Waves breaking on the shore in Orange Beach, Ala., leave behind an oily residue. Mayor Tony Kennon expects BP to restore the town's beaches to sugar white condition. Debbie Elliott/NPR hide caption

itoggle caption Debbie Elliott/NPR

Retired Coast Guard Adm. Thad Allen testifies Monday before the commission investigating the Gulf of Mexico oil spill. Though Allen was the government's leader of the spill response, he acknowledged it was not always clear to the public who was in charge. Mark Wilson/Getty Images hide caption

itoggle caption Mark Wilson/Getty Images

Bayou Bienvenue in New Orleans is an example of south Louisiana’s wetland loss. Fifty years ago, this was a productive freshwater marsh with cypress and tupelo trees. Today, stumps are all that remain, as saltwater has encroached inland. Debbie Elliot/NPR hide caption

itoggle caption Debbie Elliot/NPR

A core sample from the seafloor of the Gulf of Mexico shows a 2-inch layer of oily material. Researchers are finding oil on the seafloor miles away from the blown-out BP well.  Though researchers have yet to chemically link the oil deposits to the BP well, "the sheer coverage here is leading us all to come to the conclusion that it has to be sedimented oil from the oil spill because it's all over the place," says one scientist. Courtesy of Samantha Joye hide caption

itoggle caption Courtesy of Samantha Joye

A key piece of evidence in the Deepwater Horizon investigation — the blowout preventer — was raised to the surface on Saturday and has yet to be closely examined. The failed mechanism, along with the well cap, was put on a vessel in the Gulf. Petty Officer 1st Class Thomas M. Blue/U.S. Coast Guard/Getty Images hide caption

itoggle caption Petty Officer 1st Class Thomas M. Blue/U.S. Coast Guard/Getty Images

Mote Marine Laboratory in Sarasota, Fla., took in many animals that were displaced or oiled by the oil spill in the Gulf of Mexico. Above, a Kemp's ridley turtle recovers in a tank at Mote. Christopher Joyce/NPR hide caption

itoggle caption Christopher Joyce/NPR