The 2010 Deepwater Horizon oil spill in the Gulf of Mexico has been described as the worst environmental disaster in the United States, releasing about of crude oil making it the largest marine oil spill in history. Both the spill and the cleanup efforts had effects on the environment.
The oil spill was called the "worst environmental disaster the US has faced" by White House energy adviser Carol Browner. The spill was by far the largest in US history, almost 20 times greater than the usual estimate of the Exxon Valdez oil spill. Factors such as petroleum toxicity, oxygen depletion and the use of Corexit are expected to be the main causes of damage.
Impact to marine species
Most of the impact was on the marine species. Eight U.S. national parks were threatened and more than 400 species that live in the Gulf islands and marshlands are at risk, including the endangered Kemp's ridley turtle, the green turtle, the loggerhead turtle, the hawksbill turtle, and the leatherback turtle. In the national refuges most at risk, about 34,000 birds were counted, including gulls, pelicans, roseate spoonbills, egrets, terns, and blue herons. A comprehensive 2009 inventory of offshore Gulf species counted 15,700. The area of the spill includes 8,332 species, including more than 1,200 fish, 200 birds, 1,400 molluscs, 1,500 crustaceans, 4 sea turtles, and 29 marine mammals. In a 2011 paper in the journal BioScience, researchers from the University of New Hampshire reported that the spill threatened 39 marine species in addition to the 14 currently under federal protection. Threatened species, the report found, ranged from 'whale sharks to seagrass". Also another impact to marine species was the impact to various food chains. With one break in the chain, the rest of the chain could be impacted greatly.
Harry Roberts, a professor of Coastal Studies at Louisiana State University, has stated that of oil would be enough to "wipe out marine life deep at sea near the leak and elsewhere in the Gulf" as well as "along hundreds of miles of coastline." Mak Saito, an associate scientist at Woods Hole Oceanographic Institution indicated that such an amount of oil "may alter the chemistry of the sea, with unforeseeable results." Samantha Joye of the University of Georgia indicated that the oil could harm fish directly, and microbes used to consume the oil would reduce oxygen levels in the water. The ecosystem, she said, could require years or decades to recover, as with previous spills. Damage to the ocean floor would endanger the Louisiana pancake batfish in particular, whose range is entirely contained within the area affected by the spill.
The actual number of mammal deaths due to the spill may be as much as 50 times higher than the number of recovered carcasses, according to a study published in the Journal Conservation Letters. "The Deepwater oil spill was the largest in US history, however, the recorded impact on wildlife was relatively low, leading to suggestions that the environmental damage of the disaster was actually modest. This is because reports have implied that the number of carcasses recovered... equals the number of animals killed by the spill" stated Rob Williams from University of British Columbia.
Timeline On 22 October 2010, it was reported that miles-long strings of weathered oil had been sighted moving toward marshes on the Mississippi River delta. Hundreds of thousands of migrating ducks and geese spend the winter in this delta. Two years after the Deepwater explosion, migratory birds were found to have carried chemicals from the spill to Minnesota. Preliminary evidence showed the vast majority of the small sample of pelican eggs tested contained "petroleum compounds and Corexit". As of 2 November 2010, 6,814 dead animals had been collected, including 6,104 birds, 609 sea turtles, 100 dolphins and other mammals, and 1 other reptile. According to the U.S. Fish and Wildlife Service, the cause of death had not been determined as of late June. According to NOAA, since 1 January 2011, 67 dead dolphins had been found in the area affected by the spill, with 35 of them premature or newborn calves.
An NOAA study in spring 2012, along with two other studies reported at the same time, suggests that the long-term environmental effects of the spill may have been "far more profound than previously thought". The joint study by NOAA and BP found "many of the 32 dolphins studied were underweight, anemic and suffering from lung and liver disease, while nearly half had low levels of a hormone that helps the mammals deal with stress as well as regulating their metabolism and immune systems". Researchers found that some types of spiders and other insects were far less numerous than before the spill.
During a January 2013 flyover, former NASA physicist, Bonny Schumaker noted a "dearth of marine life" in a radius of 30 to 50 miles (50 to 80 km) around the Macondo well. "Since the fall of 2011, now about 14 months, I see no turtles, few if any dolphins, few if any rays ... few sharks, few bait balls, all of the things we used to see," she commented. This may mean that the wildlife left the area in search of food. "I guess the Gulf of Mexico in these parts is a stinky, dead desert for its previous visitors," Schumaker told NBC news.
Three years after the oil spill, the residual effects were still apparent, with tar balls still found on the Mississippi coast, as well as an oil sheen along a coastal marsh, and erosion on an island in Barataria Bay sped up by the death of mangrove trees and marsh grass.
