Simulating flow from volcanoes and oil spills

Some time around 37,000 BCE a massive volcano erupted in the Campanian region of Italy, blanketing much of Europe with ash, stunting plant growth and possibly dooming the Neanderthals. While our prehistoric relatives had no way to know the ash cloud was coming, a recent study provides a new tool that may have predicted what path volcanic debris would take.

“This paper provides a model for the pattern of the ash cloud if the wind is blowing past an eruption of a given size,” said Peter Baines, a scientist at the University of Melbourne in Australia who did the study. He published his work in the journal Physics of Fluids.

Volcanic eruptions are an example of what Baines calls an “intrusion.” Other examples include exhaust rising from a chimney, sewage flowing into the ocean, and the oil spilling underwater in the 2010 Deepwater Horizon disaster. In all these events, a fluid rises into a density-stratified environment like the atmosphere or the ocean. As the fluid rises, it is pushed by winds or currents, and this crossflow can cause the intruding fluid to disperse far from its origin.

Scientists have previously modeled intrusions into a completely calm environment, but before Baines nobody had ever attempted to introduce the effect of crosswinds, a necessary step toward making such models more realistic and useful.

Predicting Ash and Oil Flows

Baines thinks his work could be used to estimate how much ash is pouring out of a volcano, or how fast oil is gushing from a hole in the sea floor.

Baines is now working with volcanologists in Britain to apply his model to historic eruptions like the Campanian event and the catastrophic Toba supereruption that occurred around 73,000 years ago in Indonesia. The scientists are hoping to use ash deposits from these volcanoes to develop a sharper picture of the amount and speed of the ejected material.

“Most of what we know about prehistoric eruptions is from sedimentary records,” said Baines. “You then have to try to infer what the nature of the eruption was, when this is the only information you’ve got.”

Baines said his model can also help forecast the deposition patterns of future eruptions. And that should give us a big leg up on the poor Neanderthals.

How the Model Works

To understand how intrusions work in the presence of crossflows, Baines developed what he calls a semi-analytical model. He began with fluid dynamics equations, and then used numerical calculations to arrive at approximate solutions for specifics combinations of source flow and spread rates, and crosswind speed. He found that, under normal wind speeds, the intruding fluid reached a maximum thickness at a certain distance upstream from the source, and thinned in the downstream direction. The distance to the upstream stagnation point depended much more on the rate of source flow than the crossflow speed.

Industry, regulators should take ‘system safety’ approach to offshore drilling in aftermath of Deepwater Horizon accident, says new report

To reduce the risk of another accident as catastrophic as the Deepwater Horizon explosion and oil spill, a new report from the National Academy of Engineering and National Research Council says, companies involved in offshore drilling should take a “system safety” approach to anticipating and managing possible dangers at every level of operation — from ensuring the integrity of wells to designing blowout preventers that function “under all foreseeable conditions.” In addition, an enhanced regulatory approach should combine strong industry safety goals with mandatory oversight at critical points during drilling operations.

The report says the lack of effective safety management among the companies involved in the Macondo Well-Deepwater Horizon disaster is evident in the multiple flawed decisions that led to the blowout and explosion, which killed 11 workers and produced the biggest accidental oil spill in U.S. history. Regulators also failed to exercise effective oversight.

“The need to maintain domestic sources of oil is great, but so is the need to protect the lives of those who work in the offshore drilling industry as well as protect the viability of the Gulf of Mexico region,” said Donald C. Winter, former secretary of the Navy, professor of engineering practice at the University of Michigan, and chair of the committee that wrote the report. “Industry and regulators need to include a factual assessment of all the risks in deepwater drilling operations in their decisions and make the overall safety of the many complex systems involved a top priority.”

Despite challenging geological conditions, alternative techniques and processes were available that could have been used to prepare the exploratory Macondo well safely for “temporary abandonment” — sealing it until the necessary infrastructure could be installed to support hydrocarbon production, the report says. In addition, several signs of an impending blowout were missed by management and crew, resulting in a failure to take action in a timely manner. And despite numerous past warnings of potential failures of blowout preventer (BOP) systems, both industry and regulators had a “misplaced trust” in the ability of these systems to act as fail-safe mechanisms in the event of a well blowout.

BOP systems commonly in use — including the system used by the Deepwater Horizon — are neither designed nor tested to operate in the dynamic conditions that occurred during the accident. BOP systems should be redesigned, rigorously tested, and maintained to operate reliably, the report says. Proper training in the use of these systems in the event of an emergency is also essential. And while BOP systems are being improved, industry should ensure timely access to demonstrated capping and containment systems that can be rapidly deployed during a future blowout.

Operating companies should have ultimate responsibility and accountability for well integrity, the report says, because only they possess the ability to view all aspects of well design and operation. The drilling contractor should be held responsible and accountable for the operation and safety of the offshore equipment. Both industry and regulators should significantly expand the formal education and training of personnel engaged in offshore drilling to ensure that they can properly implement system safety. Guidelines should be established so that well designs incorporate protection against the various credible risks associated with the drilling and abandonment process. In addition, cemented and mechanical barriers designed to contain the flow of hydrocarbons in wells should be tested to make sure they are effective, and those tests should be subject to independent, near real-time review by a competent authority.

The U.S. Department of the Interior’s recent establishment of a Safety and Environmental Management Systems (SEMS) program — which requires companies to demonstrate procedures for meeting explicit goals related to health, safety, and environmental protection — is a “good first step” toward an enhanced regulatory approach. Regulators should identify and enforce safety-critical points that warrant explicit regulatory review and approval before operations can proceed.

Offshore drilling operations are currently governed by a number of agencies, sometimes with overlapping authorities. The U.S. should make a single government agency responsible for integrating system safety for all offshore drilling activities. Reporting of safety-related incidents should be improved to enable anonymous input, and corporations should investigate all such reports and disseminate lessons learned to personnel and the industry as a whole.

Deep below the Deepwater Horizon oil spill

This is a graphic explanation of escaped petroleum dispersion 1,000 meters below the sea. -  EPFL
This is a graphic explanation of escaped petroleum dispersion 1,000 meters below the sea. – EPFL

For the first time, scientists gathered oil and gas directly as it escaped from a deep ocean wellhead – that of the damaged Deepwater Horizon oil rig. What they found allows a better understanding of how pollution is partitioned and transported in the depths of the Gulf of Mexico and permits superior estimation of the environmental impact of escaping oil, allowing for a more precise evaluation of previously estimated repercussions on seafloor life in the future.

The explosion of the Deepwater Horizon rig in April 2010 was both a human and an environmental catastrophe. Getting the spill under control was an enormous challenge. The main problem was the depth of the well, nearly 1,500 meters below the sea surface. It was a configuration that had never been tried before, and the pollution it unleashed after methane gas shot to the surface and ignited in a fiery explosion is also unequalled. Much research has been done since the spill on the effects on marine life at the ocean’s surface and in coastal regions. Now, École Polytechnique Fédérale de Lausanne (EPFL) professor Samuel Arey and the Woods Hole Oceanographic Institute reveal in the advance online edition of Proceedings of the National Academy of Sciences how escaped crude oil and gas behave in the deep water environment.

Into the deep

In June 2010, with the help of a remotely operated vehicle (ROV), Woods Hole scientists reached the base of the rig and gathered samples directly from the wellhead using a robotic arm. The oceanographers also made more than 200 other measurements at various water depths over a 30-kilometer area. These samples were then analyzed with the help of the US National Oceanic and Atmospheric Administration and the dissolution of hydrocarbons was modeled at EPFL. This model showed how the properties of hydrocarbons are important in understanding the wellhead structure and pollution diffusion-how pollution spreads out-in the depths.

From the ROV to the lab

Lab analysis led the scientists to describe for the first time the physical basis for the deep sea trajectories of light-weight, water-soluble hydrocarbons such as methane, benzene, and naphthalene released from the base of the rig. The researchers observed, for example, that at a little more than 1,000 meters below the surface, a large plume spread out from the original gusher, moving horizontally in a southwest direction with prevailing currents. Unlike a surface spill, from which these volatile compounds evaporate into the atmosphere, in the deep water under pressure, light hydrocarbon components predominantly dissolve or form hydrates, compounds containing water molecules. And depending on its properties, the resulting complex mixture can rise, sink, or even remain suspended in the water, and possibly go on to cause damage to seafloor life far from the original spill.

By comparing the oil and gas escaping from the well with the mixture at the surface, EPFL’s Samuel Arey, head of Environmental Chemistry Modeling Laboratory, and colleagues were able to show that the composition of the deep sea plumes could be explained by significant dissolution of light hydrocarbons at 1 kilometer depth. In other words, an important part of the oil spreads out in underwater plumes, so we need a more precise evaluation of previously estimated repercussions on seafloor life in the future. Arey’s methodology offers a better estimation of how pollution travels and the potential deep sea consequences of spills.

“Modeling the environmental fate of hydrocarbons in deep water ecosystems required a new approach, with a global view, in order to correctly understand the impact of the pollution,” explains Arey. This research will have a significant impact on assessments of the environmental impact of deep water oil spills.

Study finds massive flux of gas, in addition to liquid oil, at BP well blowout in Gulf

A new University of Georgia study that is the first to examine comprehensively the magnitude of hydrocarbon gases released during the Deepwater Horizon Gulf of Mexico oil discharge has found that up to 500,000 tons of gaseous hydrocarbons were emitted into the deep ocean. The authors conclude that such a large gas discharge-which generated concentrations 75,000 times the norm-could result in small-scale zones of “extensive and persistent depletion of oxygen” as microbial processes degrade the gaseous hydrocarbons.

The study, led by UGA Professor of Marine Sciences Samantha Joye, appears in the early online edition of the journal Nature Geoscience. Her co-authors are Ian MacDonald of Florida State University, Ira Leifer of the University of California-Santa Barbara and Vernon Asper of the University of Southern Mississippi.

The Macondo Well blowout discharged not only liquid oil, but also hydrocarbon gases, such as methane and pentane, which were deposited in the water column. Gases are normally not quantified for oil spills, but the researchers note that in this instance, documenting the amount of hydrocarbon gases released by the blowout is critical to understanding the discharge’s true extent, the fate of the released hydrocarbons, and potential impacts on the deep oceanic systems. The researchers explained that the 1,480-meter depth of the blowout (nearly one mile) is highly significant because deep sea processes (high pressure, low temperature) entrapped the released gaseous hydrocarbons in a deep (1,000-1,300m) layer of the water column. In the supplementary online materials, the researchers provide high-definition photographic evidence of the oil and ice-like gas hydrate flakes in the plume waters.

Joye said the methane and other gases likely will remain deep in the water column and be consumed by microbes in a process known as oxidation, which en masse can lead to low-oxygen waters.

“We’re not talking about extensive hypoxic areas offshore in the Gulf of Mexico,” Joye explained. “But the microbial oxidation of the methane and other alkanes will remove oxygen from the system for quite a while because the time-scale for the replenishment of oxygen at that depth is many decades.”

Leifer added that some of the larger gaseous hydrocarbons documented, such as pentane, have significant health implications for humans and potentially for marine life.

The study concludes that separating the gas-induced oxygen depletion from that due to liquid hydrocarbons is difficult, absent further research, because all hydrocarbons contribute to oxygen depletion. Therefore, documenting the total mass of hydrocarbons discharged is critical for understanding the long-term implications for the Gulf’s microbial communities, food chain and overall system.

Joye’s team examined samples from 70 sites around the leaking wellhead during a research cruise aboard the R/V Walton Smith during late May and early June of 2010. They combined their data with estimates of the volume of oil released to arrive at a figure that allows scientists to quantify, for the first time, the gas discharge in terms of equivalent barrels of oil. They calculated a gas discharge that’s the equivalent of either 1.6 to 1.9 or 2.2 to 3.1 million barrels of oil, depending on the method used. Although the estimate reflects the uncertainty still surrounding the discharge, even the lowest magnitude represents a significant increase in the total hydrocarbon discharge.

“These calculations increase the accepted government estimates by about one third,” MacDonald said.

The ever-shifting small-scale currents in the Gulf likely have dissipated the plumes and the low oxygen zones associated with them, Joye said, making them difficult if not impossible to find at this point in time. Although gliders are a new platform being used, scientists typically search for subsurface features by dropping instruments from research vessels, a process that’s analogous to looking for a feature on the Earth’s surface by randomly dropping instruments from a height of 1,500 meters (about 5,000 feet) in the atmosphere.

“It’s like searching for a needle in the haystack,” Joye said. “We may never know what happened to all of that gas.”

Joye cautioned against assuming that microbes will rapidly consume the gases released from the well. Undoubtedly, the methane is a feast for them, Joye said, but she also noted that the microbes need nutrients, such as nitrogen, copper and iron. These nutrients are in scarce supply in the Gulf’s deep waters, Joye said, and once they are depleted the microbes will cease to grow-regardless of how much methane is available.

“This study highlights the value of knowledge gained from deep sea hydrate seepage research but also how poorly deep sea processes are understood, such as the role methane hydrates played in forming the deep methane plumes documented by this study,” Leifer said. “Deepwater Horizon underscored how ill-prepared the nation is to respond to future accidents. As a nation, we need to hear this deep sea Sputnik wake-up call.”

Lessons learned from oil rig disaster

The Deepwater Horizon oil rig explosion in the Gulf of Mexico on April 20 triggered one of history’s biggest oil spills at sea. Eleven people lost their lives in the accident. Here the beaches are being cleared. (Photo: BP)
The Deepwater Horizon oil rig explosion in the Gulf of Mexico on April 20 triggered one of history’s biggest oil spills at sea. Eleven people lost their lives in the accident. Here the beaches are being cleared. (Photo: BP)

When interviewed by the BBC, the now retired BP boss Tony Hayward admitted to his company’s insufficient response to the Deepwater Horizon rig accident in the Gulf of Mexico. Could the company have been better prepared for what turned out to be one of the biggest oil disasters in history?

“We were making it up day to day,” Hayward said of BP’s rescue plan. Together with chairman of the board, Carl-Henrik Svenberg, he was held responsible for 11 dead and 17 injured workers. According to the New York Times, five million barrels of oil leaked into the ocean outside the coast of Louisiana between April and August 2010.

A lack of safety procedures was identified by the oil spill investigation commission, set up by President Barack Obama, as a determining factor behind the disaster. The three companies involved in the accident – BP, Transocean and Halliburton – were all accused of having cut corners in order to complete the well. At the time of the blow-out, this job was five weeks behind schedule. Five survivors talked to CNN about a corporate culture in which safety warnings were routinely ignored.

“Major accidents such as the Deepwater Horizon disaster in the Gulf of Mexico could also happen in the North Sea,” says Preben Lindøe, professor of societal safety and security at the University of Stavanger, Norway.

“But strong, organizational barriers between the oil industry, trade unions and the Petroleum Safety Authority Norway reduce the risk,” he adds.

Together with his colleague, associate professor Ole Andreas Engen, he is part of the Robust Regulation in the Petroleum Sector team. The four-year research project, funded by the Norwegian Research Council, also involve the independent research group Sintef and the University of Oslo, in addition to legal expertise affiliated with Boston university.

Different practice

The researchers compare oil industry regulation in the USA, Great Britain and Norway.

“There are hardly any unions in the Gulf of Mexico. Tripartite collaboration, as it is practiced on the Norwegian continental shelf, is therefore impossible,” says Lindøe.

