How bay's spill might cripple its sea life
By Chris Bowman
The gooey "bunker oil" that gummed up San Francisco Bay and miles of coastline poses a more serious, long-term threat to marine life than the more common spills of crude oil, University of California, Davis, studies suggest. The research indicates the bunker oil used to power the container ship that struck the Bay Bridge on Nov. 7 could do significantly more damage to the reproductive systems of marine mammals than the lighter crude oil shipped to refineries. "If you compare the two, bunker oil is more toxic," said Jonna Mazet, drawing on results of her laboratory experiments and other research at the university's Veterinary School of Medicine.
Officials in charge of the cleanup say the immediate danger to wildlife has passed. Cleanup crews have finished removing the oil slicks, shifting efforts to the soiled beaches and stained sea walls, the U.S. Coast Guard announced Friday. Wildlife rescuers have collected more than 1,880 oily sea and shore birds, nearly half of them dead. The International Bird Rescue Research Center in Cordelia released 38 Friday at Half Moon Bay – grebes, scaups and a lone common murre – the first avian spill survivors to be cleaned and returned to the wild. As of Saturday, rescuers had yet to find a marine mammal death or injury attributable to the spill. That doesn't necessarily mean sea otters, harbor seals and sea lions are home free. While the water's surface has been largely restored – crews are still working in the difficult-to-clean salt marshes – an unknown portion of the 58,000-gallon spill sank before mechanical skimmers or natural evaporation got to it, scientists said. There, in the water column, the toxic components of bunker oil can be taken up the aquatic food chain as prey pass contaminants to predators. "Because the volume of oil is relatively small, we hope and think (the cross-contamination) won't be a big issue for this spill," Mazet said. "But it's something we have to watch." The monitoring began Friday as state Fish and Game crews finished collecting more than 1,000 specimens of crab, mussels, herring and surf perch to test for contamination. The state is paying analytical laboratories premium rates to get the test results before Dec. 1, Gov. Arnold Schwarzenegger's deadline on deciding whether to lift a fishing ban he imposed Tuesday in the oil spill area. Though officials don't know yet whether the fish are tainted, the Dungeness crab industry supports the suspension out of caution. The type and concentration of oil contaminants found in the species' tissues will allow state health officials to confirm whether fish and crabs caught in the bay are safe for people to eat. The data also will tell wildlife biologists what chemicals they should be tracking in marine life in the coming years. The toxic exposure assessment is important because the petroleum contamination can impair the immune and reproductive systems of mammals and, ultimately, their population growth. Lawyers for the state also are mindful of these long-term effects as they assess the costs of the spill, with an eye toward collecting damages from the wayward ship's owner, Regal Stone Ltd. of Hong Kong. Marine biologists are well-versed in the environmental effects of crude oil, taking many lessons from the Exxon Valdez spill. The tanker ran aground in Alaska in March 1989, releasing 11 million gallons of crude into Prince William Sound and parts of the Gulf of Alaska. The spill killed thousands of fish, birds, seals and sea otters, and the oil continues to damage the ecosystem much longer than experts anticipated. Much less is known about the bunker oil used to power marine vessels. "We don't have anywhere near the data on bunker oil in toxicity and persistence," Mazet said. The relatively few studies examining the bunker oil, however, suggest that it is measurably more harmful to marine mammals than crude oil. Using ranch-reared mink as a surrogate for sea otters, Mazet found that those that were fed rations tainted with trace amounts of "bunker C" oil bore 70 percent fewer kits than those with Alaskan North Slope crude oil in their feed and those on an oil-free diet. Once mature, the kits born to females given the bunker oil diet had "significantly reduced" reproductive success, according to the 2001 study published in the Journal of Wildlife Diseases. An earlier Mazet experiment examining changes in the blood chemistry of mink suggested sea otters feeding on prey tainted with bunker oil endure greater pain and inflammation than otters on the crude oil diet. In another UCD study published earlier this year, Charles Mohr, a disease expert at the veterinary school, found evidence suggesting that bunker oil can inhibit production of hormones that initiate the flight-or-fight response critical to survival. Bunker oil is the dirtiest and cheapest of the petroleum fuels. The typical bunker fuel used by the more than 2,000 ships entering California ports yearly contains 200 times more sulfur than diesel used by trucks, according to the state Air Resources Board. Bunker oil is essentially the dregs of refining diesel, gasoline and other higher-grade fuels. The thick residue contains higher concentrations of toxic substances such as benzene, napthalene and hydrogen sulfide. Cleaning waterfowl coated in bunker oil involves the extra step of bathing them in warm non-toxic oil to remove the tarballs. Unlike other fuels, the contents of bunker oil can vary widely, depending on the source of the crude oil and the refining method. Coast Guard officials said Friday they do not yet know the exact content of the bunker oil that spilled. They are awaiting results of laboratory tests. ABOUT THE WRITER:
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