PLAQUEMINES PARISH, LOUISIANA — South of New Orleans, Plaquemines Parish, a finger of land stretching into the Gulf of Mexico, is dotted with barbecue joints, a naval base, Baptist churches, white egrets, and blue herons, along with roadside displays of shrimp for sale, vacant lots, and crawfish. In a cozy brick house here, filled with the scent of eucalyptus potpourri and home cooking, Captain Kindra Arnesen lives with her husband and dog.

"There's nothing I love more than fishing in the sea, especially in the deep sea. Being high up on the boat, looking out at the endless ocean, it's truly wonderful," Captain Arnesen said in an interview with Mongabay while simmering beans. She has captained small commercial fishing vessels in the Gulf of Mexico for decades. "The only thing better is my grandchildren."

"Before the oil spill, when we went out on the boat, everywhere we went, we could see bonito, blue runners, threadfin, and spinner dolphins leaping as they chased schools of baitfish. There was so much to see everywhere," Arnesen recalled of the time when small schools of fish and spinner dolphins abounded. "After the oil spill, we could go a hundred miles and barely see any baitfish… they were slowly dying."

April 20, 2025, marked the 15th anniversary of the Deepwater Horizon disaster, one of the worst marine ecological disasters in U.S. history. The Deepwater Horizon, an oil drilling rig operated by BP Exploration & Production, exploded and sank in the Macondo Prospect, 66 kilometers (41 miles) off the coast of Louisiana.

The initial explosion killed 11 workers and severely injured 17 others. What followed was the largest offshore oil spill in U.S. history. For nearly three months, oil gushed from the damaged wellhead 1,500 meters (almost 5,000 feet) below the surface, and it wasn't until mid-July 2010 that engineers were able to seal the well.

A total of 4.9 million barrels (approximately 800 million liters) of oil flowed into the ocean. This resulted in the oil slick covering 111,000 square kilometers (43,000 square miles) of the Gulf of Mexico's surface and coating over 2,000 kilometers (1,200 miles) of shoreline with oil and tar balls.

An unprecedented response operation unfolded, involving multiple federal agencies, the governments of the five Gulf Coast states, local authorities, dozens of non-profit organizations and universities, the oil and gas industry, fishing communities, and thousands of volunteers.

BP paid over $20 billion in environmental damage compensation, the largest such settlement in U.S. history, and billions more to individuals and businesses.

Fifteen years later, the Gulf of Mexico tells a complex story of resilience and persistent damage, adaptation and constant threats, bureaucratic failures and scientific breakthroughs. The Deepwater Horizon disaster remains both a testament to nature's ability to recover and a cautionary tale, but many questions about its long-term consequences remain unanswered.

Nature's Resilience and Vulnerability

"Many people don't fully understand the resilience of the Gulf of Mexico," Larry McKinney, former director of the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi, said in an interview with Mongabay. During the oil spill response, McKinney led a team connecting academic researchers with on-the-ground government agencies.

The Gulf of Mexico's resilience stems from its unique structure and rich biodiversity. The Loop Current, flowing in from the Caribbean Sea, circulates and mixes the waters, carrying animals and nutrients throughout the region.

"That whole physical structure is really impressive, and you don't find it in many other places," McKinney said. "Biologically, it's also one of the most biodiverse places in the world. Coral reefs, huge fisheries, whales, dolphins, you name it… everything but ice."

He added, "The problem is we've taken that resilience for granted." While the Gulf has absorbed tremendous shocks and its productivity has recovered, "the biggest issue is that climate change is changing everything so quickly," McKinney warned.

Impact on Wildlife

Whales and Dolphins: Still Suffering

The BP oil spill severely impacted marine life in the Gulf of Mexico, with some animals still struggling while others show signs of recovery. According to the National Wildlife Federation, nearly all 21 species of dolphins and whales that inhabit the Gulf showed signs of injury.

The disaster led to a 22% decline in the population of the critically endangered Rice's whale (Balaenoptera ricei). With only about 50 individuals remaining in the Gulf, another large oil spill could completely wipe them out.

The oil spill also significantly harmed other whale species. Populations of the vulnerable sperm whale (Physeter macrocephalus) decreased by up to 31%, and beaked whales (Ziphiidae) by up to 83%. Current recovery efforts focus on reducing other threats, such as ship collisions and underwater noise.

Cynthia Smith, president and CEO of the National Marine Mammal Foundation, told Mongabay that bottlenose dolphins (Tursiops truncatus) in Barataria Bay, which experienced heavy oiling, are still sick 15 years later.

