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Study Finds Deepwater Oil Plume in Gulf Stimulating Oil-Degrading Microbes

Hazen
The study found that the dominant microbe in the dispersed Gulf of Mexico oil plume was a new species, closely related to members of Oceanospirillales family. SEM and acridine orange stain inset with distance from source. (Image from Terry Hazen group) Click to enlarge.

In the aftermath of the explosion of BP’s Deepwater Horizon drilling rig in the Gulf of Mexico, a vast, dispersed oil plume formed at a depth between 1,099 and 1, 219 meters (3,600 and 4,000 feet) and extending some 10 miles out from the wellhead. Scientists with the Lawrence Berkeley National Laboratory report that this dispersed hydrocarbon plume has stimulated deep-sea indigenous psychrophilic (cold temperature) γ-proteobacteria that are closely related to known petroleum degraders.

Changes in hydrocarbon composition with distance from the source and incubation experiments with environmental isolates demonstrated faster-than-expected hydrocarbon biodegradation rates at 5 °C. Based on these results, the research team suggests that the potential exists for intrinsic bioremediation of the oil plume in the deep-water column without substantial oxygen drawdown. Their paper was published online 24 August in the journal Science.

Our findings show that the influx of oil profoundly altered the microbial community by significantly stimulating deep-sea psychrophilic (cold temperature) gamma-proteobacteria that are closely related to known petroleum-degrading microbes. This enrichment of psychrophilic petroleum degraders with their rapid oil biodegradation rates appears to be one of the major mechanisms behind the rapid decline of the deepwater dispersed oil plume that has been observed.

—Terry Hazen, principal investigator with the Energy Biosciences Institute

The uncontrolled oil blowout in the Gulf of Mexico from BP’s deepwater well was the deepest and one of the largest oil leaks in history. The extreme depths in the water column and the magnitude of this event posed a great many questions. In addition, to prevent large amounts of the highly flammable Gulf light crude from reaching the surface, BP deployed an unprecedented quantity of the commercial oil dispersant COREXIT 9500 at the wellhead, creating a plume of micron-sized petroleum particles. Although the environmental effects of COREXIT have been studied in surface water applications for more than a decade, its potential impact and effectiveness in the deep waters of the Gulf marine ecosystem were unknown.

Analysis by Hazen and his colleagues of microbial genes in the dispersed oil plume revealed a variety of hydrocarbon-degraders, some of which were strongly correlated with the concentration changes of various oil contaminants. Analysis of changes in the oil composition as the plume extended from the wellhead pointed to faster than expected biodegradation rates with the half-life of alkanes ranging from 1.2 to 6.1 days.

Our findings, which provide the first data ever on microbial activity from a deepwater dispersed oil plume, suggest that a great potential for intrinsic bioremediation of oil plumes exists in the deep-sea. These findings also show that psychrophilic oil-degrading microbial populations and their associated microbial communities play a significant role in controlling the ultimate fates and consequences of deep-sea oil plumes in the Gulf of Mexico.

—Terry Hazen

Co-authoring the Science paper with Hazen were Eric Dubinsky, Todd DeSantis, Gary Andersen, Yvette Piceno, Navjeet Singh, Janet Jansson, Alexander Probst, Sharon Borglin, Julian Fortney, William Stringfellow, Markus Bill, Mark Conrad, Lauren Tom, Krystle Chavarria, Thana Alusi, Regina Lamendella, Dominique Joyner, Chelsea Spier, Jacob Baelum, Manfred Auer, Marcin Zemla, Romy Chakraborty, Eric Sonnenthal, Patrik D’haeseleer, Hoi-Ying Holman, Shariff Osman, Zhenmei Lu, Joy Van Nostrand, Ye Deng, Jizhong Zhou and Olivia Mason.

Hazen and his colleagues began their study on 25 May 2010. At that time, the deep reaches of the Gulf of Mexico were a relatively unexplored microbial habitat, where temperatures hover around 5 °C the pressure is enormous, and there is normally little carbon present.

