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Environment: Deepwater oil disaster radically altered microbial communities on Gulf Coast beaches

Oil from BP’s failed Deepwater Horizon drill rig and the Macondo well spread across the ocean in May 2010. PHOTO COURTESY NOAA.

Followup research will determine how long the impacts last

By Summit Voice

SUMMIT COUNTY — Biologists said they were shocked by the dramatic changes they observed in microbial communities along Gulf of Mexico beaches after the 2010 Deepwater Horizon oil disaster.

The study led by by scientists from University of New Hampshire’s Hubbard Center for Genome Studies, sampled sites around Dauphin Island, Ala., and Grand Isle, La., just after the Deepwater Horizon spill began but before oil reached the shore, then again several months later, in September 2010.

“In that short time period, we saw a drastic change in the microbial community,” said University of New Hampshire researcher Holly Bik, “We were shocked at how drastic the change was, pre- and post-spill.”

The researchers’ findings also point to the possibility of lingering but hidden effects of the spill, which is the largest accidental marine oil spill in the history of the petroleum industry.

Other Deepwater Horizon followup studies have shown that oil-derived toxic compounds persist in some Gulf beaches, that zooplankton in the Gulf absorbed oil at a mollecular level, that oysters in the Gulf may be contaminated by heavy metals from spilled oil, and that exposure to the oil results in embryonic developmental defects in fish and other vertebrate species.

“If you turned up at the beach in September and looked around, you would have had no idea there was an oil spill,” Bik said. “Yet our data suggest considerable hidden initial impacts across shallow Gulf sediments that may be ongoing.”

After studying the sediment sample, Bik and W. Kelley Thomas, director of the Hubbard Center for Genome Studies, said the communities of microbial eukaryotes (organisms not visible to the naked eye whose cells contain nuclei)  shifted dramatically from what you would expect on a beach.

Instead of highly diverse communities dominated by nematodes, they found an almost only oil-digesting fungi.

“The fungal taxa that were there were previously associated with hydrocarbons,” Bik said, explaining that the group of fungi sampled post-spill from the Grand Isle sites may use hydrocarbons and thrive in hostile, polluted conditions that appear to be intolerable for other marine fungi.

The researchers used two parallel methodologies – high-throughput gene sequencing to sort the organisms into “piles” by their DNA, and an under-the-microscope taxonomic approach — to evaluate the communities pre- and post-spill. In the taxonomic data examining nematodes, researchers found that the post-spill samples were dominated by more predatory and scavenger nematodes as well as juveniles.

While nematodes and fungi are hardly charismatic and are unlikely to turn up on the dinner table, these little-understood yet abundant organisms are nonetheless important.

“They underpin the entire ecosystem,” Bik said. “If you knock out the base of the food pyramid, you’re not going to have food higher up in the food chain.” Further, they are also important for nutrient cycling and sediment stability.

Ongoing research and sampling will aim to determine whether fungi are thriving and persisting long-term and whether the shift in communities is an ephemeral, seasonal or a more permanent phenomenon.

The use of high-throughput sequencing approaches to characterize changes in microscopic eukaryote communities is a cutting-edge technique for tracking environmental disturbance. “The development of these genomic tools provides a detailed understanding of the biological consequences of such environmental disasters and is the first step toward mindful approaches for mitigation and remediation of this oil spill and those we will face in the future,” says Thomas, who is the Hubbard Professor of Genomics at UNH.

The findings, which analyzed marine sediments from five Gulf Coast sites prior to and several months following shoreline oiling, are published in the June 6, 2012, issue of the journal PLoS ONE. In addition to Bik and Thomas, co-authors were Kenneth Halanych from Auburn University and Jyotsna Sharma of University of Texas, San Antonio.

This research, which is ongoing, was funded through the National Science Foundation’s RAPID program for quick-response research on natural human-caused disasters and similar unanticipated events. More information about the grant is available here: http://www.unh.edu/news/cj_nr/2010/sep/bp14oil.cfm

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