Smith led the National Oceanic and Atmospheric Administration's (NOAA) dolphin health assessments after the spill. She found "higher death rates, an increase in moderate to severe lung disease, impaired stress responses, high rates of reproductive failure, and overall poor health" compared to dolphins in clean areas.

When Smith's team re-examined them in 2023, the oil-exposed dolphins still had lung problems that were "at least as bad or worse" than before.

Smith said she would never forget one dolphin named Y21, who was pregnant when first examined in 2011, a year after the spill. "She was very sick," Smith said. "You could just see it in her eyes and the way she was breathing. She was kind of listless and very quiet." Y21 lost her calf and two subsequent pregnancies also failed to go to full term, but she survived until 2019.

"She's a really good example of what that whole cohort went through," Smith said. "It wasn't just about survival; it was about health and welfare. She lived a long life, but she was very unhealthy and couldn't reproduce."

Encouragingly, dolphins born after the oil spill appear to be healthier. "I'm optimistic that the next generation of dolphins will lead the population to recovery," Smith said.

Birds: Success Amidst Destruction

One of the most shocking images from the oil spill was of pelicans coated in oil, sticky brown liquid dripping from their feathers, looking like grotesque statues.

P.J. Hahn, former coastal zone director for Plaquemines Parish, was on the front lines of the Deepwater Horizon disaster response. "The oil was just sitting on top of the water, and the fish would jump up and land right on top of that thick oil and just get stuck… they would just bake in the sun. The pelicans would fly in and see the fish and dive. They'd catch the fish, but they'd go right into the oil and come out covered… it was terrible."

The oil spill occurred during the breeding season. "The pelicans would come back to their nests covered in oil and sit on their eggs or chicks, and the eggs or chicks would get covered in oil. And then when they would go off to feed again, the hot sun would just cook the eggs or the chicks," Hahn explained.

Researchers estimate that at least 93 species, approximately one million birds, died as a result of the disaster. Brown pelicans (Pelecanus occidentalis), laughing gulls (Leucophaeus atricilla), northern gannets (Morus bassanus), and royal terns (Thalasseus maximus) were among the hardest hit.

According to the National Wildlife Federation, up to 27,000 brown pelicans died due to the oil spill. The oil also damaged or destroyed critical nesting habitat.

However, the brown pelican is one of the relatively successful recovery stories. Funds from BP's settlement have gone into large-scale habitat restoration projects across the five Gulf Coast states, including rebuilding islands needed by the birds for nesting.

A $18.7 million project funded by the BP settlement expanded Louisiana's Queen Bess Island, creating 15 hectares (37 acres) of habitat for pelicans and other bird species. The results have been impressive. Wildlife officials observed 30,000 birds on Queen Bess Island in 2023, including 6,000 brown pelican nests.

Alicia Renfro, senior manager of coastal policy for the National Wildlife Federation, visited the island in 2025. "It was really amazing to see the baby pelicans, which look like prehistoric birds," she said. "I think if you provide healthy habitat, the populations can recover over time."

Sea Turtles: Long-Term Impacts

The oil spill was a catastrophic disaster for sea turtles in the Gulf of Mexico. Four species of sea turtles were directly exposed to oil in the sea, on the coast, and on beaches: the critically endangered Kemp's ridley (Lepidochelys kempii), the vulnerable loggerhead (Caretta caretta), the endangered green sea turtle (Chelonia mydas), and the critically endangered hawksbill (Eretmochelys imbricata).

The death toll was immense. An estimated 4,900 to 7,600 large juvenile and adult sea turtles, and 56,000 to 166,000 small juvenile sea turtles are believed to have died.

Kemp's ridley sea turtles were hit hardest, with an estimated 27,000 to 65,000 deaths in 2010 alone. Approximately 20% of the entire population of 1- to 2-year-old Kemp's ridley sea turtles at the time died due to the oil spill.

The National Wildlife Federation reports, "Even today, researchers are finding evidence of long-term health impacts in some Kemp’s ridleys, such as abnormal hormone levels that could affect metabolism and other body processes."

Donna Shaver, chief of the Sea Turtle Science and Recovery Division at Padre Island National Seashore National Park, told Mongabay in an interview, "For sea turtles, which are long-lived species that spend most of their time in the ocean, it will take much longer to understand the impacts of the oil spill."

NOAA rescue teams recovered over 300 oiled sea turtles from coastal waters. These turtles were washed, treated, and released into clean waters. Teams also dug up eggs from turtle nests on oil-threatened beaches in Alabama and Florida, moving them to controlled warehouses to hatch safely. Approximately 14,000 hatchlings, mostly loggerheads, were later released into the oil-free Atlantic coast.