We deployed on two ships to determine the physical, chemical and microbiological properties of the deepwater oil plume. The oil escaping from the damaged wellhead represented an enormous carbon input to the water column ecosystem and while we suspected that hydrocarbon components in the oil could potentially serve as a carbon substrate for deep-sea microbes, scientific data was needed for informed decisions.

—Terry Hazen

Hazen, who has studied numerous oil-spill sites in the past, is the leader of the Ecology Department and Center for Environmental Biotechnology at Berkeley Lab’s Earth Sciences Division. He conducted this research under an existing grant he holds with the Energy Biosciences Institute (EBI) to study microbial enhanced hydrocarbon recovery. EBI is a partnership led by the University of California (UC) Berkeley and including Berkeley Lab and the University of Illinois that is funded by a $500 million, 10-year grant from BP.

Results in the Science paper are based on the analysis of more than 200 samples collected from 17 deepwater sites between 25 May and 2 June 2010. Sample analysis was boosted by the use of the latest edition of the Berkeley Lab PhyloChip—a novel credit card-sized DNA-based microarray that can be used to quickly, accurately and comprehensively detect the presence of up to 50,000 different species of bacteria and archaea in a single sample from any environmental source, without the need of culturing. Use of the Phylochip enabled Hazen and his colleagues to determine that the dominant microbe in the oil plume is a new species, closely related to members of Oceanospirillales family, particularly Oleispirea antarctica and Oceaniserpentilla haliotis.

Hazen and his colleagues attribute the faster than expected rates of oil biodegradation at the 5 degrees Celsius temperature in part to the nature of Gulf light crude, which contains a large volatile component that is more biodegradable. The use of the COREXIT dispersant may have also accelerated biodegradation because of the small size of the oil particles and the low overall concentrations of oil in the plume. In addition, frequent episodic oil leaks from natural seeps in the Gulf seabed may have led to adaptations over long periods of time by the deep-sea microbial community that speed up hydrocarbon degradation rates.

One of the concerns raised about microbial degradation of the oil in a deepwater plume is that the microbes would also be consuming large portions of oxygen in the plume, creating so-called “dead-zones” in the water column where life cannot be sustained. In their study, the Berkeley Lab researchers found that oxygen saturation outside the plume was 67% while within the plume it was 59%.

The low concentrations of iron in seawater may have prevented oxygen concentrations dropping more precipitously from biodegradation demand on the petroleum, since many hydrocarbon-degrading enzymes have iron as a component. There’s not enough iron to form more of these enzymes, which would degrade the carbon faster but also consume more oxygen.

—Terry Hazen

The PhyloChip technology is licensed exclusively for commercial use to PhyloTech, Inc.

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Comments

Peace Hugger

Tony Hayward can have his life back.

DaveD

Yes, he can have it back....on the Russian Steppes.

ejj

Yet even more evidence, from the mountain of information already collected, that the complete moratorium on deep sea drilling in the gulf should be continued (sarcasm intended).

matt

"EBI is a partnership led by the University of California (UC) Berkeley and including Berkeley Lab and the University of Illinois that is funded by a $500 million, 10-year grant from BP."

Says it all.

Sanity Chk

matt: That doesn't say it all. While research funded by BP should raise concerns about skewed results, these researchers have their careers on the line. Should independent teams find significantly differing results, only then would it be fair to make a claim about the BP funded findings.

ai_vin

"Says it all."

It's more likely that it doesn't say it all and that this is all a lot of half truths. I have no trouble believing there's been some degrading of the oil but into what? Are we just trading long chain molecules for short? Are the bacteria making any toxic byproducts? They did say One of the concerns raised about microbial degradation of the oil in a deepwater plume is that the microbes would also be consuming large portions of oxygen in the plume, creating so-called “dead-zones” in the water column where life cannot be sustained. In their study, the Berkeley Lab researchers found that oxygen saturation outside the plume was 67% while within the plume it was 59%. but how far into it did they really look before someone said "I don't like the way this is going, let's do something else." And what happen to the population boom of bacteria when their food runs out now that the well has been closed?

ejj

Bacteria eats oil & breaks it down into CO2 and methane, which percolate through the water column and into the atmosphere. Dead bacteria disintegrate into food for other sea creatures. I see it kind of like a massive May Fly hatch & die off.

DD

This looked a little sketchy to me too, but I looked up Hazen, and he seems like a solid scientist. He advocated against the dispersants used in the gulf and has made a career of looking at long term impacts of chemical spills. He has patents on microbe proliferation inducing techniques, but seems to feel that adding nutrients to nutrient-poor locations can cause far more damage than doing nothing.

All that said, I haven't read the report in Science, and there could be questionable claims or decisions in it.

However, I do not think that any of this means that it is reasonable to end the moratorium. The report just appears to say (from this synopsis) that an interesting little bug is eating oil, that oxygen levels have dropped, but not as much as expected, and dispersant used may have had something to do with the buildup of the proteobacteria mentioned. What would concern me was if the Oceanospirillales-related bug was accompanied by some form of sulfur-reducing proteobacteria/archea producing hydrogen sulfide. That could be a potentially bad situation for life in and near the Gulf.

danm

Wonderful news! Let's get back to carelessly drilling in water too deep to fix accidents. There was never any damage to gulf waters (sarcasm intended)

ai_vin

Somethings take longer than others;
http://www.evostc.state.ak.us/recovery/StatusIndex.cfm

http://www.evostc.state.ak.us/recovery/lingeringoil.cfm

http://www.evostc.state.ak.us/recovery/longTerm.cfm

http://www.evostc.state.ak.us/recovery/status.cfm

ejj

ai_vin: true - but from what I understand, the Exxon Valdez dumped massive amounts of heavy crude into the waters off Alaska's coast, whereas the gulf oil spill was all light crude. Light crude breaks down much faster via bioremediation.

Coke Machine

As a 7th generation Floridian, and having grown up on Anna Maria Island on Fla's west coast in my youth, this doesn't surprise me. We would get small semi-solid tar balls washed up on our beaches all the time. The gulf seeps the equivalent of 2 Exxon Valdez spills per year, so the bacteria just got the equivalent of a big picnic. While the spill is tragic, and I disagreed with the spraying of dispersants, this spill is just about the equivalent of peeing in an olympic sized pool, and ecologically speaking doesn't even compare with the damage caused by the Exxon Valdez. That spill was heavy crude, not light sweet, those waters were cold, not warm like the gulf (at least when the oil made it near the surface). The grasslands that were impacted are already showing new growth in the damaged areas. I actually think we may have gotten somewhat lucky with this spill. Now they can at least put the spotlight on regulation and some new blowout preventers that really shutdown when they are suppossed to.

Coke Machine

Ai Vin
If they are trading longer chains for short, that is great in my book as shorter chained hydrocarbons have much lower boiling points than longer chained hydrocarbons and will evaporate/diffuse faster. Look at octane with a boiling point of 258F, when that is spilled when refueling your lawnmower, it almost evaporates right away, even though it isn't close to 258F outside. Most of that is diffusion as will most of the loss from the Deepwater Horizon be. You have to get to pentane, a 5 carbon chain to get BP's near room temperature, all the smaller chains are already boiled off at room temp. so as tha majority of this oil nears the surface, the smaller chained hydrocarbons are already gassed off into the atmosphere. While as I posted before, it is tragic, it isn't as bad as the media made it seem.

SJC

I figured the undersea plumes would become an issue sooner or later, out of sight may be out of mind, but you can not just ignore this.

ai_vin

I'm just reminded of an estimate from one source that said "only 26% of the oil spilled remains in the gulf" followed quickly by the qualifying words "as oil."

Which of course means most of the oil could still be there, they're just not calling it "oil" anymore.

ExDemo

Who will reward BP for the fertilizing of the Ocean with a few hundred thousand tons of organic petroleum fertilizer, and sea food?

Twenty years after the Exxon Valdez accident some Biologists wrote that life had not returned to "normal" yet in that Alaskan bay. There is just TOO MUCH life there.

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