Affected sea turtles and marine mammals are still being brought into care facilities one year after the explosion of British Petroleum’s Deepwater Horizon oil rig in the Gulf of Mexico.

Rescuers so far have collected 1,149 sea turtles, 170 dolphins and three whales: a melon-headed whale, a pygmy sperm whale and a sperm whale.

“We’re still in active recovery efforts for mammals,” said Dr. Michael Ziccardi, DVM, who oversaw rescue and rehabilitation of oiled sea turtles and marine mammals for months after the April 20, 2010, explosion. “At the end of last fall, we made a transition plan that we would implement when we went 60 days without finding a mammal affected by oil, but so far we haven’t gone a full 60 days.”

Ziccardi, an associate professor of clinical wildlife health at the University of California, Davis, Wildlife Health Center, continues to advise the National Oceanic and Atmospheric Administration (NOAA) on response activities, including watching for ongoing impacts to marine mammals.

The largest oil spill in American history, the Gulf disaster began one year ago Wednesday with an explosion on an offshore oil platform about 50 miles southeast of the Mississippi River delta. The accident caused oil to gush from a well located 5,000 feet underwater.

Eleven men were killed in the explosion and 17 injured. By the time the leak was capped three months later, almost 5 million barrels of crude oil had been released, causing extensive damage to marine habitats and crushing the area's tourism and fishing industries.
 
Approximately 48,000 people worked on the response, of which close to 1,000 worked with marine mammals and sea turtles, Ziccardi said. The Gulf catastrophe marked the first time in modern history there has been a large-scale impact to live turtles, he said, noting that previously, the largest documented number of sea turtles affected by an oil spill was 13 hatchlings.

“There was an extremely steep learning curve. What we are learning now is how oil affects these animals and how we can respond better in the future,” Ziccardi said.

Today, 42 turtles that had long-term health issues remain at care facilities in New Orleans and Gulfport, Miss. Rescuers determined that the water was too cold for them to be released immediately. “We had to decide to either wait until the water warms up or ship them to Florida; we are waiting,” Ziccardi said.

More than half of the turtles collected by rescuers — 613 out of 1,149 — were found dead. But of those recovered live, most survived to be returned to the wild.

“Of the 536 live turtles collected, we released 469, we have 42 in care, and 25 died in care,” Ziccardi recounted. “That’s about a 95-percent survival rate. ...

"Just over 10 turtles were released with $4,000 tracking devices; it’s a very expensive undertaking, and the tracking itself is expensive," he went on. "Every released turtle had an Avid microchip tag and was flipper-tagged so that if they become restranded, we'll know if they were brought in during the response.”

In addition to grossly obvious effects of oil on wildlife, rescuers found the spill has had invisible effects as well. For example, of 157 dead dolphins collected, only 10 were visibly oiled outside or inside, Ziccardi said. (A complete necropsy was done on as many animals as possible.)

“We don't know if the oil just wasn’t visible, or if it affected the food chain,” Ziccardi said. “We don't know why they died, but research is now going into those subtle effects. There will be new long-term monitoring projects. ... BP is funding $1 billion of restoration projects so we can start to look at the long-term subtle effects. We hope there isn't a long-term population impact into the future."