Corals On February 26, federally funded scientists found damage to deep sea coral several miles from the well. Expedition leader and biologist with Penn State University Charles Fisher said there was "an abundance of circumstantial data" suggesting coral damage is related to the spill. This discovery indicated that the spill's ecological consequences may be greater than was previously officially claimed. "The visual data for recent and ongoing death are crystal clear and consistent over at least 30 colonies; the site is close to the Deepwater Horizon; the research site is at the right depth and direction to have been impacted by a deep-water plume, based on NOAA models and empirical data; and the impact was detected only a few months after the spill was contained."
In March 2012, definitive link was found between the death of a Gulf coral community the size of half a football field and the spill. The scientists wrote: "The presence of recently damaged and deceased corals beneath the path of a previously documented plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems."
Effect to dolphins
In February 2011, the first birthing season for dolphins since the spill, the director of the Institute for Marine Mammal Studies in Gulfport reported that dead baby dolphins were washing up along the Mississippi and Alabama shorelines at about 10 times the normal number for the first two months of the year. "For some reason, they have started aborting or they were dead before they were born; the average is one or two a month. This year we have 17 and February is not even over yet."
From mid-January to late March 2011, scientists counted almost 200 dead dolphins in the Gulf, with another 90 in 2010. After investigating the deaths, NOAA put a gag order on the results, saying that the research is part of a criminal investigation of the spill. Numerous independent scientists said they have been "personally rebuked by federal officials for speaking out of turn to the media about efforts to determine the cause" of the deaths.
In April 2011, one year from the onset of the spill, scientists confirmed that they had discovered oil on dead dolphins found along the Gulf Coast. Fifteen of the 406 dolphins that had washed ashore in the last 14 months had oil on their bodies; the oil found on eight of them was linked to the spill. A NOAA spokesperson said it was "significant that even a year after the oil spill we are finding oil on the dolphins, the latest just two weeks ago." A NOAA study in the summer of 2011 showed dolphins that came in contact with the petroleum were "seriously ill" with drastically low weight, low blood sugar and for some, cancer of the liver and lungs.
In December 2013, the journal Environmental Science & Technology published a study finding that of 32 dolphins briefly captured from 24-km stretch near southeastern Louisiana, half were seriously ill or dying from liver disease, pneumonia, loss of teeth, and one pregnant female was carrying a dead fetus. The animals compared unfavorably with dolphins from an area of the gulf unaffected by the spill. BP said the report, which was the first study of the spill's impact on dolphins, was "inconclusive as to any causation associated with the spill".
On 12 April 2016, a research team reported that 88 percent of about 360 baby or stillborn dolphins within the spill area "had abnormal or under-developed lungs", compared to 15 percent in other areas. The study was published in the April 2016 Diseases of Aquatic Organisms.
Impact on marine life In 2012 "disturbing numbers" of mutated fish were seen in the Gulf. Scientists and fishermen pointed to the spill, the dispersants and chemicals used in its cleanup as the cause of the deformities which include shrimp born without eyes, fish with lesions, fish with oozing sores and, according to a local fisherwoman, "We are also finding eyeless crabs, crabs with their shells soft instead of hard, full grown crabs that are one-fifth their normal size, clawless crabs, and crabs with shells that don't have their usual spikes ... they look like they've been burned off by chemicals". The dispersants are known to be mutagenic. In Barataria Bay, Louisiana, an area "heavily impacted by oil and dispersants", 50% of shrimp were found lacking eyes and eye sockets. Another lifelong fisher-woman reported seeing "fish without covers over their gills and others with large pink masses hanging off their eyes and gills". A 2014 study of the effects of the oil spill on bluefin tuna, published in the journal Science, found that oil already broken down by wave action and chemical dispersants was more toxic than fresh oil.
Prior to the spill, approximately 0.1% of Gulf fish had lesions or sores. A report from the University of South Florida said that many locations showed 20% of fish with lesions, and later expeditions some as high as 50%.
A 2014 paper in the journal Science found that toxins released by the oil spill killed fish by causing cardiac arrest. The study found that even very low concentrations of crude oil can slow the pace of fish heartbeats. The study was conducted by researchers at Stanford University and the National Oceanic and Atmospheric Administration as part of the federal Natural Resource Damage Assessment process required by the Oil Pollution Act. It focused on tuna partly because the spill occurred in an area where Atlantic bluefin tuna were spawning. The effects were considered especially problematic for fish embryos and early developing fish, because the heartbeat changes could affect the development of other organs, including the lungs and liver. BP disputed the study, raising questions about the study and the use of its findings in the damage assessment process. Another peer-reviewed study, released in March 2014 and conducted by 17 scientists from the United States and Australia and published in the Proceedings of the National Academy of Sciences, found that tuna and amber jack that were exposed to oil from the spill developed deformities of the heart and other organs. BP responded that the concentrations of oil in the study were a level rarely seen in the Gulf, but The New York Times reported that the BP statement was contradicted by the study.