<P> 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, 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 . </P> <P> A NOAA study in spring 2012, along with two other studies reported at the same time, suggest 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 . </P> <P> During a January 2013 flyover, former NASA physicist, Bonny Schumaker noted a "dearth of marine life" in a radius 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 . </P> <P> 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 . </P>

How did the gulf oil spill affect the environment