Recovery efforts continue in various ways, including reducing light pollution around nesting sites, decreasing deaths from fishing nets, protecting nesting sites in Texas and Mexico, improving rescue networks, and reducing vessel collisions. However, all four species remain threatened with extinction.

The Deep Sea: Hidden Impacts and Slow Recovery

While most people saw oiled turtles, birds, and beaches, some of the worst and longest-lasting damage occurred in deep-sea ecosystems that few people ever see, including vibrant deep-sea coral reefs.

Paul Montagna of the Harte Research Institute, who helped NOAA assess deep-sea damage, told Mongabay in an interview, "When the well blew, the oil came out in small droplets under high pressure, like paint coming out of a spray paint can."

These oil droplets did not float straight to the surface but mixed with "marine snow," a natural phenomenon where small particles like plankton, microbes, and fecal matter constantly fall to the seabed. "The marine snow literally trapped that finely dispersed oil and took it straight to the bottom," Montagna said. "We are pretty confident that 35% of the oil that was spilled went to the bottom through a process we call marine oiled snow sedimentation and flocculent accumulation, or MOSFA."

This oil-soaked marine snow created a toxic layer across vast areas of the seafloor, home to corals, crustaceans, mollusks, polychaetes, and other rare invertebrates. "First, because it’s on top, it’s going to start to suffocate things. Second, because it’s full of polycyclic aromatic hydrocarbons (PAHs), it’s literally going to start to kill things," Montagna said. "Sensitive species declined or disappeared completely."

Montagna found that the area of the seabed with moderate to severe oil damage covered 321 square kilometers (124 square miles). Including areas with possible impacts, that area expanded to 23,388 square kilometers (9,030 square miles), about three-quarters the size of Belgium.

In many areas, the only natural cleaning process is the continuous deposition of new sediment that will gradually cover the contaminated layer. Montagna estimates that it will take 50 years for the deep-sea ecosystems of the northern Gulf of Mexico to fully recover.

Deep-sea corals, which can live for hundreds or even thousands of years, suffered extensive damage. Large colonies of black coral (Leiopathes glaberrima), estimated to be over 2,000 years old, were found damaged or dead in oil spill impact zones.

In a pioneering effort to restore deep-sea corals, NOAA scientists are growing coral fragments in specialized laboratories. Once large enough, these lab-grown corals are carefully transported to the seabed, where U.S. Navy divers and underwater robots place them in damaged areas. This first-of-its-kind deep-sea coral restoration project is still in its early stages, but researchers report signs of success.

Recovery of Aquatic Ecosystems and Remaining Challenges

Immediately after the oil spill, signs of oil exposure appeared in various fish species in the Gulf of Mexico. In 2011, skin lesions were observed in many reef fish, but the incidence of lesions decreased by about half in 2012 as concentrations of underwater oil components declined. Fish exposed to oil suffered various health problems, including heart abnormalities, disorientation, hormone problems, and impaired swimming ability. Changes also occurred in the food chain, with some species shifting to prey found in deeper waters, but most returned to their normal diets by around 2012.

While individual fish experienced significant health impacts, surprisingly, strong evidence of a marked decline in overall fish populations has not yet been found. In particular, off the coast of Alabama, which experienced less oiling than Louisiana, populations of juvenile fish, shrimp, and crabs remained stable after the accident. This is likely because many fish and shrimp have high reproductive rates and wide dispersal abilities, making them relatively resilient to environmental changes. Matt Streich, director of the Sportfish Science and Conservation Center at the Harte Research Institute, explained, "The general reason why many fish and shrimp had minimal impacts at the population level is because they’re resilient, they produce lots of eggs and larvae, and they get dispersed widely by currents."

However, it is difficult for scientists to determine the precise impact of the oil spill on fish populations. Other factors, such as increased fishing pressure coinciding with the accident and the spread of the invasive lionfish (Pterois spp.), have also played a role. Lionfish prey on native fish species and pose a new threat to the Gulf of Mexico ecosystem.

Shattered Fishing Communities and Unending Suffering

Despite some recovery in the aquatic ecosystem, the oil spill severely impacted fishing communities along the Gulf Coast, and the aftermath continues to be felt 15 years later. Kindra Arnesen, a fishing boat captain from Plaquemines Parish, Louisiana, recalled the situation at the time as "horrific and shocking," adding, "I don’t think we even know the full extent of what we lost yet."

Immediately after the accident, fishing was banned in over one-third of U.S. federal waters (229,270 km²) and 95% of Mississippi's and 55% of Louisiana's state waters. Even after the fishing ban was lifted, the situation remained challenging. With the Gulf of Mexico fisheries shut down, imported seafood dominated the market, and many consumers and buyers had already turned elsewhere by the time fishing resumed. Increased regulations and the lingering effects of the oil spill further burdened small-scale fishers.

