Environmental issues oil spills

Their protests were partially successful, and independent researchers soon were given access to oil-soiled locations.

Yet five years after the Deepwater Horizon's explosion killed 11 and unleashed 3.1 million barrels of crude, the picture of the spill's environmental effects remains a work in progress - made difficult at times by legal, scientific and financial realities that continue to make it hard for the public to understand the effects of the nation's worst oil-related environmental disaster.

In an era of pronouncements constantly transmitted in 140-characters, many Americans want a simple answer when it comes to the health of the Gulf. Thumbs up? Or thumbs down?

But scientists say it's not that simple. When the Associated Press recently asked 26 scientists to grade the effects of the spill on about two dozen aspects of Gulf health, they concluded the Gulf was 11 percent less healthy today, dropping from an average 73 to 65 on a scale of 100 to zero.

And citing published results and information released by BP and the federal and state public trustees involved in the official response to the spill, several scientists told NOLA.com | The Times-Picayune that its clear the oil and gas released has had short term effects on natural resources - some of which are recovering.

The big question, however, is the outlook for the long run. Some scientists say there are indications of complex, long-term effects, but warn that five years is too soon to understand their significance.

87-day spill, years of debate over damage

After the April 20, 2010, explosion of the drillship atop BP's Madondo well, crude and natural gas flowed for 87 days, until the government and BP capped the well.

Even before the flow had stopped, the debate over its effects had begun, and it has hardly subsided since. The two opposing views were presented as key evidence to U.S. District Judge Carl Barbier in a New Orleans courtroom earlier this year, as part of the legal process to determining how much BP and its drilling partners should pay in civil fines for their role in causing the spill.

Those views got voiced by scientists Donald Boesch, who testified for the U.S. Justice Department, and Wes Tunnell, who testified for BP.

Boesch, a marine science professor, was the first executive director of the Louisiana Universities Marine Consortium and is now president of the University of Maryland Center for Environmental Science. He also served on the National Commission on the BP Deepwater Horizon Oil Spill, which investigated the disaster afterwards.

Boesch testified that the spill resulted in both actual and potential damages, based on peer-reviewed research.

Among the spill's actual damage, he listed damage to cold-water corals and organisms living in the seabed in the deepwater Gulf; to small planktonic organisms, such as jellyfish, that live in the water just below the Gulf surface; and to floating species ranging from sea turtles to dolphins and birds - including brown pelicans, that live or feed at the surface. The oil and the cleanup eroded or otherwise damaged coastal marshes and mangroves and their associated animals.

The potential effects of the spill included possible damage to other life forms living in the seabed and to fish like red snapper and hake in the deepwater Gulf, Bluefin and yellowfin tuna, mahi-mahi and amberjack, whose eggs and larvae were exposed to oil near the surface. Coastal oysters and the spat - shells put out so oysters can grow in them - could also suffer, Boesch said.

Tunnell, the witness for BP, painted a less drastic picture. A marine biologist and the associate director of the Harte Research Institute of Texas A&M University in Corpus Christi, Tunnell said the spill caused limited or temporary harmful environmental impacts, with the most significant occurring near the wellhead in the deep Gulf and along some beaches and marshes. They included, he said, harm to individual birds and other wildlife.