Bugs ate 2 lakh tonnes of oil spill

Hydrocarbon-eating bugs in the Gulf of Mexico cleared over a period of five months at least 200,000 tonnes of oil and natural gas that had spewed into the water body from a ruptured 2010 deepwater well, say US researchers.

Researchers from the University of Rochester and Texas A&M University analyzed an extensive data set to determine not only how much oil and gas was eaten by bacteria, but also how the characteristics of this feast changed with time.

“A significant amount of the oil and gas that was released was retained within the ocean water more than one-half mile below the sea surface. It appears that the hydrocarbon-eating bacteria did a good job of removing the majority of the material that was retained in these layers,” said co-author John Kessler, an associate professor at the University of Rochester.

The results include the first measurements of how the rate at which the bacteria ate the oil and gas changed as this disaster progressed, information that is fundamental to understanding both this spill and predicting the behaviour of future spills, the journal Environmental Science and Technology reports.

Kessler noted: “Interestingly, the oil and gas consumption rate was correlated with the addition of dispersants at the wellhead. While there is still much to learn about the appropriateness of using dispersants in a natural ecosystem, our results suggest it made the released hydrocarbons more available to the native Gulf of Mexico microorganisms.”

Their measurements show that the consumption of the oil and gas by bacteria in the deep gulf had stopped by September 2010, five months after the Deepwater Horizon explosion.

“It is unclear if this indicates that this great feast was over by this time or if the microorganisms were simply taking a break”, said Kessler. “Our results suggest that some (about 40 per cent) of the released hydrocarbons that once populated these layers still remained in the Gulf post-September 2010, so food was available for the feast to continue at some later time. But the location of those substances and whether they were biochemically transformed is unknown.”

Previous studies of the Deepwater Horizon spill had shown that the oil and gas were trapped in underwater layers, or “plumes”, and that the bacteria had begun consuming the oil and gas.

By using a more extensive data set, the researchers were able to measure just how many tonnes of hydrocarbons released from the spill had been removed in the deep gulf waters. — IANS

source : the hindu..http://www.thehindu.com/sci-tech/science/article3889315.ece