SGER: The Oxygen Isotope Ratio of Organic Phosphorus Compounds What controles the isotopic fractionation? A first step towards a new proxy

This P.I. will explore the utility of oxygen isotope systematics in organic P compounds (d18Oop) as a tool for determining community P utilization rate within the euphotic zone. The marine biogeochemical cycle of phosphorus (P) is intricately linked to the atmospheric abundance of CO2 through its role as an important major nutrient and possibly the ultimate limiting nutrient on geological time scales. Unlike nitrogen and silica phosphorus has only one stable isotope and thus isotopic fractionations related to phosphate utilization has not been applied to this system. This would be done by (1) culture experiments geared toward determining the environmental factors (temperature, phosphate concentrations, d18O of growth water and food source, species composition and growth rate) affecting the d18Oop and, (2) experiments designed to evaluate potential artifacts associated with the analytical procedure. This proposal has the potential to provide a unique and powerful tool to investigate present and past P utilization and cycling, and how this might have changed in space and time and in relation to global climate change.