Diagenesis of marine sediments

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Intense biogeochemical cycling, driven by reactions that remineralize organic matter, takes place in the surface layer of the sediments that cover the seafloor. The cycling, fuelled by oxidation of organic matter by oxygen, nitrate, metal oxides, and sulfate, is an important consequence of diagenesis - the processes that bring about change in a sediment as it is buried. Organisms inhabiting sediments mediate diagenetic reactions and promote exchange of solutes and gases across the sediment-water interface. Bottom sediments are thus an imperfect trap for many of the components that settle to the seafloor, some of which may be toxic. Diagenesis impacts both the water column overlying the sediment, to which the remineralization products are returned, and the composition of the solid phase components of the sediment that become sedimentary archives. My long term objective is to understand the effects of diagenesis on biogeochemical cycling and the influence of diagenesis on both sediment-water interactions and burial of paleosignals. The short term objectives fall into three categories: 1) How does bioturbation - excavation, mixing, and irrigation of sediments - influence exchange of solutes across the sediment-water interface during diagenesis? 2) How do the oxygen content of the bottom water and the flux of organic carbon to the sediment influence reaction pathways and accumulation rates of elements whose solubility can change with the redox potential? 3) How does diagenesis affect our ability to use the distribution of manganese in Arctic Ocean sediments for paleochronology? The objectives will be approached via laboratory experiments and diagenetic modelling. Our research provides an essential underpinning for informed stewardship of our changing environment and will improve our ability to interpret sedimentary archives and extract information about the past.