Changes in global nutrient patterns require understanding the connections between water column oxygen levels and the release of sedimentary phosphorus. Nitrogen loadings to the oceans have increased dramatically over the past three decades, while P increases have been more limited. Riverborne and atmospheric NOx inputs have driven several ecosystems into suboxic conditions. The combination of these two factors suggests that coastal marine environments will be increasingly P limited. The degree to which this limits eutrophication depends upon how low oxygen levels shift sedimentary remineralization.
For this reason, researchers from the University of Texas, the Georgia Institute of Technology, and the University of South Carolina plan to assess the role of oxygen concentrations on the release and storage of phosphorus using solid state 31P Nuclear Magnetic Resonance and P-edge X-ray absorption and fluorescence near edge spectroscopy. The methods will allow them to identify and quantify the different organic and polymeric phosphorus phases in sediments, water column particulates, porewaters and dissolved organic fractions from the Cariaco Basin and Effingham Inlet. In addition, the phosphorus composition and concentrations will be mapped within particulates at scales relevant to microbially-mediated storage and degradation mechanisms. Results will be used to (1) determine whether the presence or absence of oxygen has a marked influence on P speciation and remineralization, and (2) if the microscale structure of phosphorus storage within particulates changes during diagenesis, determine what phosphorus species are preferentially remineralized/released from microsites.
As regards broader impacts, besides significantly improving our understanding of phosphorus cycling in the marine environment, this study will provide support and training for one graduate student from Georgia Institute of Technology and one graduate student and one undergraduate student from the University of South Carolina. It is anticipated that results from this research will be incorporated into local middle school demonstrations and a program called ScienceQuest coordinated by the PI from the University of South Carolina. At Georgia Institute of Technology, the graduate student will participate in the Student and Teacher Enhancement Partnership (STEP) that aims to improve earth science education at local middle and/or high schools.
