As It Happens

Deepwater Horizon site still mostly bereft of life — except for parasite-covered crabs

Nearly a decade after an explosion on the Deepwater Horizon drilling rig spilled hundreds of millions of litres of oil into the Gulf of Mexico, the area's deep sea remains largely lifeless — except for shrimp and parasite-laden crabs.

The Gulf of Mexico oil rig wreckage 'should have had things growing on it,' says Craig McClain

A crab with a blackened shell is pictured at the site of the Deepwater Horizon oil spill in the Gulf of Mexico. ( Louisiana Universities Marine Consortium)

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Nearly a decade after an explosion on the Deepwater Horizon drilling rig spilled hundreds of millions of litres of oil into the Gulf of Mexico, the area's deep sea remains largely lifeless — except for shrimp and parasite-laden crabs.

"Most of the rich biodiversity and the amazing life that we've seen in the deep sea was just absent at the Deepwater Horizon site," Craig McClain, executive director of the Louisiana Universities Marine Consortium, told As It Happens host Carol Off.

"Hard substrates like all the wreckage of the rig itself should have had things growing on it, like sea anemones and sponges and corals that would be typical of other spots of the deep sea — and we saw none of that."

The April 20, 2010, BP explosion resulted in the largest accidental release of oil into marine waters in history. Estimates of the size of the spill vary, but a U.S. government panel puts it at 650 million litres over 87 days.

The Deepwater Horizon oil rig burns in the Gulf of Mexico following an April 2010 explosion that killed 11 workers and caused the worst offshore oil spill in the nation's history. (Gerald Herbert/The Associated Press)

McClain and his team used camera-mounted remote-operated vehicles to survey the sea floor beneath the rig in 2017 to see how marine life was faring.

Their findings were published on Aug. 28 in the journal Royal Society Open Science.

Deformed and limbless crabs 

While they didn't see the rich biodiversity that's typical of the deep sea, they did find far more crustaceans than they expected — mostly shrimp and red deep sea crabs.

The crabs, MClain said, were in particularly rough shape, with blackened shells covered in parasites. 

"They were sometimes missing legs and claws," he said. "There's a lot of shell deformities that we saw."

Crabs are unexpectedly plentiful at the site of the Deepwater Horizon oil spill, but they're not in good shape. (Deepwater Horizon oil spill)

The team was unable to collect any samples, so they can only theorize about what happened to the critters. 

McClain said it's likely that the decomposing oil is mimicking a sex hormone that's luring the unsuspecting crabs to the site — a phenomenon that's been observed in lobsters at other oil spill sites. 

But instead of finding a mate, they're met with the toxic remnants of the oil spill, which covers their shells and prevents them from properly molting to get rid of the parasites that naturally accumulate. 

A dramatic contrast 

The experience was jarring for the scientists, McClain said. 

"The prior week, we had done dives across the Gulf of Mexico and saw, you know, glass sponges and squids and fish and whip corals and giant isopods, one of my favourite deep sea animals," he said.

"It was the equivalent of walking around in a tropical rainforest and the next day walking around on a cement parking lot."

The sea floor at the Deepwater Horizon oil spill site was still largely bereft if life when scientists explored it using remote-operated vehicles in 2017. ( Louisiana Universities Marine Consortium)

It's going to take a lot more observation and research to fully understand the spill's impact on the deep sea, he said, but he's worried that nobody's paying attention.

His team did the 2017 dive on its own time and dime after completing funded research in a nearby part of the Gulf, he said. But they don't have the money or the equipment to go back. 

"I'm concerned that there's not been an increased effort in and continued monitoring of the recovery or the lack of recovery at the site," he said.

"We can't begin to know what restoration of the deep sea looks like until we actually get a handle of how fast it's recovering in the first place."

Written by Sheena Goodyear with files from CBC News. Interview with Craig McClain produced by Sarah Jackson. 


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