Scientists say that six months after the largest oil spill in U.S. history, damage to the Gulf of Mexico may be less dramatic than some had predicted.

A new Associated Press poll out Tuesday shows that a group of scientists who studied the Gulf all lowered their rating of the damage. They rated the ecological health of the Gulf a 65 on a scale of 0-100, down from 71 pre-spill. That rating speaks more to the fact that the scientists believed the Gulf of Mexico was in bad shape prior to the spill, rather than implying that the oil spill itself wasn't as serious an event as originally believed.

The spill, scientists are now saying, was severe, but occurred in water already tainted for years by run-off from the Mississippi River, over-fishing and smaller oil spills. The impact from the spill may be much smaller than feared due to the Gulf's already poor ecological health. Scientists are uncertain as to whether the aftermath of the spill will cause permanent damage.

Researchers are shifting their focus from surface damage to deeper waters and the ocean floor. Some worry that oil deep below may cause genetic mutations or weaken some species.

"There's the sense that it's not as bad as we originally feared," Steve Lohrenz, a biological oceanographer with the University of Southern Mississippi, said. "There's still a lot of wariness of what the long-term impact is going to be."