HR: 0800h
AN: B21C-0899    [Abstracts]
TI: Distribution and Turnover of DOC in Natural and Constructed Wetlands in the Florida Everglades
AU: * Stern, J C
EM: stern@gly.fsu.edu
AF: Department of Geological Sciences, Florida State University/National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr. , Tallahassee, FL 32310 United States
AU: Wang, Y
EM: ywang@magnet.fsu.edu
AF: Department of Geological Sciences, Florida State University/National High Magnetic Field Laboratory, 1800 E. Paul Dirac Dr. , Tallahassee, FL 32310 United States
AU: Gu, B
EM: bgu@sfwmd.gov
AF: South Florida Water Management District, 3301 Gun Club Rd., West Palm Beach, FL 33406 United States
AB: Stable and radiocarbon isotopic contents of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) were used to examine the source and turnover rate of carbon in natural and constructed wetlands in the Florida Everglades. DOC concentrations decreased with decreasing phosphorus (P) concentrations along a water quality gradient from the agriculturally impacted areas in the northern Everglades to the more pristine Everglades National Park. $\delta$$^{13}$C values of DOC in the area reflect contributions of both wetland vegetation and sugarcane from agriculture. Radiocarbon ages of DOC, POC and DIC in the Everglades ranged from 2010 years BP to "$>$modern". The old $^{14}$C ages of DOC and POC were found in impacted areas near the Everglade Agricultural Area (EAA) in the northern Everglades. In contrast, DOC and POC in pristine marsh areas had near modern or "$>$modern" $^{14}$C ages. These data indicate that a major source of POC and DOC in impacted areas is the degradation of historic peat deposits in the EAA. In the pristine areas of the marsh, DOC represents a mix of modern and historic carbon sources, whereas POC comes from modern primary production as indicated by positive $\Delta$$^{14}$C values. High $\Delta$$^{14}$C values of DIC indicate that dissolution of limestone is not a significant source of DIC in the Everglades wetlands. A 68.5% turnover of DOC from the northern to the southern Everglades was estimated using radiocarbon data. Our study suggests that $\Delta$$^{14}$C measurements can be a useful indicator of the progress of ecosystem restoration in the Everglades. As a restored wetland moves towards its "original" or "natural" state, the $^{14}$C signatures of DOC should approach that of modern atmosphere. In addition, measurements of concentration and carbon isotopic composition of DOC in two small constructed wetland test cells indicate that these freshwater wetland systems contain a labile DOC pool with rapid turnover times and that the test cells are overall net sinks of DOC.
DE: 4806 Carbon cycling
DE: 4860 Radioactivity and radioisotopes
DE: 1040 Isotopic composition/chemistry
DE: 1045 Low-temperature geochemistry
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting