Occurrence and Cycling of Carbon Monoxide in Marine Coastal Sediments

Abstract

Carbon monoxide (CO) could be used as an energy source for marine microbes, while the biogeochemical cycling of CO remains largely unexplored in marine sediments. We integrated biogeochemical analysis, thermodynamic calculations, and incubation experiments to constrain the production and consumption potential of CO in the coastal sediments of the East China Sea. The concentrations of CO ranged from 98.3 to 333.7 nM and generally increased with depth along the 4.5-m sediment core. Significant correlations were observed between CO and  DIC, DOC, or sulfate, suggesting the control of CO production from organic matter degradation. The calculations of free energy yield indicated that CO oxidation-coupled microbial processes such as sulfate reduction, metal reduction, acetogenesis, and methanogenesis were thermodynamically feasible under in situ conditions. Incubation experiments demonstrated that trace CO could be produced from the addition of organic compounds such as glucose, glycerol, and methanol. In sediment slurries, amended CO were rapidly metabolized. The addition of electron acceptors or inhibitors suggested a large fraction of CO was consumed by sulfate reducers, and to a lesser extent, by methanogens. Collectively, these results revealed the potential of carboxydotrophy as a metabolic mode for diverse microbes living in marine sediments that were previously ignored.