Deep Sea Mining Zone Hosts CO2-Consuming Bacteria
Scientists have discovered that bacteria in the deepest parts of the seafloor are absorbing carbon dioxide and could be an additional food source for other deep-sea life.
Prof. Andrew K. Sweetman from Heriot-Watt University in the U.K. studied bacteria living 4,000 meters below the ocean surface in the Clarion-Clipperton Fracture Zone.
Until now, scientists believed the main source of biomass on the seafloor was the organic matter that floated down towards the depths: dead fish, plankton and other detritus. However, Sweetman made two major findings: “In contrast to similar studies in the north Atlantic Ocean, we found that bacteria and not seafloor animals were the most important organisms consuming organic detritus that floats down towards the ocean floor.
“We also discovered that benthic bacteria are taking up large amounts of carbon dioxide and assimilating it into their biomass through an unknown process. This was completely unexpected.
“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.
“If we upscale our results to the global ocean, our findings reveal that 200 million tons of CO2 could be fixed into biomass each year by this process. 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.”
Sweetman's team found the same activity at multiple study sites separated by hundreds of kilometers.
The Clarion-Clipperton Fracture Zone is a prime area of interest for future seabed (polymetallic nodule) mining. 16 contractors from countries including the U.K., Germany, France and Korea have claimed exploration rights in the region and have begun conducting surveys to gather baseline data on biodiversity and genetic connectivity across their claim areas.
Sweetman is calling for the International Seabed Authority to ensure contractors in this area will implement carbon cycling monitoring as well as biodiversity and genetic studies. “If mining proceeds in the Clarion-Clipperton Fracture Zone, it will significantly disturb the seafloor environment.
“The full-scale mining proposed in the Clarion-Clipperton Fracture Zone could significantly impact benthic ecosystems for decades, perhaps even longer.
“Now that we have shown that novel carbon cycling processes are happening on the seafloor in this region, which may be very significant in terms of the carbon cycle, authorities should insist that hopeful mining contractors study these processes in baseline surveys, impact assessments and monitoring, so that mining-related changes in this important ecosystem process can be identified and tracked.”