The US regulator, Minerals Management Service, carries out inspections based on a fairly meticulous body of rules. Inspectors are transported to offshore installations, equipped with long and detailed check lists.

By comparison, Norwegian regulation is based on internal control. The authorities thereby rely on the companies administering their safety work themselves. While the Norwegian model is based on trust – built up over time – and the sharing of experience and information, the situation in the US is almost the opposite, according to Lindøe.

“The reason this model has succeeded in Norway, is because the parties have been able to fill the concept of internal control with substance. Both employers and unions are involved in developing industrial standards and good practice which can be adhered to,” he says.

Close shave in the North Sea

But recent near-accidents in Norway may potentially have become disasters. In May 2010, Norwegian oil major Statoil had problems during drilling operations at its Gullfaks field in the North Sea. While drilling a well from the Gullfaks C installation, gas entered the well and reached the platform deck. According to the company’s investigation report, only luck prevented the incident from becoming a much more complicated subsea blowout.

The Petroleum Safety Authority shared this conclusion, and pointed out that the incident could easily have evolved into a disaster. It issued four enforcement notices to Statoil, and the company was reported to the police by environmental group Bellona. International media compared the Gullfaks incident to the Deepwater Horizon accident.

“The public’s attention is triggered by such incidents, and we are made aware of society’s unpredictability. When perceived threats are referred to by the media, societal safety is pushed up on the agenda. The attention paid to this subject varies, which lies in its nature. When safety work succeeds, its success is proved by the non-occurrence of serious incidents. When nothing happens, we may become less attentive and sloppier in adhering to routines and procedures,” says Ole Andreas Engen.

“When attention fades, accidents happen more easily, and are followed by increased awareness. Societal safety is thus a perpetual Sisyphus effort. It is a big challenge for all organizations to maintain a high level of safety awareness over time,” he says.

Robust regulation

The researchers point to another example: A gas leak at the North Sea field Snorre in 2004, when an accident equivalent to Deepwater Horizon was only a spark away. But in spite of a number of near-accidents, Norwegian regulation is still more robust than the US’.

The petroleum industry in Norway has gone through several critical phases in its history. Gradually, the parties involved have learned to trust each other. A robust system like this is able to withstand a blow. This is not the case in the USA, where the authorities have a much more difficult task in monitoring regulations. There are strict requirements for new regulations to undergo cost-benefit analyses, which must be submitted to the President’s office, the researchers explain.

Moreover, the regulation of safety and the work environment is divided between two governmental agencies. The US Coast Guard is the controlling authority of personnel safety on offshore platforms, says Lindøe.

“Workers don’t enjoy the same legitimacy with regard to their role in safety work as they do in Norway,” he adds.

According to Lindøe and Engen, it is common practice in the US to look for scapegoats, and pin the blame for accidents on them, instead of changing the systems. In Norway, the parties are more likely to come together to find out how systems and routines may have contributed to an employee making a mistake. The researcher sum up the lessons learned after the Gulf of Mexico disaster:

“The Deepwater Horizon accident has uncovered some evident weaknesses within US safety regulation. The Government being restrained from intervening directly with the industry is one of them. To the Norwegian industry, this accident and the near-accident on Gullfaks C, should serve as reminders of the importance of maintaining the foundation pillars of the Norwegian safety management system: Effective and well qualified authorities, and clear guidelines for cooperation and trust between the parties,” Lindøe concludes.

Oil remains below surface, will come ashore in pulses

Gregory Stone, director of LSU’s WAVCIS Program and also of the Coastal Studies Institute in the university’s School of the Coast & Environment, disagrees with published estimates that more than 75 percent of the oil from the Deepwater Horizon incident has disappeared.

Stone recently participated in a three-hour flyover of the affected area in the Gulf, where he said that subsurface oil was easily visible from overhead.

“It’s most definitely there,” said Stone. “It’s just a matter of time before it makes itself known again.”

