Nature’s janitors mop up mess in Gulf

Being the optimist that I am, this is a story I want to believe. I doesn’t say everything in the Gulf region is hunky dory, nor does it say that tomorrow, life will return to normal. It does give cause for hope and that is not a bad thing.

In the Gulf of Mexico, nature’s janitors are hard at work, mopping up the aftermath of a man-made disaster. On 20 April, 2010, an explosion at the Deepwater Horizon rig unleashed the largest oil spill in US history. Now, a team of American scientists led by Terry Hazen have shown that just a month or so after the incident, a microscopic clean-up crew had already started to digest the mess.

The ocean is home to many groups of bacteria that can break down the chemicals found in crude oil. Some, like Alcanivorax, are oil-eating specialists that are usually found in low numbers, only to bloom when oil spills provide them with a sudden banquet. That’s exactly what has happened in the Gulf of Mexico. Hazen has found that these oil-eaters have swelled in number in the contaminated waters.

Just last week, Richard Camilli from the Woods Hole Oceanographic Institution confirmed that after the explosion, a deep plume of oil the size of Manhattan had persisted for several months in the Gulf of Mexico. Camilli also found that oxygen levels near the plume had remained relatively stable. On the bright side, this was good news for local ocean life for a lack of oxygen would create inhospitable dead zones. But it also suggested that bacteria weren’t breaking down the plume as hoped; if they were, you’d expect to see a fall in oxygen levels.

This evidence was, of course, indirect. Hazen’s team actually looked for oil-eating bacteria themselves rather than just signs of their presence, and their report is more optimistic. Using two ships, they collected samples of water near the broken well between 25 May and 2 June. They discovered the same deep-sea oil plume that Camilli did, around 1,100 metres below the surface, and they found that oxygen levels inside the plume were slightly lower than those outside it. But more importantly, they also found twice as many bacteria within the oily cloud. MORE

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