9415563 INGALL This research will study the effect of bottom water oxygen concentration on seafloor diagenetic processes and elemental fluxes of phosphorous in marine sediments. The focus of the research stems from preliminary data suggesting that the overall burial and preservation of phosphorus in marine sediments is strongly dependent on the concentration of oxygen in waters overlying the sediments. These studies indicate that oxygen depleted bottom waters enhance phosphorus regeneration from sediments, diminishing overall burial efficiency. If this effect can be verified it has important implications for eutrophication in coastal regions and for the long term cycling of P especially during periods of widespread ocean anoxia. Sites overlain by anoxic and oxic bottom waters in the Gulf of Mexico and the greater Puget Sound region will be examined using in situ benthic flux chambers, pore water and sediment measurements. Steady state fluxes of P and associated elements will be determined from in situ benthic chamber experiments. Benthic fluxes will be combined with sediments burial fluxes in order to calculate P burial efficiencies for the different study sites. A major objective of this research is to identify the mechanisms responsible for the burial and preservation of phosphorus and how they may differ in the presence and absence of oxygen. Particular attention will be paid to processes potentially sensitive to changing redox conditions such as the cycling of P by bacteria and dissolved iron. Data gathered during the field and subsequent lab studies will be integrated into a numerical transport reaction model in order to constrain the kinetics of early phosphorus diagenesis. The results will be used to evaluate the potential effects of variations in sedimentary P flux on long term global marine productivity.