Readings from WAVCIS indicate that the direction of the ocean currents near the middle and bottom of the water column are aimed offshore; in other words, this submerged oil will be pushed out to sea, where it will then rise higher into the water column and be washed onto land, particularly during storms.

“It is going to come on shore not consistently, but rather in pulses because it is beneath the surface,” he said. “You may get one or two, maybe even five or 10 waves coming ashore with absolutely no oil ? but eventually, it’s going to come ashore.” He also cautions that whatever oil doesn’t remain suspended in the water column may simply sit atop the seafloor, waiting to be mixed back into the currents.

“It will simply be stirred up during rough seas or changing currents and reintroduced into the water column,” he explained.

Another timely concern is hurricane season since September is generally one of the most active months of the year. “Storm surge, when combined with storm waves from a hurricane, could stir up this submerged oil and bring it – lots of it – onshore and into the wetlands,” Stone said. “Even a tropical storm could result in more oil on the shoreline. And that’s a reality we need to consider and be prepared for.”

Formally known as the Wave-Current-Surge Information System, WAVCIS is based off of a network of buoys, oil platforms sensors and ADCPs, or Acoustic Doppler Current Profilers, in the Gulf of Mexico. The ADCPs are exceptionally sensitive. Housed on the seafloor, they send acoustic signals up to the surface of the water, measuring the entire water column for everything from current direction to speed and temperature. It’s also integrated with the National Data Buoy Center, or NDBC, system, providing researchers worldwide with a comprehensive look at the Gulf environment, which is an invaluable research tool during the inevitable hurricane season, and also during disasters such as the Deepwater Horizon tragedy.

“WAVCIS is among the most sensitive ocean observing systems in the entire nation,” said Stone. “We measure a wide variety of physical parameters at the water surface, water column and on the sea bed. This information is extremely helpful in predicting or determining where the oil is – and where it’s going to go. Because our information is updated hourly and available to the public, our lab has played a primary role in providing facts about the situation surrounding the oil’s movement and location.”

Stone, whose experience with WAVCIS has spanned everything from natural to manmade disasters, knows that only time will tell the severity of the oil’s impact.

“This is a long term problem. It’s not simply going to go away. I was in Prince William Sound 10 years after the Exxon-Valdez event, and when I lifted up a rock, there was still residual oil beneath it,” he said. “Thus, the residence time of oil in the coastal environment can be substantial, although ecosystem conditions along the northern Gulf are very different and will likely recover quicker than in Alaska. We here at WAVCIS can at least track Gulf conditions to monitor the situation as closely as possible.

Study shows deepwater oil plume in Gulf degraded by microbes

In the aftermath of the explosion of BP’s Deepwater Horizon drilling rig in the Gulf of Mexico, a dispersed oil plume was formed at a depth between 3,600 and 4,000 feet and extending some 10 miles out from the wellhead. An intensive study by scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) found that microbial activity, spearheaded by a new and unclassified species, degrades oil much faster than anticipated. This degradation appears to take place without a significant level of oxygen depletion.

“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,” says Terry Hazen, a microbial ecologist with Berkeley Lab’s Earth Sciences Division and principal investigator with the Energy Biosciences Institute, who led this study. “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.”

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,” Hazen says. “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.”

The results of this research were reported in the journal Science (August 26, 2010 on-line) in a paper titled “Deep-sea oil plume enriches Indigenous oil-degrading bacteria.” Co-authoring the 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 May 25, 2010.

At that time, the deep reaches of the Gulf of Mexico were a relatively unexplored microbial habitat, where temperatures hover around 5 degrees Celsius, 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,” Hazen says. “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.”

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 May 25 and June 2, 2010. Sample analysis was boosted by the use of the latest edition of the award-winning Berkeley Lab PhyloChip – a unique 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-percent while within the plume it was 59-percent.

“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,” Hazen says. “There’s not enough iron to form more of these enzymes, which would degrade the carbon faster but also consume more oxygen.”