The petroleum that had leaked from the well before it was sealed formed a slick extending over more than 57,500 square miles (149,000 square km) of the Gulf of Mexico. To clean oil from the open water, 1.8 million gallons of dispersants—substances that emulsified the oil, thus allowing for easier metabolism by bacteria—were pumped directly into the leak and applied aerially to the slick. Booms to corral portions of the slick were deployed, and the contained oil was then siphoned off or burned. As oil began to contaminate Louisiana beaches in May, it was manually removed; more difficult to clean were the state’s marshes and estuaries, where the topography was knit together by delicate plant life. By June, oil and tar balls had made landfall on the beaches of Mississippi, Alabama, and Florida. In all, an estimated 1,100 miles (1,770 km) of shoreline were polluted.

The various cleanup efforts were coordinated by the National Response Team, a group of government agencies headed by the U.S. Coast Guard and the Environmental Protection Agency (EPA). BP, Transocean, and several other companies were held liable for the billions of dollars in costs accrued. Coast Guard cleanup patrols ultimately drew to a close in Alabama, Florida, and Mississippi in June 2013 and in Louisiana in April 2014.

Aftermath and impact

Economic prospects in the Gulf Coast states were dire, as the spill affected many of the industries upon which residents depended. More than a third of federal waters in the gulf were closed to fishing at the peak of the spill, due to fears of contamination. A moratorium on offshore drilling, enacted by U.S. Pres. Barack Obama’s administration despite a district court reversal, left an estimated 8,000–12,000 temporarily unemployed. Few travelers were willing to face the prospect of petroleum-sullied beaches, leaving those dependent on tourism struggling to supplement their incomes. Following demands by Obama, BP created a $20 billion compensation fund for those affected by the spill. A year later nearly a third of the fund had been paid out, though lack of oversight allowed government entities to submit wildly inflated claims, some unrelated to the spill. By 2013 the fund was largely depleted.

Recovery was incremental. As oil dispersed, portions of the gulf began reopening to fishing in July, and by October the majority of the closed areas were judged safe. State governments struggled to draw attention to unsoiled or newly scrubbed beaches with advertising campaigns, often drawing on funds from BP. Oil continued to wash ashore in many areas, and much of it could not be removed, either because of logistical reasons—mats of submerged oil and organic matter collected in tidal zones that were difficult to reach—or because cleaning it up would inflict greater harm on the ecosystem. The drilling moratorium, initially set to expire in November 2010, was lifted in mid-October, though new drilling permits were not issued until February of the subsequent year following mounting government and industry pressure to increase domestic oil production.

The emergence of BP chief executive Tony Hayward as the public face of the oil giant further inflamed public sentiment against the embattled company. The Englishman—who at one point remarked, “I’d like my life back”—was derided for his alternately flippant and obfuscating responses in media interviews and while testifying before the U.S. Congress. He was replaced in October. By the next year, the company had lost almost a quarter of its market value and had hemorrhaged over $40 billion in costs associated with cleanup and recovery.

The National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, formed by Obama in May 2010, faulted the Obama administration’s response to the spill in a report issued in October. The commission’s final report, issued in January 2011, attributed the spill to a lack of regulatory oversight by the government and negligence and time-saving measures on the part of BP and its partners.

A report released in September by the Joint Investigation Team of the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) and the U.S. Coast Guard emphasized BP’s ultimate responsibility for the disaster. (BOEMRE had supplanted the Minerals Management Agency, which had regulated drilling before the spill, in June 2010.) The report noted that, although the defective concrete cap had been installed by Halliburton, decisions about the installation process made by BP had been the cause of the failure. The investigation further found that BP and Transocean employees aboard the rig had—while engaged in testing procedures—ignored early indications of a problem and thus missed opportunities to prevent a full-scale blowout. Though representatives of BP conceded that the company was responsible for some of the factors contributing to the spill, they stressed that their partner companies were also to blame. Halliburton and Transocean similarly pointed to failures on the part of the other parties involved.

In 2020, 10 years after the disaster, the former members of the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling noted that the U.S. Congress had failed to act on most of the recommendations in the final report. However, they did note that the oil industry had improved well containment capability. In addition, a study published in the journal Nature in 2020 found that fish in the Gulf of Mexico continued to show evidence of contamination by polycyclic aromatic hydrocarbons (PAHs).

In 2026, a study using acoustic sensors and direct sampling revealed that animal abundance in deep-water, open-ocean habitats in the Gulf of Mexico fell by 60–85 percent between 2011 and 2015, and abundance remained more than 60 percent below pre-spill levels by 2023. When natural factors such as cycles of water temperatures and oxygen levels that could have affected animal mortality were accounted for, the researchers noticed that evidence of this substantial decline began less than one year after the Deepwater Horizon disaster. The timing and extent of this decline suggested that a large-scale pollution event was directly responsible for the drop in animal abundance.