it’s done with us.

Bryan Walsh is a senior writer at TIME. Find him on Twitter at @bryanrwalsh. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.