Two years after an estimated 4.9 million barrels of crude spilled into the Gulf of Mexico from the Deepwater Horizon disaster, there are signs the natural environment is still not back to normal.
The ABC reports dozens of scientific studies are under way to determine the long term impact of the spill.
The Louisiana Universities Marine Consortium is preparing to issue a major report and Dr Paul Sammarco says the results are "sobering".
''My research group, have data regarding the concentrations of petroleum hydrocarbons in seawater in sediment, in marine biota, flora and fauna and in commercial species, seafood such as shrimp and crabs,'' he said.
Dr Sammarco is an authority on coral and spent 12 years working in Australia, most of that time with the Australian Institute of Marine Science in Townsville.
He says the Gulf of Mexico has a natural defence mechanism which helped it cope after the Deepwater Horizon spill.
''There are bacteria which live in the seawater which have evolved here ... through geological times, probably hundreds of millions of years,'' he said.
''They are actually able to 'eat' or metabolise crude oil, petroleum hydrocarbons.''
But Mother Nature could only do so much and the ABC reports fishermen are feeling the pinch.
Louisiana Shrimp Association president, Clint Guidry has called all the docks where boats are unloaded, and they have all report a decline in catches.
"Everyone reported landings that were at least 50% less to 70% less, and that's huge, that's big," he said.
Randy Nunez owns one of the docks.
"I've never seen a brown shrimp season this bad in the whole 42 years I've been in business," he said.
Michelle's Crab Shack owner Michelle Chauncey recently shut her store because the crab catch had declined.
"About a year into the spill, I was unable to get product because the catch was so low," she said.
"Two years into the spill now, into the recovery of it, I am still not operating."
She describes the oil spill compensation programme as an insult.
"I felt like they made me beg for something that I had gladly worked for, for 20 years," she said.
BP America says on its website that as of 1 July, it has paid more than $US7 billion to individuals and businesses.
The company acknowledges there is more work to be done and says BP will continue to meet its commitments in the Gulf.