NEW ORLEANS -- Half of the oil from the BP oil spill may still be on the floor of the Gulf of Mexico. Those are the findings a new study released by a University of Georgia scientist who claims the chemical used to get rid of the oil didn't do its job.
"You see that piece of rock? That's what made the oyster grow," said Brad Robin during an interview in April with Eyewitness News Investigator David Hammer.
The oysterman still blames the Deepwater Horizon disaster for impacting his annual oyster harvest.
"Some areas are producing more product than others to balance off but east of the river is probably 80 percent off production," said Robin.
Environmental studies continue to show the long-term effects of the massive 2010 BP spill, which spewed more than 3 million barrels of oil into the gulf over 87 days.
A new study released by University of Georgia scientist Dr. Samantha Joye says much of that oil may still be at the bottom of the Gulf of Mexico. She spoke with CBS News a year ago describing mud with an "oily layer" collected from the seafloor.
"This material that's on the sea floor, there's a lot of it. It's widespread and it's sort of sitting there," said Joye.
The marine scientist's study published Monday in the journal Proceedings of the National Academy of Sciences recreated BP's oil clean-up efforts in a lab. The experiment used the same chemical dispersant Corexit 9500 and water from the Gulf of Mexico.
Joye said results show the chemical may not have helped the microbes that eat up petroleum do their job, and she suggests the oil never went away.
"This study and many other studies need to be incorporated when EPA is making its decision for how we respond to disasters, how we respond to oil spills in the Gulf. What are the appropriate practices that leave the environment less impacted?" said Scott Eustis with the Gulf Restoration Network.
The coastal wetland specialist says when large oil spills happen, it's best to prioritize skimming and burning not dispersants. He adds dispersants are harmful to marine and wildlife, stressing the federal regulators like the EPA need to do more to curb its usage.
"It's part of the growing evidence against this as a growing practice. The industry likes it because they often already own the chemicals, they make the chemicals and cosmetically its great if the oil never comes to the surface. They have less of a political problem," Eustis said.
A spokesperson for the American Petroleum Institute (API) says it supports research designed to provide useful information to regulatory agencies, decision makers and affected communities but questions the reliability of the tests done in laboratory conditions. API's Sabrina Fang issued this statement:
"As we continue to evaluate and learn from the unfortunate events in the Gulf five years ago, it is critical that the lessons we learn are based on facts and sound science. API encourages and is supportive of research designed to provide useful, valuable information to regulatory agencies, response decision makers, and affected communities. In fact, industry has and continues to engage with research organizations to advance the state of the science related to all oil spill response options, to include dispersants. However, research, regardless of the sponsoring organization, must ensure that the research that is performed mirrors what is experienced in the real-world. Artificialities introduced in the laboratory environment, when left unexplained, only add confusion to the issue and may result in faulty or inadequate measures being put into place should a spill event occur in the future."