Bacteria supplemented their diet to clean up after Deep Water Horizon oil

Aug. 29, 2013 — Bacteria living in the Gulf of Mexico beaches were able to ‘eat up’ the contamination from the Deep Water Horizon oil spill by supplementing their diet with nitrogen, delegates at the Goldschmidt conference will be told today, Friday 30th August.Professor Joel Kostka will tell geochemists gathered in Florence for the conference that detailed genetic analysis showed some of the bacteria thrived on a diet of oil because they were able to fix nitrogen from the air. The research — the first to use next generation sequencing technologies to dig into the detail of how the native beach microbes are metabolising the oil over time — could open the door to much more sophisticated clean up techniques.”Oil is a natural product, made of decayed plants and animals, and so is similar to the normal food sources for these bacteria.” explains Professor Kostka, a microbiologist from Georgia Institute of Technology in Atlanta. “But because oil is low in nutrients such as nitrogen, this can limit how fast the bacteria grow and how quickly they are able to break down the oil. Our analysis showed that some bacteria are able to solve this problem themselves — by getting their own nitrogen from the air.”Professor Kostka worked with Professor Markus Huettel, a biogeochemist from Florida State University, to take more than 500 samples over two years from Pensacola beach in the Gulf of Mexico, starting when the Deep Water Horizon oil slick first came ashore in June 2010. By analysing every gene of every bacteria in the sample, they were able to see which bacteria were present and how they responded as the conditions on the beach changed.The researchers looked at the prevalence of genes which encode for different types of activity — such as nitrogen fixing or phosphorus uptake — to identify exactly how the bacteria were degrading the oil.”By understanding how the oil is degraded by microbes, which microbes do the work, and the impact of the surrounding environmental conditions, we can develop ways to intervene to support the natural clean-up process,” says Professor Kostka. “However, we need to do this in a very measured and targeted way, to avoid long-term, unintended damage to the ecosystem. For example, in the past, nitrogen fertiliser has been sprayed onto contaminated beaches to speed up the work of the bacteria. Our analysis shows that, where bacteria can get this nitrogen naturally, such drastic intervention may not be necessary.”The genetic analysis carried out by Professor Kostka and his colleague Konstantinos Konstantinidis at Georgia Tech can show exactly how the oil-degrading bacteria are working at each part of an affected coastline, making it possible to identify which beaches are most effective at self-cleaning and target mitigation efforts — such as offshore booms — at the most vulnerable areas.But not all the bacteria thrived on a diet of oil. Professor Kostka’s research showed that some bacteria which play an important role in the ecosystem of the beaches experienced a sharp decline following the contamination in June 2010.”There’s a tendency to focus on the short-term, visible effects of an oil spill on the beach and assume that once the beach looks ‘clean’ then all is back to normal,” he says. …

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Large Gulf dead zone, but smaller than predicted

July 29, 2013 — NOAA-supported scientists found a large Gulf of Mexico oxygen-free or hypoxic “dead” zone, but not as large as had been predicted. Measuring 5,840 square miles, an area the size of Connecticut, the 2013 Gulf dead zone indicates nutrients from the Mississippi River watershed are continuing to affect the nation’s commercial and recreational marine resources in the Gulf.”A near-record area was expected because of wet spring conditions in the Mississippi watershed and the resultant high river flows which deliver large amounts of nutrients,” said Nancy Rabalais, Ph.D. executive director of the Louisiana Universities Marine Consortium (LUMCON), who led the July 21-28 survey cruise. “But nature’s wind-mixing events and winds forcing the mass of low oxygen water towards the east resulted in a slightly above average bottom footprint.”Hypoxia is fueled by nutrient runoff from agricultural and other human activities in the watershed. These nutrients stimulate an overgrowth of algae that sinks, decomposes and consumes most of the oxygen needed to support life. Normally the low or no oxygen area is found closer to the Gulf floor as the decaying algae settle towards the bottom. This year researchers found many areas across the Gulf where oxygen conditions were severely low at the bottom and animals normally found at the seabed were swimming at the surface.Graph showing historical hypoxia trends.This is in contrast to 2012, when drought conditions resulted in the fourth smallest dead zones on record, measuring 2,889 square miles, an area slightly larger than Delaware. The largest previous dead zone was in 2002, encompassing 8,481 square miles. The smallest recorded dead zone measured 15 square miles in 1988. The average size of the dead zone over the past five years has been 5,176 square miles, more than twice the 1,900 square mile goal set by the Gulf of Mexico / Mississippi River Watershed Nutrient Task Force in 2001 and reaffirmed in 2008.On June 18, NOAA-sponsored forecast models developed by Donald Scavia, Ph.D., University of Michigan, and R. …

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