title: Redox chemistry in the phosphorus biogeochemical cycle.
abstract: The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine--PH3--a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C-P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10-20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus biogeochemical cycle, and in turn may impact global carbon cycling and methanogenesis.
authors.affiliation: School of Geosciences, University of South Florida, Tampa FL 33620 mpasek@usf.edu.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Pasek
authors.affiliation: School of Geosciences, University of South Florida, Tampa FL 33620.
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Sampson
authors.affiliation: School of Geosciences, University of South Florida, Tampa FL 33620.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Atlas
mesh_terms: D001272:Atmosphere / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005431:Florida; D055593:Geological Phenomena; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D010720:Phosphines / Q000032:analysis; D017905:Phosphites / Q000032:analysis; D010758:Phosphorus / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D014867:Water / Q000737:chemistry
chemical_list: D010720:Phosphines; D017905:Phosphites; D014867:Water; D010758:Phosphorus; C044646:phosphine
keywords: biogeochemistry; element cycling; phosphonates; phosphorus; redox chemistry