Deepwater Horizon Spill Lives On: Scientists Find Extensive Damage to Coral
The 2010 Deepwater Horizon oil spill, which spewed more than 200 million gallons of crude oil into the Gulf of Mexico over three months, is one of the worst environmental disasters in American history.
Now new research indicates that the spill damaged a far wider swath of the Gulf than was thought, and at greater depths, affecting fish, crabs, and 500-year-old coral.
“This study very clearly shows that multiple coral communities, up to 22 kilometers from the spill site and at depths over 1,800 meters, were impacted by the spill,” said Charles Fisher, a Pennsylvania State University biology professor whose November 2011 research was published this week in the journal Proceedings of the National Academy of Sciences.
Normally, the deep-sea fan coral Fisher studied are covered with living tissue. But the coral colonies he examined were covered with a brown, mucus-like film. Coral usually produce that covering as a protective mechanism when they’re stressed, according to Fisher.
When Fisher’s research team removed the mucus, it revealed patches that were bare, dying, or covered with hydrozoa, a small predatory marine animal.
“When we find a coral colony that has this pathology, that tells us that the entire [marine] community was hit from the toxic chemicals in the oil spill,” said Fisher, who first measured the impacts of the Deepwater Horizon spill on coral colonies in October 2010, six months after the spill.
Because dead coral remain fixed to the ocean floor and leave behind skeletons, they can provide insights about the impact on nearby marine life, Fisher said.
Fish, including sharks, use coral as spawning grounds, and coral provide habitat for fish and golden crabs.
During the 2011 study, Fisher’s team used an underwater vehicle to find five coral colonies located in the direction that the oil plume had traveled.
Two showed effects from the Deepwater Horizon spill. In the first colony, 3.7 miles south of the spill’s origin, about 70 percent of the coral branches in the colony had damaged tissue.
The second colony was 13.7 miles southeast of the oil rig and more than a mile below the surface. Twenty percent of this colony’s branches were affected. It was 50 percent deeper and two times farther from the disaster site than the coral Fisher studied in 2010.
The biologist confirmed that the Deepwater Horizon spill caused the coral’s dysfunction by taking samples from oil embedded in the brown mucus and comparing it with the oil signature associated with Deepwater Horizon.
Fisher said he didn’t know the rate at which the coral branches have been dying or the factors that influence their survival. Some of the less damaged colonies have recovered, he added.
“It’s a cumulative effect,” he said. “What we’ve found is that if a lot of the individual branches were covered with the brown stuff, then the whole colony didn’t do well.”
Does Fisher think that the coral colonies can bounce back?
“The jury is still out,” he said. “Some are getting better; some are getting worse. But they have a low metabolism, and it takes a long time to play out, so it will be a few years until we know the answer.”