RENEE MONTAGNE, host:
Out in the Gulf, there are some encouraging signs. New research shows that bacteria are consuming the underwater oil plume.
As NPR's Christopher Joyce reports, that's a surprise. Last week, another group of scientists said they had not found evidence of oil-eating bacteria near the spill.
CHRISTOPHER JOYCE: Last week, oceanographer Christopher Reddy, from the Woods Hole Oceanographic Institution, said his team had found a big underwater oil plume in May and June. But curiously, the water-borne bacteria that like to eat oil apparently had not found it.
Reddy said microbes are about as predictable as teenagers.
Mr. CHRISTOPHER REDDY (Oceanographer, Woods Hole Oceanographic Institution): Microbes are pretty selective in how they eat oil. Sometimes they kick in; sometimes they don't. Sometimes they do the easiest work; they don't do the hard work.
JOYCE: The hard work is what scientists had been hoping to see - bacteria consuming the more toxic chemicals in the oil plume and rendering them harmless. Reddy said sooner or later, the bugs should show up. Apparently, they have.
Mr. TERRY HAZEN (Microbiologist, Lawrence Berkeley National Laboratory): There's this unique cold-loving bacteria.
JOYCE: That's microbiologist Terry Hazen with the Lawrence Berkeley National Laboratory in California.
Mr. HAZEN: They actually grow better at five degrees than they grow at room temperature.
JOYCE: Hazen and a large team of scientists found these new cold-water bacteria in the oil plume 3,000 feet deep. There are several kinds of microbes, in fact - and they're eating the oil.
Mr. HAZEN: Oil is the only carbon source down there deep, so they immediately take advantage of that. And, of course, they undoubtedly have been adapted to that over millions of years.
JOYCE: That's because oil has been in the water for millions of years, bubbling up from the seabed.
Mr. HAZEN: The Gulf has natural seeps that have been putting the equivalent of an Exxon Valdez spill into the Gulf every year.
JOYCE: So, why hadn't other scientists seen the bacteria? One possibility is that they were looking for low oxygen levels in the water and didn't find them. Low oxygen is the principal sign that lots of bacteria are eating oil.
But Hazen says in this case, ocean currents and the use of dispersants has spread the oil out into a thin veil of tiny droplets, so the bacteria are spread out too. The reason Hazen's team found the bacteria is that they looked for bacterial DNA and enzymes that the microbes express when they eat oil.
That makes sense to microbiologist Benjamin Van Mooy.
Mr. BENJAMIN VAN MOOY (Microbiologist): The thing I'm learning from this project is that there is no shortage of surprises from the microbial point of view.
JOYCE: Van Mooy was on the team from Woods Hole that did not find the oil-eating bacteria.
Mr. VAN MOOY: Every oil spill is unique because the oil has a unique composition and it's also being released into an environment with its own unique chemical and physical factors at play. And then there's also the microbial community.
JOYCE: Scientists working on the Gulf spill say that's why it's hard to predict how the remaining oil in the Gulf will behave. Conditions in the Gulf are different from, say, Alaska, where the Exxon Valdez went aground. The BP oil was released at the sea floor, under great pressure. Dispersants spread it out into cold water, but as it rose, it reached much warmer water.
Hazen says it appears that the combination of bacteria and ocean currents can degrade and disperse the remaining oil in a matter of weeks.
Mr. HAZEN: It does fit with what we've seen. So, in the last three weeks, the plume at depth is completely undetectable.
JOYCE: You're saying the plume is gone?
Mr. HAZEN: Yeah.
JOYCE: But gone doesn't necessarily mean the Gulf is free of BP's pollution. Van Mooy points out that oil has scores of chemical constituents. Bacteria consume the low-hanging fruit first - the harder stuff takes longer to digest. And scientists who track oil say the plume may thin out in one place and then pop up in another. They're continuing to look for signs of that all over the Gulf.
The research, published in the journal Science, was funded by the federal Energy Department, along with support from BP through a university consortium. Scientists at the National Oceanic and Atmospheric Administration say they're following the fate of the microbes and the plume.
Christopher Joyce, NPR News.
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