The oxygen-rich surface waters of the world’s major oceans are supersaturated with methane – a powerful greenhouse gas that is roughly 20 times more potent than carbon dioxide – yet little is known about the source of this methane.
Now a new study by researchers at Oregon State University demonstrates the ability of some strains of the oceans’ most abundant organism – SAR11 – to generate methane as a byproduct of breaking down a compound for its phosphorus.
Results of the study are being published this week in Nature Communications. It was funded by the National Science Foundation and the Gordon and Betty Moore Foundation.
“Anaerobic methane biogenesis was the only process known to produce methane in the oceans and that requires environments with very low levels of oxygen,” said Angelicque “Angel” White, a researcher in OSU’s College of Earth, Ocean, and Atmospheric Sciences and co-author on the study. “In the vast central gyres of the Pacific and Atlantic oceans, the surface waters have lots of oxygen from mixing with the atmosphere – and yet they also have lots of methane, hence the term ‘marine methane paradox.’
“We’ve now learned that certain strains of SAR11, when starved for phosphorus, turn to a compound known as methylphosphonic acid,” White added. “The organisms produce enzymes that can break this compound apart, freeing up phosphorus that can be used for growth – and leaving methane behind.”
The discovery is an important piece of the puzzle in understanding the Earth’s methane cycle, scientists say. It builds on a series of studies conducted by researchers from several institutions around the world over the past several years.
Previous research has shown that adding methylphosphonic acid, or MPn, to seawater produces methane, though no one knew exactly how. Then a laboratory study led by David Karl of the University of Hawaii and OSU’s White found that an organism called Trichodesmium could break down MPn and thus it could be a potential source of phosphorus, which is a critical mineral essential to every living organism.
However, Trichodesmium are rare in the marine environment and unlikely to be the only source for vast methane deposits in the surface waters.
So White turned to Steve Giovannoni, a distinguished professor of microbiology at OSU, who not only maintains the world’s largest bank of SAR11 strains, but who also discovered and identified SAR11 in 1990. In a series of experiments, White, Giovannoni, and graduate students Paul Carini and Emily Campbell tested the capacity of different SAR11 strains to consume MPn and cleave off methane.
“We found that some did produce a methane byproduct, and some didn’t,” White said. “Just as some humans have a different capacity for breaking down compounds for nutrition than others, so do these organisms. The bottom line is that this shows phosphate-starved bacterioplankton have the capability of producing methane and doing so in oxygen-rich waters.”
SAR11 is the smallest free-living cell known and also has the smallest genome, or genetic structure, of any independent cell. Yet it dominates life in the oceans, thrives where most other cells would die, and plays a huge role in the cycling of carbon on Earth.
These bacteria are so dominant that their combined weight exceeds that of all the fish in the world's oceans, scientists say. In a marine environment that's low in nutrients and other resources, they are able to survive and replicate in extraordinary numbers – a milliliter of seawater, for instance, might contain 500,000 of these cells.
"The ocean is a competitive environment and these bacteria apparently won the race," said Giovannoni, a professor in OSU’s College of Science. "Our analysis of the SAR11 genome indicates that they became the dominant life form in the oceans largely by being the simplest.”
“Their ability to cleave off methane is an interesting finding because it provides a partial explanation for why methane is so abundant in the high-oxygen waters of the mid-ocean regions,” Giovannoni added. “Just how much they contribute to the methane budget still needs to be determined.”
Since the discovery of SAR11, scientists have been interested in their role in the Earth’s carbon budget. Now their possible implication in methane creation gives the study of these bacteria new importance.
About Oregon State University: OSU is one of only two U.S. universities designated a land-, sea-, space- and sun-grant institution. OSU is also Oregon’s only university to hold both the Carnegie Foundation’s top designation for research institutions and its prestigious Community Engagement classification. Its more than 26,000 students come from all 50 states and more than 90 nations. OSU programs touch every county within Oregon, and its faculty teach and conduct research on issues of national and global importance.
Angel White | Eurek Alert!
Explosions of Jupiter’s aurora linked to extraordinary planet-moon interaction
25.03.2015 | American Geophysical Union
Rethinking wetland restoration: Smaller wetlands more valuable than previously thought
25.03.2015 | University of Waterloo
In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...
The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.
As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...
When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.
The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe.
Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...
Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.
From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...
25.03.2015 | Event News
19.03.2015 | Event News
17.03.2015 | Event News
27.03.2015 | Agricultural and Forestry Science
27.03.2015 | Materials Sciences
27.03.2015 | Ecology, The Environment and Conservation