Most Toxic Contaminants from Deepwater Horizion Oil Spill Remain in the Gulf

It turns out that some of the most toxic contaminants from the Deepwater Horizon spill still remain within the Gulf of Mexico. Scientists have found that while bacteria in the Gulf consumed many toxic components of the oil released, they didn't soak up the most toxic contaminants.

The most toxic contaminants of the Deepwater Horizon spill are known as polycyclic aromatic hydrocarbons, or PAHs. PAHs are a group of semi-volatile organic compounds that are present in crude oil and can cause long-term health problems, such as cancer.

"Those PAHs could persist for a long time, particularly if they are buried in the ocean floor where lack of oxygen would slow PAH degradation by microorganisms," said Olivia Mason, one of the researchers, in a news release. "They're going to persist in the environment and have deleterious effects on whatever is living in the sediment."

In order to see what sort of contaminants might still be present, the researchers investigated oil deposits in 64 sediment samples in different areas around the oil wellhead in the Gulf of Mexico. Then, the researchers sequences microbial DNA in 14 of these samples to understand the functional capacity of the microorganisms to degrade oil. Of the 14 samples, seven were contaminated with PAHs to the point where they exceeded EPA water quality benchmarks.

The researchers found that a species of bacteria, Colwellia, can consume gaseous hydrocarbons and perhaps benzene, toluene, ethylbenzene and xylene compounds. Yet this bacteria did not consume the most toxic parts of the oil spill in the water column plume or in the oil that settled on the seafloor.

The findings reveal that we may have to deal with these contaminants for years to come. In addition, it highlights the importance of finding ways to effectively deal with these toxins in the environment.

The findings are published in the journal Frontiers in Microbiology.