'Invisible' and 'toxic' oil made the Deepwater Horizon spill worse than thought, study says

Doyle Rice | USA TODAY

The worst oil spill in U.S. history was much worse than had been thought, a new study suggests, as the Deepwater Horizon spill of 2010 unleashed "toxic and invisible" oil into the Gulf of Mexico.

"According to our findings, the toxic extent of the spill may have been as much as 30 percent larger than satellite data previously estimated," said study co-author Igal Berenshtein of the University of Miami, in a statement.

The findings revealed that a large part of the spill was invisible to satellites, and yet toxic to marine wildlife.

On April 20, 2010, the Deepwater Horizon oil rig exploded, killing 11 people and releasing 210 million gallons of crude oil into the Gulf of Mexico for a total of 87 days. Oil slicks from the blowout covered an area estimated at 57,000 square miles.

"While the Deepwater Horizon oil spill has been extensively studied, several fundamental questions remained unanswered," Berenshtein and study lead author Claire Paris, also of the University of Miami, told Newsweek. "What was the full extent of the oil spill? Does the satellite footprint account for the entire oil spill extent? And is there a part of the spill that extends beyond the satellite footprint but is still toxic to marine animals?"

Satellites are typically the way researchers track oil spills like the Deepwater Horizon, but this method often underestimates the spill's actual environmental damage. The scientists in this study used three-dimensional computer simulations and previously published on-site measurements to focus on the oil that was invisible to satellites but toxic to organisms.

“We found that there was a substantial fraction of oil invisible to satellites and aerial imaging,” said Berenshtein, in a statement. “The spill was only visible to satellites above a certain oil concentration at the surface, leaving a portion unaccounted for.”

The new findings showed a much wider extent of the spill beyond what could be seen by satellites, as it actually reached the Texas shore, the Florida Keys and even along the east coast of Florida into the Gulf Stream.

It was also toxic enough to kill about half of the marine life in its path.

The new findings will be important for environmental health during future oil spills, according to the study.

“We recommend this method as complementary to satellite estimates,” the authors say. “Currently, satellites provide the most rapid and accurate indication of the locations of the oil slicks. But the oil spill also extends in the water column where currents are (separated) from the upper circulation.”

The new method is "especially important given the global increase in deep-sea drilling efforts and petroleum-related activities," the authors conclude in the study.

The study was published in the peer-reviewed journal Science Advances.