Gulf of Mexico has greater-than-believed ability to self-cleanse oil spills

Terry C. Hazen, Ph.D., said that conclusion has emerged from research following the 2010 Deepwater Horizon disaster, which by some estimates spilled 4.9 million barrels (210 million gallons) of oil into the Gulf of Mexico. His research team used a powerful new approach for identifying microbes in the environment to discover previously unknown bacteria, naturally present in the Gulf water, that consume and break down crude oil.

"The Deepwater Horizon oil provided a new source of nutrients in the deepest waters," explained Hazen, who is with the University of Tennessee in Knoxville. "With more food present in the water, there was a population explosion among those bacteria already adapted to using oil as a food source. It was surprising how fast they consumed the oil. In some locations, it took only one day for them to reduce a gallon of oil to a half gallon. In others, the half-life for a given quantity of spilled oil was 6 days. This data suggests that a great potential for intrinsic bioremediation of oil plumes exists in the deep sea and other environs in the Gulf of Mexico."

Hazen spoke at a symposium, "Environmental Fate of Petroleum Oils and Dispersants in the Marine Environment," that included other reports relating to the Deepwater Horizon spill.

Oil-eating bacteria are natural inhabitants of the Gulf because of the constant supply of food. Scientists know that there are more than 600 different areas where oil oozes from rocks underlying the Gulf of Mexico. These oil seeps, much like underwater springs, release 560,000-1.4 million barrels of oil annually, according to the National Research Council.

Hazen's team used a powerful new approach for identifying previously recognized kinds of oil-eating bacteria that contributed to the natural clean-up of the Deepwater Horizon spill. In the past, scientists identified microbes by putting samples of water into laboratory culture dishes, waiting for microbes to grow and then using a microscope to identify the microbes. The new approach, called "ecogenomics," uses genetic and other analyses of the DNA, proteins and other footprints of bacteria to provide a more detailed picture of microbial life in the water.

"The bottom line from this research may be that the Gulf of Mexico is more resilient and better able to recover from oil spills than anyone thought," Hazen said. "It shows that we may not need the kinds of heroic measures proposed after the Deepwater Horizon spill, like adding nutrients to speed up the growth of bacteria that breakdown oil, or using genetically engineered bacteria. The Gulf has a broad base of natural bacteria, and they respond to the presence of oil by multiplying quite rapidly."