A Sediment Trap Study to Determine if the Flux of Silver to the Seafloor is Related to Export Productivity

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Intellectual Merit: Since work conducted in the early 1980's, there has been a growing interest in improving our understanding of the relationship between the particle flux of Ag and export productivity in the ocean. Despite tantalizing positive correlations between sedimentary Ag and more traditional paleoproxies, such as organic carbon, opal and biogenic Ba, there has yet to be a comprehensive study undertaken to evaluate in detail the relationship between the flux of particulate Ag and export productivity in the ocean. If the sinking flux of Ag can be shown to reliably track export productivity, as will be evaluated in this study, then the geochemical community will have a new tracer to provide important new insights and constraints on past changes in paleoproductivity. In particular, this project will test the hypothesis that Ag can be used to trace the flux of biogenic particulate organic matter exported from the surface ocean to the sediments; furthermore, this project will evaluate the potential use of Ag as a proxy tracer of past changes in productivity. A secondary objective is to determine whether sedimentary redox conditions affect the accumulation of Ag in sediments. This work will be accomplished by analysis of Ag in a suite of archived sediment trap and sediment samples collected from a range of oceanographic locations. The data obtained from this research will aid in the development of a new paleoproductivity proxy (Ag) that can be utilized to improve paleoceanographic reconstructions. Broader Impacts: In regards to broader impacts, this research will provide the scientific community with a better understanding of the biogeochemical cycling of Ag, an element that is toxic to marine organisms, as well as the cycling of redox-sensitive trace metals. The study will support an early scientist, and provide training for one graduate student and two undergraduate students.