<P> 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 4.9 million barrels (210 million US gal; 780,000 m) of crude oil making it the largest marine oil spill . Both the spill and the cleanup efforts had effects on the environment . </P> <P> 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 . </P> <P> 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 . </P> <P> Harry Roberts, a professor of Coastal Studies at Louisiana State University, has stated that 4 million barrels (640,000 m) 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 . </P>

Who was impacted by the bp oil spill
find me the text answering this question