Methane related iron reduction processes in sediments: Hidden couplings and their significance for carbon and iron cycles

2026-07-22

About one-third of annual methane (CH4) emissions to the atmosphere originate from natural, nonanthropogenic sources. However, if all the naturally produced methane actually did reach the atmosphere, its levels would increase by an order of magnitude, dwarfing anthropogenic CO2 emissions. Fortunately, natural scavengers of this methane near its production zone limit its release. One of these scavengers, iron (Fe) oxide, can become a major sink for methane when sulfate concentrations are low. Methane-iron couplings in established sediments, however, are poorly understood. Specifically, significant iron oxide reduction has been observed in many aquatic sediments at depths well below its expected redox zone, where methane is produced by methanogenesis, often accompanied by decreases in methane concentrations. These observations challenge our understandings of iron-methane couplings and microbial players in the deep methanogenic zone and their impacts on the carbon, iron and other cycles. I aim in the proposed research to elucidate the unexplored mechanisms of methane-related iron reduction (MERIR) in the methanogenic zone of established sedimentary profiles under various environmental conditions and their impact on global biogeochemical cycles. I will resolve two striking yet unexplained phenomena: (1) the active involvement of aerobic methanotrophs in iron-coupled anaerobic oxidation of methane (AOM), and (2) the unusual reactivity of iron minerals toward reduction that is accompanied by intensive authigenic magnetite precipitation, and the effects of this mineralogy change on sedimentary magnetism. My expertise will enable me to achieve the objectives of this interdisciplinary proposed work using novel approaches from different fields. The project will likely lead to breakthroughs in our understanding of microbial survival strategies, reveal novel pathways for aerobic methanotrophs, and change our perspectives on iron mineral reactivities and sedimentary magnetism.

Israel

2025-11-01