POWRE: Tracing the Source of Phosphorus Using Oxygen Isotopic Ratios

Florida State University, Tallahassee FL

Investigators

Abstract

0073851 Wang Phosphorus plays a decisive role in the biological world and is a limiting-nutrient in many fresh water ecosystems. However, the widespread use of synthetic fertilizers over the past decades has disrupted that balance. The high phosphorus loading due to human activities has been blamed for upsetting ecosystems by causing harmful algal blooms in lakes and rivers as well as in coastal waters. An increased phosphorus influx has also been linked to changes in native flora and fauna in many wetland ecosystems. Determining the source of phosphorus can help in understanding the cycling and transformation of phosphorus in aquatic environments. The goal of this research is to explore whether the oxygen isotope O-18 can be used as a tracer to distinguish "fertilizer" phosphate from "natural" phosphate. This will involve (1) analyzing the stable oxygen isotopic composition of fertilizers, and (2) sampling and analyzing the delta O-18 values of dissolved phosphate in unpolluted aquatic systems. The working hypothesis of this study is that phosphate in fertilizers is primarily derived from marine phosphate and should have delta O-18 values reflecting the marine environment. Because fresh water (in general) is depleted in O-18 relative to seawater, phosphate from the natural phosphorus cycling in fresh water ecosystems is expected to carry delta O-18 signature distinct from the phosphate in fertilizers. This project represents a new research direction for the principle investigator (PI). The support from a POWRE award will allow the PI to develop the necessary preliminary results for a promising avenue of research in the biogeochemical cycling of phosphorus. Since the PI is a tenure-earning assistant professor, the POWRE support will help her establish an active research program on campus that will involve students, assist in her academic advancement and strengthen her case for promotion to associate professor. Also, it will allow her to play a key role in the multi-departmental efforts involving the Departments of Geological Sciences, Oceanography, Chemistry and Biology at Florida State University (FSU) and the National High Magnetic Field Laboratory to develop a strong graduate program in Molecular Ecology and Environmental Science at FSU.