Phosphorus is an essential nutrient for biological production in the ocean. Diagenetic processing and burial efficiency of P in marine sediments exert a major control on marine biogeochemical cycles. Over geologic time, the level of P in the ocean will be controlled to a large extent by its rate of burial in marine sediments. This is crucial to the development of realistic, predictive, biogeochemical models and to the interpretation of the sedimentary record. Detailed solid-phase p data, generated using a new selective sequential extraction (SEDEX) technique, will be collected for a diverse suite of typical marine environments and one river-estuary-delta system (the Mississippi). Phase s responsible for P retention by marine sediments will be identified by examining solid-phase P redistribution with depth in sediments in conjunction with pore water and other solid-phase data. This approach provides insight into the early diagenetic chemical reactions responsible for formation and preservation of these phases. Diagenetic modeling will be used to test interpretations made on the basis of solid-phase and pore water data and to draw further conclusions as to rates of the chemical processes inferred. Comparison of the quantity and chemical nature of solid-phase P to pore water gradients over fine-scale (mm) depth intervals near the sediment-water interface will permit quantification and characterization of P cycling and burial efficiency near this interface. The extent of biogeochemical processing of particulate P during transit across a particular continent-ocean interface will be quantified by comparing solid-phase P speciation in Mississippi River/Estuary suspended matter with that in associated deltaic sediments. Depositional environmental controls on P burial will be generated from which to construct a global marine P budget.
