Oil Spills: Examples

Exxon Valdez Oil Spill

In March of 1989, the oil supertanker Exxon Valdez spilled 11 million gallons of crude oil into the Prince William Sound and impacted some 1,300 miles of coastline. It remains the largest oil spill in U.S. history. A combination of detergents and bioremediation were used in the clean-up. The detergents were nutrient rich, being high in phosphorous and nitrogen compounds. In addition, as part of the bioremediation effort, fertilizers were also used to promote microbial growth. After the first year, the treated areas were dramatically cleaner, Hazen says, but after the second year no improvements were observed. Long-term prospects for the treated area are grim.

Deepwater Horizon Oil Spill 

The last (and only) defense against the ongoing Deepwater Horizon oil spill in the Gulf of Mexico is tiny—billions of hydrocarbon-chewing microbes, such as Alcanivorax borkumensis. In fact, the primary motive for using the more than 830,000 gallons of chemical dispersants on the oil slick both above and below the surface of the sea is to break the oil into smaller droplets that bacteria can more easily consume.

"If the oil is in very small droplets, microbial degradation is much quicker," says microbial ecologist Kenneth Lee, director of the Center for Offshore Oil, Gas and Energy Research with Fisheries and Oceans Canada, who has been measuring the oil droplets in the Gulf of Mexico to determine the effectiveness of the dispersant use. "The dispersants can also stimulate microbial growth. Bacteria will chew on the dispersants as well as the oil." Just like your automobile, these marine-dwelling bacteria and fungi use the hydrocarbons as fuel—and emit the greenhouse gas carbon dioxide (CO2) as a result. In essence, the microbes break down the ring structures of the hydrocarbons in seaborne oil using enzymes and oxygen in the seawater. The end result is ancient oil turned into modern-day bacterial biomass—populations can grow exponentially in days. "Down in the Gulf of Mexico there is an indigenous population [of microbes] adapted to oil from so much marine traffic and daily spills. Oil is not new," says Lee, who has also been monitoring the plumes of oil beneath the surface. "There are so many natural seeps around the world that if it wasn't for microbes we would have a lot of oil in the oceans."

Already, measurements of oxygen depletion of as much as 30 percent in the Gulf of Mexico seawater suggest that the microbes are hard at work eating oil. "I take the 30 percent depletion of oxygen in water near the oil as indicating bacterial degradation," Atlas says. Ultimately, it is only microbes that can remove the oil from the ocean. "In the long run, it's biodegradation that removes most of the oil from the environment in these situations," Lee says. Or, as Joye puts it, "They're clever, they're tough, they can basically eat nails…. The microbes have to save us again."

Sources:

http://www.sciencedaily.com/releases/2010/05/100504142110.htm

http://www.scientificamerican.com/article.cfm?id=how-microbes-clean-up-oil-spills

Oil Spills