Gulf of Mexico Oil Spill Clean Up Toxic to Marine Life

First Posted: Dec 01, 2012 02:46 AM EST

Mixing dispersants with oil leads to nearly a 52-fold increase in toxicity over the oil alone, according to a study .

One of the largest accidental oil spills in history occurred on April 20, 2010. An explosion occurred aboard the Deepwater Horizon, a drilling rig in the Gulf of Mexico that was connected to a well owned by the oil company BP.

In the weeks following the oil spill, world news was dominated by illustrations of the spill and its growing size as oil continued to leak from an underwater well and pollute the Gulf of Mexico's waters. The spill had a massive affect on the wildlife; it damaged fisheries and trampled the overall economy of the Gulf region.

For over more than 12 weeks in 2010, BP's well discharged nearly 200 million gallons of oil into the Gulf of Mexico and the company used more than 1.8 gallons of dispersants on the oil's surface underwater in an attempt to split the oil into tiny droplets.  

There were studies done that stated dispersants didn't have 'significant' problems for the environment and marine life. But then the dispersants were never used a mile underwater or in such large amounts.

But a recent study has proved the previous findings wrong by stating that the two million gallons of dispersant used to clean up the oil spill, apparently made it 52-times more toxic.

This new finding has been presented by the researchers from the Georgia Institute of Technology and Universidad Autonoma de Aguascalientes (UAA), Mexico.

In toxicity tests in the lab, the mixture's effects increased mortality of rotifers, a microscopic grazing animal at the base of the Gulf's food web. 

Using oil from the Deep Water Horizon spill and Corexit, the dispersant required by the Environmental Protection Agency for clean up, the researchers tested toxicity of oil, dispersant and mixtures on five strains of rotifers. 

Rotifers were used because of their quick response time, ease of use in tests and sensitivity to toxics; the ecotoxicologists have often used rotifers to assess the toxicity of marine water.

In addition to causing mortality in adult rotifers, as little as 2.6 percent of the oil-dispersant mixture inhibited rotifer egg hatching capacity by 50 percent. 

Inhibition of rotifer egg hatching from the sediments is harmful to the environment because these eggs hatch each spring, reproduce in the water column and provide food for baby fish, shrimp and crabs in estuaries.

"Dispersants are preapproved to help clean up oil spills and are widely used during disasters," said UAA's Roberto-Rico Martinez, who led the study. "But we have a poor understanding of their toxicity. Our study indicates the increase in toxicity may have been greatly underestimated following the Macondo well explosion."

"What remains to be determined is whether the benefits of dispersing the oil by using Corexit are outweighed by the substantial increase in toxicity of the mixture," said Snell, chair of the School of Biology. "Perhaps we should allow the oil to naturally disperse. It might take longer, but it would have less toxic impact on marine ecosystems."

The findings are published online by the journal Environmental Pollution and will appear in the February 2013 print edition.

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