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Bits of Good News From the Gulf

24 August 2010 6:08 pm
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BOSTON—The news out of the Gulf of Mexico doesn't look too bleak, according to preliminary reports here today at the semiannual meeting of the American Chemical Society. The researchers are quick to point out that the human toll of the BP oil spill—both financial and personal—has been devastating. But at least for now, they are seeing only limited environmental damage.

Among the bits of good news is that so far chemical testing on seafood hasn't yet turned up any samples from fish, shrimp, or oysters with dangerous levels of contamination. To date, officials from the National Oceanic and Atmospheric Administration (NOAA), the Food and Drug Administration, and state health agencies in the gulf region have tested some 1034 fish samples from areas closed to fishing due to the spill for compounds such as polycyclic aromatic hydrocarbons (PAHs), a known class of carcinogens. So far, they've managed to detect these and other contaminants from the oil in only a small fraction of the samples—and the levels detected have been between 100 and 1000-fold lower than the levels of known risk, says John Finley, a food chemist at Louisiana State University (LSU) in Baton Rouge who reported some of the results. "It's wonderful news," Finley says. Trevor Penning, a toxicologist at the University of Pennsylvania, agrees that the seafood data so far look good but cautions that the current tests are only a single snapshot. "The seafood may now be safe, but we need to continue to monitor it," Penning says, because it's unclear whether oil remaining in the water or in sediments could eventually contaminate seafood. Because oysters and other bivalves can bioaccumulate PAHs and other compounds, they especially must be closely monitored.

Erik Cordes, a marine ecologist at Temple University in Philadelphia, Pennsylvania, said his first look at some deep sea-floor ecosystems was encouraging.

Over the past decade, Cordes and his colleagues have studied deep marine communities in the gulf, including deep-water corals and unusual tubeworms that live near natural oil seeps. Last month, Cordes and his colleagues visited four of their long-term monitoring sites, each of which is within 32 kilometers of the destroyed oil rig. "Visually, we did not detect any impact. So, so far, so good," Cordes says. "I've never been on a cruise where scientists were so excited by negative results." However, Cordes cautions that these particular sites may not be representative of the entire region. That's because most of the oil either quickly rose to the surface or remains 1000 to 1500 meters deep in underwater plumes, whereas the sites they visited sit in a middle range of 300- to 500-meter-deep waters. Cordes and his colleagues are planning another cruise in October to survey sites they expect are at the same depth and in the path of the current underwater plume.

Edward Overton, a marine chemist at LSU, reported that the oil seems to be degrading and becoming less toxic, largely as expected. He and his colleagues have been performing gas chromatography-mass spectrometry (GC-MS) analyses on dozens of oil samples taken at the surface and at different depths. Overton says he hasn't had a chance to systematically analyze all of his data, but so far he sees evidence that the chemical signature of the oil is changing as it breaks down. GC-MS analyses show that the oil from the Deepwater Horizon site is very complex, containing thousands of different compounds. Early on, oil taken directly from the wellhead was shown to be a very light crude, with over one half of it made up of very light, or small, linear, branched, or circular shaped hydrocarbons. As oil degrades, it normally loses these light components quickly, which are also the most toxic. And that change seems well under way, Overton says.

Still, plenty of bad news remains. Louisiana's wetlands likely will face a long, slow recovery, Overton says. And the latest numbers show more than 1000 turtles, 70 marine mammals, and 4000 birds have died likely due to the spill, says Steve Lehmann, the scientific support coordinator with NOAA's New England district. But those numbers are small compared with the toll from the Exxon Valdez, notes Jeffrey Short, a chemist with Oceana, a marine conservation group. Short, who spent much of his career with NOAA coordinating the agency's efforts in response to the Valdez, notes that that earlier spill claimed an estimated 3100 marine mammals and 100,000 birds.

"Right now things seem to be improving a lot faster than I ever dreamed," Overton says. "I think all of this is good news," he adds. "But we can't say with any certainty that we are out of the woods."

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