A team of US researchers used underwater vehicles and a process called two-dimensional gas chromatography to match the source of the petroleum hydrocarbons they found with those that emerged from the BP spill.
They found that coral along the sea floor near the well was covered with some sort of brown material and appeared to show signs of tissue damage. A survey of coral 12 miles (20 kilometers) from the Macondo well showed no such damage.
Since sea bed coral lies some 4,000 feet (1,200 meters) below the surface, it is not usually harmed by spills from oil tankers, according to lead study author Helen White, an assistant professor of chemistry at Haverford College in Pennsylvania.
"We would not expect deep-water corals to be impacted by a typical oil spill, but the sheer magnitude of the Deepwater Horizon oil spill and its release at depth make it very different from a tanker running aground and spilling its contents," she said.
"Because of the unprecedented nature of the spill, we have learned that its impacts are more far reaching than those arising from smaller spills that occur on the surface."
More study is needed to determine if the coral will recover, but the findings so far suggest that there was a serious impact on deep sea animal life around the broken well, said lead researcher Charles Fisher, a professor of biology at Penn State University.
"Our ongoing work in the Gulf will allow us to better understand the long-term effects of the spill on the deep sea, and to constrain the footprint of the impact zone for deep-water corals around the Macondo well," he said.
The study is published in the Proceedings of the National Academy of Sciences, and includes experts from Temple University, the Woods Hole Oceanographic Institution, and the US Geological Survey.
The April 20, 2010 explosion on the BP-leased Deepwater Horizon drilling rig killed 11 workers when flammable gas leaked from the well and ignited.
The oil spill that followed blackened beaches in five US states and devastated the Gulf Coast's tourism and fishing industries.
It took 87 days to cap BP's runaway sea floor well as it spewed 4.9 million barrels (206 million gallons) of oil into the Gulf of Mexico.
