Iron cycling in continental margin sediments and the nutrient and oxygen balance of the ocean
The ICONOX research group evaluates a novel concept of how sedimentary iron cycling controls the ocean’s nutrient and oxygen balance, at present and through geologic time. Iron is an essential micronutrient and commonly regarded as the key-limiting factor for primary production, carbon export and respiratory oxygen consumption in the ocean. The currently observed trend of ocean deoxygenation and acidification promotes dissolution of iron minerals at the seafloor and the resulting increase in iron supply to the ocean may fuel nitrogen fixation, primary production and further oxygen drawdown in a positive feedback loop. By contrast, notorious iron enrichments in sediments of anoxic and sulphidic settings in the geological record indicate that under conditions of extreme ocean anoxia, marine sediments turn into a highly efficient sink for bioavailable iron. The switch from iron release to iron retention and burial likely represents an important, yet poorly constrained linchpin in the long-term cycles of nitrogen and carbon in the ocean. Within the ICONOX project, observational, experimental and numerical approaches are applied to constrain the role of sedimentary iron burial and release in the ocean’s biogeochemical machinery, today and through Earth history.
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