The Deepwater Horizon oil spill may have had a greater impact on the Gulf of Mexico's ecosystems than previously thought, including damage to life nearly a mile beneath the gulf's surface, according to a report released Monday.
Researchers say that coral reef seven miles southwest of the spill and nearly a mile beneath water level showed extensive damage about eight months after the spill. Many researchers believed the spill's ecological damage would be mainly limited to the surface and shallow water, because oil usually floats on the water's surface.
"A simple surface spill would be unlikely to have an impact at this depth," says Chuck Fisher, a Penn State University professor, and one of the authors of the report. But the sheer volume of oil spilled into the gulf—nearly 5 million barrels over the course of three months—and the fact that the spill occurred deep under the ocean's surface, caused "unprecedented" damage to the gulf's ecosystem. Fisher's team visited several coral reefs further afield from the spill that experienced little damage.
"We were lulled into a false sense of security," he says of the other reefs. By the time his team came to the reef seven miles southwest of the spill, "it became apparent within minutes that there was something wrong."
Coral and starfish at the reef showed "widespread signs of stress," including dead specimens, discoloration, and, in the case of the starfish, abnormal behavior.
Fisher and Helen White, a co-author from Haverford College, say it's likely the damage extended to other sea life, but because coral are stagnant and can live for hundreds of years, they are good barometers of the deep sea's ecosystem.
"It's rare you see a bunch of [coral] dead, it's easy to recognize the damage," Fisher says. "We can unequivocally say other animals were exposed [to the oil], but they could have left or died and floated away."
Although thousands of shallow water and surface-dwelling animals were killed by the spill, White says the impact on the ecosystem can last for years, and that it's still too early to measure the long-term effects of the spill.
"Right away, there are pelicans coated in oil and things you can see, but how it impacts the greater food webs can take a much longer time," she says. "I think it's still too early to say that [the gulf] is back to normal." The team has deployed time lapse cameras near the reef to examine its recovery over the coming months and years.
The group studied the reef twice—in November and December of 2010. Although the health of the reefs is likely to slowly improve, Fisher says there was no health improvement between the visits.
"Things happen very slowly in the deep sea, whether it's life or death. One of the surprising things we found when we came back is that it looked almost exactly as it did two months before," he says. "It will be a long time before we know the full effects of the spill."