The impact of the 2010 BP oil spill in the Gulf of Mexico is far more widespread than previously thought, a study released Monday indicates. Researchers say the spill’s “footprint” -- the range of the marine ecosystem affected by the Deepwater Horizon disaster -- extends twice as far from the site of the well leak than data first revealed.  

Although surface-level oil has largely dissipated, scientists have observed the effect of the spill on seafloor coral reefs several miles from the wellhead and thousands of feet below the surface. Their research widens the spill’s known area of impact to more than 13 miles from its epicenter and to nearly 6,000 feet deep.

"The footprint of the impact of the spill on coral communities is both deeper and wider than previous data indicated," Charles Fisher, a professor of biology at Penn State University in Pennsylvania and lead author of the study, published in the journal Proceedings of the National Academy of Sciences, said in a statement. "This study very clearly shows that multiple coral communities … were impacted by the spill."

BP’s Deepwater Horizon -- a deepwater oil drilling rig 40 miles off the coast of Louisiana -- exploded April 20, 2010, killing 11 crewmen and sparking a fire that could be seen from the mainland. The fire burned for 36 hours before the rig sank to the ocean floor. The resulting oil spill continued until July 15, releasing nearly 5 million barrels, or 210 million gallons, of oil and gas into the environment.

The resulting oil slick covered 30,000 square miles, making it the largest oil spill in history. While measuring the surface impact of the spill was easy enough, gauging the extent of subsurface damage had proved difficult.

“It seems like it’s been a long time [since the spill], but the deep sea is a slow-moving environment,” Fisher told Think Progress. “Things change slowly. So it could be a while before things are fully recognized in the wider Gulf.”

In April, BP, which has long downplayed the severity of the drilling catastrophe, announced it was ending its “active cleanup” of Louisiana’s coast. But the Coast Guard emphasized it would remain in the area to respond to any subsequent reports of oil.

“Let me be absolutely clear: This response is not over -- not by a long shot,” Capt. Thomas Sparks, the federal coordinator for the Deepwater Horizon Response, said in a statement. “[BP’s announcement] does not end cleanup operations, and we continue to hold the responsible party accountable for Deepwater Horizon cleanup costs.”