The Deepwater Horizon oil spill is still wreaking havoc on the Gulf of Mexico

The explosion of BP’s Deepwater Horizon drilling platform in the Gulf of Mexico in April 2010 set in motion one of the worst environmental disasters in history. Over 87 days, 134 million gallons of oil –more than 12 times the amount spilled in the 1989 Exxon Valdez disaster – spewed directly into the ocean from the Deepwater Horizon wellhead 5,000 feet below the surface, creating a slick the size of the state of Virginia and covering hundreds of miles of shoreline in oil and other toxic chemicals.

Fourteen years later, with new proposals currently on the table to increase oil and gas extraction on public lands and waters – including expanding the amount of offshore area leased for drilling – it is clear that lessons from the Deepwater Horizon catastrophe have not been learned.

The Gulf of Mexico has not recovered from the disaster, and research is still revealing new and disturbing things about the extent of the damage – damage that is still being felt today, and whose long-term effects we still have no way of predicting.

An unfolding catastrophe for the Gulf of Mexico’s wildlife

The Deepwater Horizon catastrophe was an unusual oil spill, in that the leak came directly from the wellhead, pumping toxic oil directly into the deep ocean. The use of more than a million gallons of oil dispersant in the cleanup operation is believed to have made things even worse, making this oil as much as 52% more toxic, harder to clean up, and more harmful to wildlife than previous spills.

The spill and the cleanup operation devastated wildlife habitats, both in the deep sea and along hundreds of miles of wetlands and beaches. Almost immediately, scientists were reporting mass die-offs of marine species, and research in the 14 years since has made clear just how bad the damage has been.

• According to a 2021 report by the National Oceanic and Atmospheric Administration (NOAA), the spill injured or killed an estimated 100,000 to 200,000 sea turtles, killed tens of thousands of seabirds and trillions of newly hatched fish, and led to the loss of more than four billion oysters, both directly and via the consequent impact on reproduction rates.
• NOAA concluded that the spill likely caused the largest and longest-lasting die-off of bottlenose dolphins ever seen in the Gulf of Mexico, noting that population sizes of bottlenose dolphins in Barataria Bay, Louisiana, and the Mississippi Sound dropped by 52% and 62%, respectively, following the spill. In addition to the many dolphins killed by the oil immediately after the spill, illnesses related to petroleum exposure, notably lung and adrenal diseases, persist in those that survived. The National Wildlife Federation reported that almost all of the 21 species of dolphins and whales in the northern Gulf had “demonstrable, quantifiable injuries” a decade after the spill.
• In 2020, a report by Louisiana’s Coastal Protection and Restoration Authority found many fish and other aquatic species were born with physical disorders, including “cardiac, neural and reproductive dysfunctions; skin lesions; and feeding and swimming disabilities.”
• Oil from the spill contaminated close to half of the habitat of the endangered Rice’s whale – one of the most endangered whale species in the world – in the northeastern Gulf of Mexico, killing an estimated 17% of the Rice’s whale population. Twenty two percent of reproductive females experienced reproductive failure as a result of the spill and 18% of the population are thought to have suffered adverse health effects.

Research conducted in the years since the Deepwater Horizon spill has indicated that initial analyses likely underestimated how far the oil spread.

• A 2020 study by researchers at the University of Miami found that toxic “invisible oil” – concentrated below the surface, undetectable by satellite imagery and toxic enough to destroy 50% of the marine life it came into contact with – actually spread far beyond the impacted area all the way to the shores of Texas and into the current that pulls water from the Gulf toward Miami.
• The same study found that the oil’s reach was 30% larger than previously thought, “potentially exterminating a vast amount of planktonic marine organisms across the domain.”
• A study published in 2024 found “severe” or “moderate” damage to biodiversity across an area of ocean nearly nine times larger than previously reported.

The ecological damage is still being felt today

Fourteen years after the Deepwater Horizon disaster, many of the species impacted by the spill have still not recovered, and with almost 100 million gallons of oil and chemical dispersants thought to remain in the Gulf, marine life continues to suffer. In 2020, a major study of 2,503 fish from 359 locations in the Gulf found elevated levels of polycyclic aromatic hydrocarbons (highly toxic compounds found in oil and petroleum products) in every surveyed fish species, indicating “chronic and widespread oil pollution in this ecosystem.”

