(CNN) -- Scientists have found evidence of "dramatic" damage to deep-sea coral near the site of the Gulf oil disaster, with one biologist describing it as a shocking find that "slapped you in the face."

"This was the first time that anyone has seen a visually compelling indication of impact to deep sea animals in the vicinity of this deep-sea event," said Charles Fisher, a Penn State University biologist and the leader of a government-funded research expedition.

"We have some very compelling circumstantial evidence and that came from this expedition where we were out studying deep sea coral communities we know about, and exploring for new communities."

The research team encountered an apparently "unhealthy" colony of Madrepora -- a hard coral species -- on November 2 at a depth of 1,400 meters. While some in the coral colony appeared normal, others were covered in a "brown material" and were producing "abundant mucous," he said.

The scientists also encountered a community of soft corals nearby that also appeared to be affected. Extensive portions of the coral colonies were either recently dead or dying.

The discovery was made more than six months after an explosion aboard an oil rig sent crude spewing from a BP-owned well deep below the Gulf of Mexico. Researchers found the coral about seven miles southwest of the site of the spill.

Fisher, who called the discovery a "smoking gun," said researchers can't say for certain that the coral died from the oil, noting that dispersants could have been the culprit.

"The next step is to go back out there and look for direct evidence that the oil caused this damage. We're looking for hydrocarbons that could have been fingerprinted," Fisher said.

BP officials could not immediately be reached for comment Saturday.

Ian MacDonald, a professor of oceanography at Florida State University, said the damage is significant because "this is the first indication of just how widespread the damage is."

He wondered whether there is damage that has not yet been discovered.