Coastal fishermen have enjoyed great fishing since the Deepwater Horizon oil disaster of 2010, but they have lived with the fear of potential long-term impacts to the ecosystem lurking in their minds.

A study released Tuesday on the Public Library of Science Web site indicates there is definite cause for future worry — but not because of the 200 million gallons of crude that spewed unabated into the Gulf of Mexico for over three months.

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Scientists at the University of South Alabama and Dauphin Island Sea Lab, along with biologists from Auburn University. have said their studies indicate that dispersants, including 770,000 gallons sprayed at the broken wellhead on the floor of the Gulf, disrupted the food chain at its most basic levels.

They claimed the 1.8 million gallons of dispersants reportedly used on the oil might have killed plankton, the tiniest creatures that are the basis for the food chain that continues up to all commercial and game fish.

Scientists who have viewed the study said it points toward future problematic effects of the spill. One scientist in Louisiana even labeled the findings "scary."

Brian Crother, a biology professor at Southeastern Louisiana University, told the Associated Press the results are limited because the experiments spanned only five days, but he added that the study is a wakeup call.

"(I)f these guys are on the money, they have pointed to something really disastrous happening in the Gulf," Crother said.

He added that the new study makes clear that the damage to plankton was from dispersant, not oil.

"These guys have shown … that the carbon available from that dispersant is not easily utilized for energy at the bottom of the food chain," he told the AP.

Researchers, who used tanks to simulate the Gulf water column, said the study shows that, within days, the numbers of plant-like phytoplankton and ciliates — plankton that use hairlike cilia to move — increased under an oil slick. But they dropped significantly in the drums with dispersant or dispersed oil, while the numbers of bacteria increased.

"In those tanks, all of the energy seems to get trapped in the bacterial side. There were lots of bacteria left, but no bigger things," said lead researcher Alice Ortmann of the University of South Alabama and Dauphin Island Sea Lab. "It's like the middle part of the food web is taken away,"

Fishermen like guide Sonny Schindler of Shore Thing Charters in Bay St. Louis, Miss., are concerned by the news but are still hoping for the best, which he said is what the Gulf has provided over the past two years.

"Our 2010 season was off the chart for every species," Schindler said. "It went from great to sensational, and has been that way ever since. I haven't seen anything negative, as far as our catches go. I mean, the trout and reds we're catching — and I'm not saying our fishing is better than anyone else's — but just our fishing in our area has been great. I have been thinking we dodged a bullet.

"But, I'm not naïve. I know you can't dump those numbers of gallons of oil and chemicals and dispersants in the Gulf without repercussions. There had to be some break in the food chain at some point. We just have to hope it is not catastrophic."

The concern over long-term effects is rooted in the 1989 Exxon Valdez disaster in Alaska's Price William Sound. Prior to the spill of 11 million gallons, the nation's largest at the time, commercial herring harvest had been at record levels for several years, but the stocks began to collapse by 1993, according to Michael Crosby, senior vice president for research at Mote Marine Laboratory in Sarasota, Fla.

By that time, he said, the number of spawning adult herring was down 75 percent.

"The herring population in Prince William Sound didn't collapse until four years after the Exxon Valdez," Crosby told the AP. "It has never recovered. Never."