Recent research indicates that the ocean floor around the wreckage of the rig is still showing signs of damage; biodiversity in the area remains depleted and the life that persists is struggling.

• A study published in 2024 revealed that coral communities are still showing signs of stress and damage. The corals were weak and brittle, and scarred areas where branches had snapped off were oozing mucus. Some had exposed skeletons, colonized by parasites. Not only were these corals not recovering, the authors observed, “but some of them seemed to be getting worse.” This is bad news not just for the corals, but for the various species that depend on coral for their habitat.
• An expedition in March 2024 found that the area around the wreckage is still relatively empty of life compared to other wrecks, which often over time become habitats themselves. Overall biodiversity is “significantly reduced” from pre-2010 levels and marine life continues to struggle. Crabs, for example, were found “tinted an oily black; many were also missing legs, while others had lesions.”
• Another 2024 study found that 29 out of the 78 fish species endemic to the Gulf of Mexico have not been officially recorded in the region since 2010.
• A 2024 study of meiofauna (tiny, sediment-dwelling marine animals), and the harpacticoid family in particular (a family of copepods – small crustaceans important in the ocean food web), found “severe” or “moderate” impacts to harpacticoid family biodiversity at 35 of 95 locations sampled.
• Recent research has suggested that persistent ecological effects include damage to oyster fisheries, loss of marshlands, and population declines of marine mammals, sea turtles and seabirds. Researchers speaking to National Geographic in 2020 noted that common loons, spotted sea trout and other species are “struggling,” and their populations have still not returned to their pre-spill levels.

Species could take decades to recover – if they ever recover at all

Research over the 14 years since the disaster has indicated that the ongoing impacts of the initial die-offs on species reproduction rates, plus the fact that many of the affected species, such as corals, are slow-growing, it’s likely to be many years yet before the Gulf of Mexico fully recovers, if it ever does.

• A study published in 2015 based on data from monitoring of a sample of pregnant bottlenose dolphins in Barataria Bay found that only 20% of the dolphins produced viable calves, compared to a normal pregnancy success rate of 83%. The Louisiana Coastal Protection and Restoration Authority’s 2020 report estimated that the loss of reproductive adults means that it will likely be at least four decades before the Gulf’s dolphin population recovers.
• The Coastal Protection and Restoration Authority report also estimated that the four square miles of coral reef destroyed by the spill would take between 50 and 100 years to recover to its pre-spill condition, if it recovers at all.

Damage to the shoreline has made the Gulf coast even more vulnerable to storms

The coasts of Louisiana, Texas, Mississippi, Alabama and Florida were all severely impacted by the Deepwater Horizon spill, and the impacts of the oil and its by-products on the shoreline of the Gulf of Mexico are still being felt.

• Research published in 2023 found the average concentration of polycyclic aromatic hydrocarbons in marsh soil to be more than 10 times higher than before the disaster.
• The same study showed that by killing the marsh plants that held the soil in place, the oil accelerated coastal erosion and caused lasting structural damage to the coastline. The rate of marsh loss doubled in the aftermath of the spill and soil strength declined by half, and with oil still present in the marshes, soil strength has not yet fully recovered.
• The continued impact on soil strength is causing “strong erosion events” during storms that were not seen prior to the spill. Analysis of satellite images shows that Hurricane Katrina in 2005 caused significantly less shore loss than much weaker storms that have occurred since the spill, suggesting that the continued effects of the spill have made the coast more vulnerable to storm damage.

Deepwater Horizon: Lessons not learned

As long as we keep drilling for oil in our oceans, the environmental devastation caused when things go wrong will be a fact of life. Even the routine spills that occur practically on a daily basis across the country’s fossil fuel extraction and transportation network can do serious damage. A spill on the scale of the Deepwater Horizon can devastate ecosystems and wildlife for decades.

Not only are proposals for expanding offshore drilling out of step with the prevailing direction of travel toward a clean energy future, but they are also grossly irresponsible – all the more so given that we are still finding out new and disturbing things about what happens when things go wrong, which they inevitably will, sooner or later. Fourteen years after the Deepwater Horizon catastrophe, the Gulf of Mexico has not recovered. We still don’t know if it ever will.