BAY JIMMY, La. -- Scientists judge the overall health of the Gulf of Mexico as nearly back to normal one year after the BP oil spill, but with glaring blemishes that restrain their optimism about nature's resiliency, an Associated Press survey of researchers shows.

More than three dozen scientists grade the Gulf's big picture health a 68 on average, using a 1-to-100 scale. What's remarkable is that that's just a few points below the 71 the same researchers gave last summer when asked what grade they would give the ecosystem before the spill. And it's an improvement from the 65 given back in October.

At the same time, scientists are worried. They cite significant declines in key health indicators such as the sea floor, dolphins and oysters. In interviews, dozens of Gulf experts emphasized their concerns, pointing to the mysterious deaths of hundreds of young dolphins and turtles, strangely stained crabs and dead patches on the sea floor.

The survey results mirror impressions Jane Lubchenco, the head of the National Oceanic and Atmospheric Administration, gave on the health of the Gulf in an interview with the AP Thursday.

The Gulf is "much better than people feared, but the jury is out about what the end result will be," she said. "It's premature to conclude that things are good ... There are surprises coming up -- we're finding dead baby dolphins."

Just as it was before the April 20 accident when the Deepwater Horizon oil rig exploded, ultimately spewing 172 million gallons of oil, the Gulf continues to be a place of contradictions: The surface looks as if nothing ever happened while potentially big problems are hidden deep below the surface, in hard-to-get-to marshes and in the slow-moving food web. Some may not even be known for years.

"When considering the entire Gulf of Mexico, I think the natural restoration of the Gulf is back to close to where it was before the spill," said Wes Tunnell at Texas A&M University, who wrote a scientific advisory report for the federal arbitrator who is awarding money to residents and businesses because of the oil spill. Tunnell's grades are typical. He says the Gulf's overall health before the spill was a 70; he gives it a 69 now.

If that pre-spill grade isn't impressive, it's because the Gulf has long been an environmental victim -- oil from drilling and natural seepage, overfishing, hurricanes and a huge oxygen-depleted dead zone caused by absorbing 40 percent of America's farm and urban runoff from the Mississippi River.

Today, a dozen scientists give the Gulf as good a grade as they did before the spill.

One of those is Louisiana State University professor Ed Overton, a veteran of oil spills. He described a recent trip to Gulf Shores, Ala.: "I walked a half-mile down the beach and there wasn't a tar ball in sight. It was as pretty as I've ever seen it."

In the survey, some categories, such as red snapper and king mackerel, even average out to higher grades than before the spill, mostly because months of partial fishing bans have helped populations thrive.

While that sounds good, the average grades for the sea floor plunged from 68 pre-spill to a failing grade of 57 now. Dolphins initially seemed to be OK, but as more carcasses than usual kept washing up -- almost 300 since the spill -- the grade fell to 66, compared to a pre-spill 75. Oysters, always under siege, dropped 10 points, crabs dropped 6 points. And the overall food web slid from 70 before the spill to 64 now.

"Everything may be fine in some places, but definitely not fine everywhere," said University of Georgia researcher Samantha Joye who found dead patches of oiled sea bottom in expeditions near the busted well where 11 men lost their lives. "The oil isn't gone; it's just not where we can see it."