WASHINGTON, Sept 24 (Reuters) - The muddy deep-sea ecosystem around the massive 2010 Gulf of Mexico oil spill could take decades to recover from the effects of the disaster, researchers reported on Tuesday.
The oil spill from BP Plc's Macondo well had its most severe impact on the ecosystem in an area about nine square miles (24 square km) around the wellhead, the report in the online scientific journal PLoS One said.
Moderate effects were seen at 57 square miles (148 square km). The sea bottom's rich biodiversity was greatly reduced by the oil plume, which was up to 200 yards (183 meters) thick and 1.2 miles (1.9 km) wide, it said.
"Given deep-sea conditions, it is possible that recovery of deep-sea soft-bottom habitat and the associated communities in the vicinity of the DWH blowout will take decades or longer," the report concluded.
The April 20, 2010 disaster aboard the Deepwater Horizon drilling rig killed 11 workers and ruptured the Macondo well, triggering the worst offshore oil spill in U.S. history.
The research was carried out for the National Oceanic and Atmospheric Administration. Paul Montagna, an ecosystems professor at Texas A&M University, said on NOAA's website that normally pollution was found within 300 to 600 yards (meters) of an offshore well.
In the Macondo case, it was found nearly two miles (3.2 km) from the well, he said.
Jeff Baguley, an expert on tiny marine and freshwater invertebrates from the University of Nevada, said on the NOAA website that the samples showed that the dominant group in affected areas had become nematode worms.
The research team included members from University of Nevada-Reno, Texas A&M, NOAA's National Centers for Coastal Ocean Science and representatives from BP.