Dispersant Used in Deepwater Horizon Spill is More Toxic to Corals Than Oil Itself

It turns out that the dispersant that was used to help the 2010 Deepwater Horizon oil spill in the Gulf of Mexico may be more toxic to deep corals than the oil itself. Scientists have discovered the cold-water corals could very well suffer for years to come.

About five million barrels of crude oil escaped from the well dripped by the Deepwater Horizon oil rig in 2010. Afterward, nearly seven million liters of dispersants-chemical emulsifiers used to break down oil-were used to clean it up. Although these dispersants are normally applied to the water's surface, this spill marked the first time they were applied at great depth during an oil spill.

"Applying the dispersants at depth was a grand experiment being conducted in real-time," said Erik Cordes, one of the researchers, in a news release. "It was a desire to immediately do something about the oil coming out of the well, but they really didn't know what was going to happen as a result."

In this latest study, the researchers exposed three cold-water coral species from the Gulf to various concentrations of the dispersant and oil from the Deepwater Horizon well. They found that the lethal concentration was far lower for the dispersant, which meant that it was more toxic than the oil.

"It doesn't take as much dispersant to kill a coral as it does oil," said Cordes.

Currently, the researchers are planning to carry out additional studies to try to replicate the concentrations of oil and dispersant that the corals were exposed to during the oil spill. That said, this is the first step in determining the toxic levels of dispersants and their impact on the environment. This could aid in developing future strategies for applying dispersants during oil spills.

The findings are published in the journal Deep Sea Research II: Topical Studies in Oceanography.

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