So where did the oil go? ... Perhaps the most important cause of the oil’s disappearance, some researchers suspect, is that the oil has been devoured by microbes. The lesson from past spills is that the lion’s share of the cleanup work is done by nature in the form of oil-eating bacteria and fungi. The microbes break down the hydrocarbons in oil to use as fuel to grow and reproduce. A bit of oil in the water is like a feeding frenzy, causing microbial populations to grow exponentially.
Typically, there are enough microbes in the ocean to consume half of any oil spilled in a month or two, says [Cornell University ecologist Richard Howarth]. Such microbes have been found in every ocean of the world sampled, from the Arctic to Antarctica. But there are reasons to think that the process may occur more quickly in the Gulf than in other oceans.
Microbes grow faster in the warmer water of the Gulf than they do in, say, the cool waters off Alaska, where the Exxon Valdez spill occurred. Moreover, the Gulf is hardly pristine. Even before humans started drilling for oil in the Gulf — and spilling lots of it — oil naturally seeped into the water. As a result, the Gulf evolved a rich collection of petroleum-loving microbes, ready to pounce on any new spill. The microbes are clever and tough, observes Samantha Joye, microbial geochemist at the University of Georgia. Joye has shown that oxygen levels in parts of the Gulf contaminated with oil have dropped. Since microbes need oxygen to eat the petroleum, that’s evidence that the microbes are hard at work.
The controversial dispersant used to break up the oil as it gushed from the deep-sea well may have helped the microbes do their work. Microbes can more easily consume small drops of oil than big ones. And there is evidence the microbes like to munch on the dispersant as well.
The article also says that a large portion of the oil simply evaporates into the atmosphere.
Edited by Palisade, 29 July 2010 - 02:53 PM.