After months of laboratory work, scientists say they can definitively finger oil from BP’s blown-out well as the culprit for the slow death of a once brightly colored deep-sea coral community in the Gulf of Mexico that is now brown and dull.

In a study published Monday, scientists say meticulous chemical analysis of samples taken in late 2010 proves that oil from BP PLC’s out-of-control Macondo well devastated corals living about 7 miles southwest of the well. The coral community is located over an area roughly the size of half a football field nearly a mile below the Gulf’s surface.