Microbes Living in Deep Ocean Absorb Carbon Using Chemical Energy

They may not absorb enough carbon to curtail global warming, but the microbes that call the deep ocean home absorb enough of it to merit further study, according to a paper published in the International Society of Microbial Ecology (ISME) Journal.

Lead author of the paper Tim Mattes, an associate professor of civil and environmental engineering at the University Iowa, explained that while most are familiar with the role of trees and grass in absorbing carbon from the air, organisms such as bacteria living in the dark recesses of the ocean hold between 300 million and 1.3 billion tons of carbon.

"A significant amount of carbon fixation occurs in the dark ocean," Mattes said. "What might make this surprising is that carbon fixation is typically linked to organisms using sunlight as the energy source."

However, the researcher explains, while the organisms of the dark ocean may not use sunlight to absorb carbon, they still require an energy source.

"In the dark ocean, carbon fixation can occur with reduced chemical energy sources such as sulfur, methane, and ferrous iron," he said. "The hotspots are hydrothermal vents that generate plumes rich in chemical energy sources that stimulate the growth of microorganisms forming the foundation for deep sea ecosystems."

Along with a team of researchers, Mattes explored the hydrothermal vents located in a volcanic caldera at the active underwater volcano Axial Seamount. Located roughly 300 miles west of Cannon Beach, Ore., and 1,500 meters below the surface, the scientists gathered both data and samples.

Then, using protein-based techniques, the researchers discovered sulfur-oxidizing microorganisms that were also converting carbon dioxide into biomass.

Despite this discovery, according to Mattes "there is no evidence to suggest that they could play any role in mitigating global warming."

Rather, the primary value of the investigation, he says, is that of increasing understanding of how microorganisms living in the dark ocean function in addition to bettering the fundamental knowledge of global biogeochemical cycles.