HR: 10:45h
AN: NB42F-02    [Abstracts]
TI: Source and Fate of Phosphorus in a Constructed Wetland in the Northern Everglades: Evidence From Oxygen Isotopes
AU: Li, X
EM: xli@mail.magnet.fsu.edu
AF: National High Magnetic Field Laboratory and Department of Geology, Florida State University, 1800 E Paul Dirac Drive, United States
AU: * Wang, Y
EM: ywang@mail.magnet.fsu.edu
AF: National High Magnetic Field Laboratory and Department of Geology, Florida State University, 1800 E Paul Dirac Drive, United States
AB: High phosphorus influx into wetland ecosystems in the Florida Everglades continues to be a problem. Although the effects of phosphorus (P) loading on plant communities have been well documented, relatively little is know about how those changes affect the biogeochemical processes regulating the nutrient availability and cycling in aquatic cosystems. It has been suggested that oxygen isotopes in phosphate may provide a useful tool for tracing the source of phosphorus in aquatic systems. In this study, we measured the oxygen isotopic composition of total phosphate in sediments collected from an artificial wetland constructed to remove phosphorus from runoff water in the northern Everglades. The d18O values of total phosphate in sediment samples range from 8.3 to 13.3%. These values are very different from those of the phosphate in fertilizers commonly used in this area. These initial data suggest that biologically recycled phosphate is significantly depleted in oxygen-18 compared to the fertilizers and that these sediments are dominated by organic P. Analyses of oxygen isotopic composition of total phosphate in soil samples collected from the Everglades Agricultural Area about 10-12 months after fertilization also indicate the dominance of organic P in the soil, suggesting rapid removal of fertilizer P from the soil through plant uptake and leaching. These data show: 1)d18O decreases from the inflow area (i.e., highly polluted area) to a less polluted area in the constructed wetland; and 2) d18O decreases with depth in the same sediment core. This trend may be explained by less influence of fertilizer at depth and also farther away from the source of P.
DE: 0330 Geochemical cycles
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly