Clean-Up Makes Gulf Spill More Toxic
December 1, 2012

2010 Gulf Spill Made Even More Toxic By Clean-Up Effort

April Flowers for — Your Universe Online

In 2010, British Petroleum's Deepwater Horizon offshore oilrig spilled 4.9 billion gallons of oil into the Gulf of Mexico, creating an ecological disaster. A new study from the Georgia Institute of Technology and the Universidad Autonoma de Aguascalientes (UAA) reveals that the two million gallons of dispersant used to clean it up is even worse — 52 times more toxic than the oil alone.

The research team, using oil from the Deepwater Horizon spill and Corexit, the dispersant required by the Environmental Protection Agency (EPA), tested the toxicity of the oil, the dispersant, and mixtures of the two in a laboratory setting. They used five strains of rotifers, a microscopic grazing animal at the base of the Gulf's food chain. Rotifers are very sensitive to toxicants, have a fast response time and are easy to use in tests. This makes them a favored test subject for ecotoxicologists.

The study, published online in the journal Environmental Pollution, found that in addition to causing mortality in adult rotifers, rotifer egg hatching was inhibited by 50 percent in the presence of as little as 2.6 percent of the dispersant mixture. This can have disastrous results on the food chain of the Gulf. Rotifer eggs are laid in the sediment at the bottom of the Gulf where they 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. “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.”

While he was a Fulbright Fellow at Georgia Tech, Martinez performed the research in the laboratory of School of Biology Professor Terry Snell. Snell and Martinez hope that their findings will encourage more scientists to investigate how oil and dispersants impact marine food chains. This would lead to improved management of future oil spills.

“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. “Perhaps we should allow the oil to naturally disperse. It might take longer, but it would have less toxic impact on marine ecosystems.”