Wes Tunnell, former director of the Harte Research Institute, said that small fishing businesses were "barely hanging on" after the accident. While large corporations had the capital to withstand the fishing ban, many family-owned small-scale fishing operations went out of business because they could not make a living. To make matters worse, the oil spill occurred just five years after Hurricane Katrina, before the recovery from that disaster was complete. Captain Arnesen experienced the oil spill just months after receiving her Katrina insurance payout. Her boats are now idle, no longer able to sustain her livelihood through fishing.

In addition to economic hardship, many fishers face health problems. Captain Arnesen lamented, "People got sick after the oil spill, but nobody wants to talk about it."

Lingering Health Issues and Trauma for Humans

Justin Solet, a member of the United Houma Nation who became an environmental activist after the oil spill, stated, "It’s been 15 years since the BP oil spill disaster slammed into Louisiana communities." For the United Houma Nation, a tribe of 19,000 people living along the southern coast of Louisiana, hunting, fishing, shrimping, crabbing, and oyster harvesting have been vital parts of their life, livelihood, and culture for centuries. Solet pointed out, "What rarely gets covered in the media is the unknown loss of life due to sickness and suicide, and the many people who abandoned their homes and communities and left."

A 2021 study revealed similar health impacts in both animals and humans exposed to Deepwater Horizon oil, including stress response disorders, cardiotoxicity, immune dysfunction, and blood cell damage. Cynthia Smith of the National Marine Mammal Foundation noted, "Dolphins help us understand the long-term effects of oil exposure on long-lived vertebrates like humans. It is not surprising to our team that some of the health impacts diagnosed in dolphins have also been found in Coast Guard oil spill responders."

Oil cleanup workers experienced a range of physical ailments. A 2018 study published in the American Journal of Medicine reported changes in workers' blood, liver, lung, and heart function years after the accident, along with symptoms such as "respiratory and eye irritation, and chest tightness." Some oil was removed by burning it offshore, and PJ Hahn, Plaquemines Parish’s response coordinator, recalled, "When I arrived on the scene, I witnessed numerous fires with a south wind pushing the contaminated smoke directly into the communities of Venice, Buras, and even Belle Chasse." A 2015 study found lung inflammation and altered immune responses in mice exposed to similar smoke.

Mental health also suffered significantly. Many people experienced depression, anxiety, and post-traumatic stress disorder for years. A 2021 study indicated that some residents found the complex compensation claims process more stressful than the accident itself. Communities reliant on fishing and tourism experienced greater health and economic hardships.

The disaster also exposed a critical issue: the lack of basic health data made it difficult to distinguish between oil spill-related illnesses and other health problems.

Environmental Restoration Efforts and Remaining Tasks

The oil spill triggered numerous health-related lawsuits, but justice remains elusive for most victims. An Associated Press investigation revealed that only one of approximately 4,800 health-related lawsuits filed after the accident reached a settlement, with the rest being dismissed by the courts. BP established a $67 million fund in 2012 for affected workers and coastal residents, but 79% of the roughly 5,000 claimants received less than $1,300 each, a paltry sum compared to their reported medical expenses and ongoing health issues. This pattern of compensation highlights the difficulty of proving a direct causal link between exposure to harmful substances in environmental disasters and specific health conditions.

On the other hand, the disaster led to an unprecedented legal settlement with BP, amounting to billions of dollars, which has been channeled into the restoration of the Gulf of Mexico. Environmental advocates helped push for the RESTORE Act to ensure that funds were directly allocated to affected areas, and then-President Barack Obama signed the bill into law in July 2012. To date, approximately 400 restoration projects have been funded or approved with settlement money, ranging from building boat docks to restoring reefs. Paul Mickle, co-director of the Northern Gulf of Mexico Institute and associate professor at Mississippi State University, assessed, "I think most of the projects are really good."

However, some experts are critical of how the restoration funds are being used. Former Harte Research Institute Director Tunnell noted, "There have been a lot of successes in small, local restorations within bays, estuaries, oyster reefs, or the nearshore. Some of them have been surprisingly encouraging. But it’s too small of a scale. There are good little projects here and there, but nothing measurable at the ecosystem level."

Because the restoration settlement is not tied to the federal government, it is protected from the whims of administrations. Some funds are still accruing interest, and it is expected that funds will be available for at least another decade. However, there are concerns that progress on these projects could stall due to funding and staffing cuts at NOAA and other government agencies under the Trump administration. NOAA provided background information for this article but declined an interview request. 

