Bacteria That Absorbs CO2 Has Been Discovered at the Bottom of the Pacific Ocean

Bacteria that absorbs carbon dioxide (CO2) and potentially turns itself into a food source for other sea creatures has been discovered in one of the deepest parts of the Pacific Ocean.

Scientists were studying the ecosystems in the Clarion-Clipperton Fracture Zone (CCFZ), a trench that extends 2.5 miles beneath the surface of the ocean. The area is currently being explored for its deep sea mining potential—contractors from nations including Korea, Germany and the U.K. believe the site to be a promising source of polymetallic nodules, which contain metals like nickel, copper and cobalt. Teams of researchers are now conducting surveys to assess the biodiversity of the CCFZ to understand what the impact deep sea mining might have.

Andrew Sweetman, from the Heriot-Watt University in Edinburgh, U.K., and his colleagues carried out a series of experiments of the sediments located in the CCFZ and discovered something unexpected—bacteria that was consuming huge amounts of CO2. Findings are published in the journal Limnology and Oceanography.

"We ... discovered that benthic bacteria are taking up large amounts of carbon dioxide and assimilating it into their biomass through an unknown process," Sweetman said in a statement. "Their biomass then potentially becomes a food source for other animals in the deep sea, so actually what we've discovered is a potential alternative food source in the deepest parts of the ocean, where we thought there was none."

Before this study, researchers thought the biggest source of biomass on the seafloor was organic matter—like dead fish and plankton—that floated down.

The team has said it is imperative more research into the seafloor biology is carried out before any mining activities begin. If the findings from the study are scaled up to the oceans globally, it could mean 200 million tonnes of CO2 is being turned into biomass every year. "This equates to approximately 10 percent of the CO2 that the oceans remove each year, so it's possibly an important part of the deep-sea carbon cycle," he said. "We found the same activity at multiple study sites separated by hundreds of kilometres, so we can reasonably assume this is happening on the seabed in the eastern CCFZ and possibly across the entire CCFZ."

In an email interview with Newsweek, Sweetman said each mining contract could disturb hundreds of square miles of seafloor every year. "Small scale disturbance experiments that have been carried out in the abyss have shown limited recovery of animals and microbes over long periods," he explained. "Therefore deep-sea mining may significantly impact seafloor microbes that are actively removing CO2. If a significant amount of CO2 is removed each year by the microbial communities within mining areas, mining may inadvertently affect important ecosystem services in the deep sea."

Sweetman is now leading a project to understand what impact disturing this ecosystem could have on the climate more widely. "We need to explore this process in greater detail," he said. "At present, we don't know where the energy is coming from for CO2 fixation, and what microbes are fixing C into their biomass. Once we've figured this out, we can start interrogating the available data on microbial diversity in the deep-sea to assess where this process is happening in the ocean."

The findings follow another study carried out last year where scientists discovered bacteria in a lake located deep beneath the West Antarctic ice sheet was consuming methane—an extremely potent greenhouse gas. Researchers found the bacteria was digesting methane and preventing it from entering the water and eventually escaping into the atmosphere.

John Priscu, an author on the Anatarctic/methane study, said the findings at CCFZ were surprising. "Clearly, mining activities within this abyssal seafloor region will lead to a cascade of biogeophysical changes to this fragile ecosystem than can influence seafloor carbon transformations for decades that may ultimately alter the elemental balance in the overlying waters," he told Newsweek.