A collaborative investigation, spearheaded by researchers from the Scottish Association for Marine Science, has revealed that the abyssal seafloor in the Pacific Ocean, notably its polymetallic nodule-laden areas, is a source of what is termed ‘dark oxygen.’
A polymetallic nodule, collected from the ocean floor, in a lab at Northwestern University. Image credit: Camille Bridgewater / Northwestern University.
Polymetallic nodules, which are naturally occurring mineral accumulations found on the ocean floor, are prevalent across the sediment-covered plains of the world’s oceans.
These formations are predominantly comprised of iron and manganese oxides. Crucially, they also encompass metals like cobalt and rare-earth elements, which are indispensable for numerous cutting-edge and low-carbon energy technologies.
In their recent study, Dr. Andrew Sweetman of the Scottish Association for Marine Science and his team conducted experiments utilizing chambers deployed on the seafloor at depths approaching 4,200 meters. These experiments aimed to quantify oxygen concentration across multiple sites, spanning over 4,000 km within the Clarion-Clipperton Zone in the central Pacific Ocean, a region characterized by abundant polymetallic nodules.
The majority of these experimental setups demonstrated a consistent augmentation of oxygen concentration over a two-day observation period.
Subsequent laboratory analyses were performed, leading the researchers to postulate that the surveyed polymetallic nodules are indeed the origin of the observed oxygen release.
Through the application of numerical simulations, a hypothesis has been put forth suggesting that the electrical properties inherent to the nodules are responsible for the generation of oxygen.
While acknowledging the challenges in estimating the global oxygen output from polymetallic nodules, the researchers propose that this oxygen genesis could sustain deep-seafloor ecosystems, which might face detrimental impacts should these nodules be subjected to mining activities.
“For aerobic existence to emerge on our planet, the presence of oxygen was a prerequisite, and our prior understanding indicated that Earth’s oxygen supply originated from photosynthetic organisms,” stated Dr. Sweetman.
“However, we now understand that oxygen is being generated in the deep sea, an environment devoid of light.”
“Consequently, I believe we must re-examine fundamental questions, such as: At what location could aerobic life have initially arisen?”
The findings have been published in the esteemed journal Nature Geoscience.
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A.K. Sweetman et al. Evidence of dark oxygen production at the abyssal seafloor. Nat. Geosci, published online July 22, 2024; doi: 10.1038/s41561-024-01480-8
This article is based on a press-release provided by Springer Nature and Northwestern University.
