This study reports evidence of dark oxygen production at the abyssal seafloor in the Pacific Ocean, specifically in the Clarion-Clipperton Zone (CCZ). Through in situ benthic chamber experiments, the researchers found that oxygen levels increased over two days to more than three times the background concentration, attributed to the polymetallic nodules covering the seafloor. The high voltage potentials (up to 0.95 V) on nodule surfaces suggest that seawater electrolysis may contribute to this dark oxygen production. The study also highlights the potential role of nodule surface area in influencing dark oxygen production, with larger nodules showing higher rates. The findings contrast with previous deep-sea benthic oxygen flux studies and suggest that dark oxygen production may provide oxygen for benthic respiration. However, the nonlinear production of oxygen and the relationship with nodule spatial density and type indicate that further research is needed to understand the mechanisms and spatial distribution of dark oxygen production.This study reports evidence of dark oxygen production at the abyssal seafloor in the Pacific Ocean, specifically in the Clarion-Clipperton Zone (CCZ). Through in situ benthic chamber experiments, the researchers found that oxygen levels increased over two days to more than three times the background concentration, attributed to the polymetallic nodules covering the seafloor. The high voltage potentials (up to 0.95 V) on nodule surfaces suggest that seawater electrolysis may contribute to this dark oxygen production. The study also highlights the potential role of nodule surface area in influencing dark oxygen production, with larger nodules showing higher rates. The findings contrast with previous deep-sea benthic oxygen flux studies and suggest that dark oxygen production may provide oxygen for benthic respiration. However, the nonlinear production of oxygen and the relationship with nodule spatial density and type indicate that further research is needed to understand the mechanisms and spatial distribution of dark oxygen production.