Deepwater Horizon’s Impacts Found in Bacteria
Deepwater Horizon’s Impacts Found in Bacteria
By Brandon Keim
Nobody’s going to shed a tear for an oiled microbe, but the Deepwater Horizon’s impacts include bacteria, underscoring just how subtle and fundamental the blowout’s ecological consequences may be.
The findings, based on comparisons of microbial flux before and after oil washed ashore, are not a final analysis. It’s too soon to say how long-lasting those fluctuations were, or what they meant to other creatures. Instead they’re a starting point, an early observation in research that will continue for years, even decades.
“While visible damages are evident in the wildlife populations and marine estuaries, the most significant effect may be on the most basic level of the ecosystems: the bacterial and plankton populations,” wrote researchers in a study Feb. 28 in Nature Precedings. “Abrupt and severe changes in the microbial metabolism can produce long-term effects on the entire ecosystem.”
Led by biologist William Widger of the University of Houston, the researchers sequenced DNA from near-shore water and beach-soil samples gathered before and after oil arrived in Gulfport, Mississippi, and Grand Isle, Louisiana, following the blowout last spring.
By cross-referencing the DNA to microbe gene databases, they identified populations of bacteria and how they changed. Vibrio cholera, the bug that causes cholera, spiked upward after the spill. So did Rickettsiales, an order of bugs whose diseases include typhus and spotted fever.
Populations of Synechococcus, a typically ubiquitous photosynthesizing bug, collapsed. Communities of Archaea — the lesser-recognized microbial kingdom — also underwent radical makeovers.
The new analyses are not meant to be exhaustive. Most species of ocean-dwelling microbes have not yet been identified. Rather, they’re a diagnostic snapshot that wouldn’t have existed even a decade ago, before the advent of faster, cheaper gene sequencing and a rising appreciation of bacteria’s ecological importance.
“Microbial communities are an essential but vulnerable part of any ecosystem. The basic metabolic activities of microbial communities represent the fundamental status of any environment,” wrote Widger’s team.
Andy Juhl, a Columbia University plankton ecologist who was not involved in the study, cautioned against drawing premature conclusions. “I would take the findings that oil resulted in these changes in microbial composition as a plausible hypothesis,” he said. “Further work may support or refute that hypothesis.”
Juhl’s assessment is in keeping with scientific debate over a growing body of research into exactly what poured and bubbled from the Deepwater Horizon wellhead, and what it meant to the Gulf’s already-troubled ecologies. The research is still in its early stages, painstakingly gathered and deliberated — as it will be for years to come — even as BP has reneged on restoration agreements, arguing that the damage wasn’t so bad after all.
In mid-February, researchers led by University of Georgia biogeochemist Samantha Joye concluded that up to 40 percent of hydrocarbons released by the blowout came in the form of methane gas. Its fate remains unknown, and vast methane pockets could still be floating through the Gulf, they said.
Those findings were criticized as relying on outdated data by oceanographers John Kessler and David Valentine, who a month earlier said that the methane had been consumed by deep-sea bacteria.
The disagreement was a standard scientific back-and-forth, but much less debatable were seafloor movies subsequently shown by Joye at the American Association for the Advancement of Science meeting in Washington, D.C. Shot by a robotic submersible vehicle in December, the films showed a Gulf seafloor covered with oil and dead invertebrates.
What all this ultimately means for Gulf ecology is unknown. As for human impacts, the National Institutes of Health announced on March 1 that it’s looking for 55,000 oil cleanup workers to participate in a long-term study of chemical impacts on health.
In the meantime, the oil industry and Gulf lawmakers continue to push for lifting restrictions on deepwater drilling. Kenneth Feinberg, administrator of the $20 billion claims fund established by BP, has said that Gulf ecosystems should be fully recovered by 2012.
“One viewpoint, which is what BP would want us to believe, is that this oil and gas had been naturally dispersed and had a relatively minor effect, and perhaps no long-term impact on the health of the Gulf of Mexico ecosystem. The other point of view is that it killed lots of animals, oiled wetlands and may have long-term ecological impacts, but it’s too early to assess that,” said Ian MacDonald, a Florida State University oceanographer and co-author with Joye of the methane estimates.
“We all hope the first one is correct, but we should try to be very objective about determining what really did happen,” he said.
Widger’s group concluded that “the long-term damage to the ecosystem including the basic food chain is uncertain and requires future research.”
Images: 1) Geoff Livingston, Flickr. 2) Samantha Joye, University of Georgia.
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Citation: “Longitudinal Metagenomic Analysis of the Water and Soil from Gulf of Mexico Beaches Affected by the Deep Water Horizon Oil Spill.” By William R. Widger, Georgiy Golovko, Antonio F. Martinez, Efren V. Ballesteros, Jesse J. Howard, Zhenkang Xu, Utpal Pandya, Viacheslav Y. Fofanov, Mark Rojas, Christopher Bradburne, Ted Hadfield, Nels A. Olson, Joshua L. Santarpia & Yuriy Fofanov. Nature Precedings, February 28, 2011.
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