The video of crude oil blasting into the Gulf of Mexico lingered in the public consciousness for days, then weeks, then months.
On April 20, 2010, an explosion at BP's Deepwater Horizon well killed 11 people and began spewing what would become an estimated 210 million gallons of oil into the ocean. For 87 days, Deepwater Horizon's Macondo well went uncapped, resulting in the worst offshore oil spill in U.S. history.
Images of the oil blasting into the Gulf day after day became a staple of news coverage, sparking broad discussion about the use of fossil fuels and the safety of drilling. President Barack Obama launched a commission to investigate the spill and pushed for new regulations to prevent similar disasters. If the spill had a silver lining, it was that it offered hope that the country's relationship with fossil fuels had changed.
But 10 years after the disaster, oceanographers and environmental activists say that any lessons learned have since been tossed aside — and that the same risks remain as before the spill.
"The disaster caused unimaginable economic and environmental devastation, and it absolutely should have been a wake-up call, but unfortunately we're not seeing that those lessons have been learned," said Diane Hoskins, a campaign director at Oceana, an ocean conservation organization with headquarters in Washington.
The Deepwater Horizon disaster unfolded in slow motion. After the well was finally capped, a massive cleanup initiative was launched to recover much of the oil. But according to Oceana, as much as 60 million gallons of oil could still remain in the marine environment.
And with the Trump administration planning to drastically expand offshore drilling in the Pacific, Atlantic and Arctic oceans while rolling back safety regulations, researchers say, the industry risks another catastrophic accident.
"It's just a matter of when," said Antonietta Quigg, a professor of oceanography and marine biology at Texas A&M University at Galveston.
Quigg began studying the effects of the spill as it was happening and continues that work today. Her research focuses on how the leaked oil is broken down by microbes and moves through the food web or gets transported elsewhere in the Gulf, such as sinking to the seafloor.
Quigg and her colleagues are studying oil lingering in the Gulf, but it's impossible to know how much remains — and where it all is.
"That's kind of the billion-dollar question," she said. "We know some has returned to the seafloor and some is trapped in the marshes. Those would be the two main places I would go looking for it."
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On April 14, Oceana released a report detailing some of the consequences of the Deepwater Horizon spill on marine ecosystems. The organization found that as many as 800,000 birds and 170,000 sea turtles were killed by the spilled oil.
Many of these animal populations — some of which, such as Kemp's Ridley sea turtles and Bryde's whales, were already endangered before the spill — are still exhibiting long-term impacts.
"An extraordinary amount of oil went into the Gulf, penetrating Gulf estuaries, coating beaches and coating marshes," said David Muth, director of Gulf restoration for the National Wildlife Federation. "After a disaster like that, you would not expect to see full recovery after 10 years, and indeed we don't."
The Oceana report also highlighted long-term health and economic impacts on Gulf Coast communities and stressed the critical need to prevent a similar accident from occurring. Hoskins said expanding offshore drilling and dismantling safety regulations make for a potentially deadly combination.
"When they drill, they spill," she said. "This is all taking us back to the risky place that we were at in 2010."
One offshore-drilling safety regulation that was put in place after the Deepwater Horizon catastrophe and rolled back by the Trump administration last year required oil companies to test emergency devices known as blowout preventers that are designed to seal off the flow of high-pressure oil and gas from a well. In 2010, it was a failure of this mechanical valve that caused oil to continue spewing from the Deepwater Horizon's Macondo well months after the initial explosion.
Obama appointed Donald Boesch, a professor of marine science at the University of Maryland Center for Environmental Science, in 2010 to serve as a member of the commission to investigate the root cause of BP's Deepwater horizon oil spill. In a 398-page report, the commission found that systemic failings throughout the oil and gas industry contributed to the disaster and that existing systems of government oversight were inadequate.
In response, the Obama administration crafted new regulations for offshore drilling aimed at avoiding the types of mechanical failures that led to the Deepwater Horizon spill.
The commission also issued a series of recommendations to Congress to improve safety and reduce the risk of future spills, but Boesch said lawmakers largely failed to act on the report's guidance.
"All the recommendations we made to Congress for things they could put in statutes related to safety and reorganization — they were never done," he said.
And in recent years, Boesch has watched as Obama-era rules have been dismantled. The Trump administration's revisions did not entirely eliminate the safety regulations, but the rules were relaxed.
"They have to do with the margin of safety," Boesch said. "The revisions give more flexibility to come closer to the edge of what that safety cliff is. They didn't destroy the improvements that were made, but the message it sends out is that safety may be less important."
Yet, one small positive consequence of the accident was that it resulted in the largest environmental damage settlement in U.S. history. The criminal and civil fines resulted in more than $16 billion being dedicated to environmental restoration of the Gulf Coast. Some of the money that has already been allocated has helped scientists better understand biodiversity in the Gulf and how the many creatures that populate the region have been affected by the oil.
"We didn't have a great baseline before, and that was part of the challenge," said Muth of the National Wildlife Federation. "A lot of what has been going on for the past 10 years is not only trying to measure the effects on organisms, but also to get a better sense of how the whole system operates."
Still, experts caution that without sweeping changes, accidents like the Deepwater Horizon spill are just waiting to happen. And given the role that the oil and gas industry plays in accelerating global warming, those changes should ultimately be a shift away from fossil fuels, according to Boesch.
"From a climate change perspective, we know we have to stop using these hydrocarbons," he said. "So the question should not be: How do we lower the risk of a blowout next year? The question should be: How do we decarbonize the world, and what does that off-ramp look like?"
CORRECTION (April 21, 2020, 12:40 a.m. ET): A previous version of this article inaccurately characterized the partisan makeup of Congress after the National Commission on the Deepwater Horizon Oil Spill and Offshore Drilling issued its final report in January 2011. Congress was not controlled by the Republican Party; the House remained under Democratic control until January 2015.