Communities of microbial organisms - including nematode worms, single cell animals called protists, and a variety of fungi - that live in the sediment of beaches on Grand Isle, Dauphin Island and elsewhere along the Gulf of Mexico underwent dramatic changes in the months immediately following the BP Deepwater Horizon oil spill, according to a new study published today in the online scientific journal PLos ONE.

The variety of organisms in beach sand that form one of the lowest links in the Gulf's food chain dropped dramatically several months after the spill, with the remaining species believed to favor those that munch on oily hydrocarbons and are better able to survive the polluted conditions that others species found unlivable, the researchers with the University of New Hampshire's Hubbard Center for Genome Studies and its partners found.

"We went from this very diverse community with an abundance of different organisms to this really (impoverished) community that was really dominated by a couple of fungal species," said Holly Bik, a computational biologist and lead author of the study, who recently moved from the University of New Hampshire to the University of California at Davis.

The results were especially shocking for Dauphin Island, Bik said, because the post-spill samples were taken from what looked like a pristine beach.

"If you dug down in the sand, maybe you could find a discolored layer of oil in the beach, but there were no tarballs," she said. "It was like a ghost town, no tourists, but if you'd been in a media blackout for the previous six months, you wouldn't have even known there had been a spill."

The researchers tested the beach samples for DNA, collecting 1.2 million separate DNA sequences from the different locations. The research was conducted under a grant from the National Science Foundation.

"We go to the beach and take a spoonful of sand and put it in a blender and extract all the DNA from everything that's living in there," said Bik, who also commented on her research as it was occurring on the web at Deep Sea News.

Using chemical tests, the scientists extracted the equivalent of DNA bar codes from the samples and compared them to known codes from the life forms that live on beaches.

In the pre-spill samples, the bar codes showed a rich variety of species. But the post-spill samples from both Dauphin Island and Grand Isle, which had more clear evidence of oiling, were near-matches for the dramatically reduced number of species, Bik said.

"The fungal communities at Grand Isle were very similar to the communities we found on the Alabama coast," she said, and indicated a disturbed microcommunity.

While there seems to be circumstantial evidence that the damage to the microbial communities is the result of the oil, Bik said the researchers haven't ruled out the possibility that the mechanical cleaning of the beach sand in the aftermath of the spill may also be to blame.

Additional research also is needed to determine whether there's been a long-term effect to the coastal microcommunities or the larger ecosystem, Bik said.

"It was this dramatic impact, but without more information, it's hard to place into a bigger context," she said. "A year and a half later, who knows what the community would look like now if we went to the beaches and sampled again."

Bik and her colleagues did take samples last March, a year after the spill, at several of the beaches, but the DNA data from those samples won't be published until the end of the year. Still, Bik said the study provides additional clues to unraveling the short-term and long-term effects of the spill.

"Even though the oil's gone, it might lead to some very long-term and severe implications for the Gulf ecosystem," she said.

(By Mark Schleifstein, The Times-Picayune, 06/06/2012)