Hazen agrees that dilution is a factor. But "there's a lot of biodegradation going on. Clearly we've shown that in the changes in the hydrocarbon ratios," he argues. "The only way that can change is by biodegradation."
Hazen's work on the oil spill sprang from techniques developed as part of BP's $500 million grant to the Energy Biosciences Institute—a research and development joint effort between LBNL, University of California, Berkeley and the University of Illinois–Urbana-Champaign. "This is what enabled us to immediately tell BP we have this whole program, do you want us to come down and help," Hazen says. "They invited us down."
Continued sampling by Hazen and his team—who have been taking samples since late May and will continue to do so in coming weeks, including sediment cores near the well itself—reveals that the plume may now be gone, thanks to the microbes' work and dilution. "For the last three weeks, we haven't been able to find anything in the deep water," he says. "We can't detect anything. It's mostly biodegradation probably."
And scientists agree that one thing is clear: the microbes of the deep Gulf of Mexico were ready to handle an oil spill. Hazen, who has studied previous oil spill sites, notes that natural oil seeps in the region ensure a constant presence of such cold-loving oil-eaters. "There's the equivalent of an Exxon-Valdez worth of oil going into the Gulf every year and that's been going on for millions of years," Hazen says. "These microbes have evolved to take advantage of that and outcompete everybody else."