Of Lingering Questions and Lessons Learned

Fifteen years after the Deepwater Horizon disaster, scientists are still unraveling its full environmental and health impacts. "I think 15 years is too early to say what a lot of the impacts of the spill will still be," said environmental lawyer Misha Collins, who was involved in the passage of the RESTORE Act and is now executive director of Healthy Gulf, a New Orleans-based nonprofit.

In the aftermath of the accident, it became clear that there was little preparation in place to deal with a disaster of this kind. "The Deepwater Horizon oil spill caught everyone flat-footed," said Randy Renfrow of the National Wildlife Federation. "The last major spill was the Exxon Valdez in the 1990s, so everyone was geared up for that kind of event — an oil tanker and a known quantity of oil. Then Deepwater Horizon blew, and oil was gushing a mile below the surface of the Gulf. What do you do with that?"   

Questions still linger about controversial cleanup methods, particularly the use of the dispersant Corexit, which may have caused additional environmental and health damage. "It was toxic in and of itself," Collins pointed out. Burning oil on the surface may also have done more harm than good. "Endangered sea turtles and other marine life were herded into the 500-square-mile 'burn zone' and burned alive during the effort to contain the oil," said Han.   

He also emphasized how crucial local knowledge and management are in disaster response, noting that direction from Washington D.C. hampered initial containment efforts. "There was so much mismanagement and misdirection in all of that… The key is that when a disaster happens, it's always best to involve the people who actually live in the area and know it better than anyone else," Han stressed.

One of the most significant legacies of the Deepwater Horizon disaster is the surge in scientific research and understanding of the Gulf of Mexico ecosystem. Responders are also better equipped to deal with oil spills. NOAA opened a Disaster Response Center in Alabama to coordinate Gulf Coast emergencies. Scientists have developed better tools to track and remove oil, including satellites that can spot the thickest slicks from space, computer models that predict the path of oil, and new ways to measure the impact of oil on marine life. "If there's an oil spill anywhere in the Gulf now, we can run five to 10 models to show where the oil is going to go," said Miceli.   

"The adage that prevention is better than cure is key. We need to be more careful," stressed Montagna of the Harte Research Institute. "Regulations actually work, and they keep us safe." New safety requirements, known as the Well Control Rule, mandate specific equipment to reduce the likelihood of a large blowout. Yet, despite safety measures and improved information and technology, oil spills remain an inevitable part of offshore drilling. Federal records show that nearly 1,000 spills occurred in U.S. waters in 2021-2022 alone, releasing approximately 303,000 liters of oil into the environment from pipelines, transport, and drilling operations. The oil pipelines installed in the Gulf of Mexico alone could circle the Earth. "It's essentially impossible to prevent all oil spills," noted the Natural Resources Defense Council, a New York-based advocacy nonprofit. "For the offshore oil and gas industry, it's simply a cost of doing business."   

"I don't think we learned the lessons that BP should have taught us. We're all focused on deregulation right now," said Collins. "How much further are we going to push until we're proven wrong?"

As the Gulf Coast marks this anniversary, environmental advocates warn of ongoing threats to the region's resilience. Major threats include climate change, continued fossil fuel development, and the Mississippi River outflow. The Mississippi River outflow, from North America’s largest watershed, carries nutrient pollution from agricultural fertilizers, triggering algal blooms and depleting oxygen levels, creating a vast hypoxic "dead zone" that suffocates marine life. "The biggest challenge in the Gulf has very little to do with the oil spill. A lot of it is the water quality issues coming down the Mississippi River," said Miceli.   

"Our system is resilient, but that window of resilience is closing. That window is climate change. If you keep putting pressure on it, at some point it breaks, and when it breaks, it doesn't come back," warned McKinney.

There is Still Hope

About 20 miles south of Arnesen’s house, just beyond the town of Venice — literally "the end of the road," the southernmost point in Louisiana you can drive to — vehicles head toward the crumbling edge of the continent as coastal birds flutter over the marsh, silhouetted against a sunset-streaked bayou, Lana Del Rey crooning on the radio. A bumper sticker on one vehicle reads: "The South is not a lost cause."   

"Everyone thinks of this as the industrial coast, the forgotten coast. But I say, 'Clearly you've never been here,'" stressed McKinney. "We've lost a lot, but what's left is still worth saving." Added Collins, "How would you feel if someone you loved was diagnosed with something that wasn't terminal but was diagnosed as a lost cause? It would break your heart. And who has the right to decide what causes are lost and what causes are still worth saving? I don't believe in lost causes. I only believe in protecting what you love."

The Gulf of Mexico is trying to recover from the wounds of 15 years ago, but there are still unresolved issues and threats to overcome.

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