HR: 16:00h
AN: H44A-03    [Abstracts]
TI: Linking Food Webs and Biogeochemical Processes in Wetlands: Insights From Sulfur Isotopes
AU: * Stricker, C A
EM: cstricker@usgs.gov
AF: US Geological Survey, Denver Federal Center, Denver, CO 80225 United States
AU: Guntenspergen, G R
EM: glenn guntenspergen@usgs.gov
AF: US Geological Survey, Patuxent Wildlife Research Center, Laurel, MD 20706 United States
AU: Rye, R O
EM: rrye@usgs.gov
AF: US Geological Survey, Denver Federal Center, Denver, CO 80225 United States
AB: To better understand the transfer of nutrients into prairie wetland food webs we have investigated the cycling of S (via S isotope systematics and geochemistry) in a prairie wetland landscape by characterizing sources (ground water, interstitial water, surface water) and processes in a small catchment comprised of four wetlands in eastern South Dakota. We focused on S to derive process information that is not generally available from carbon isotopes alone. The wetlands chosen for study spanned a considerable range in SO₄ concentration (0.1-13.6 mM), which corresponded with landscape position. Ground water δ³⁴S_SO4 values remained relatively constant (mean = -13.2 per mil) through time. However, δ³⁴S_SO4 values of wetland surface waters ranged from -2.9 to -30.0 per mil (CDT) and were negatively correlated with SO₄ concentrations (p<0.05). The isotopic variability of surface water SO₄ resulted from mixing with re-oxidized sulfides associated with recently flushed wetland soils. The δ³⁴S signatures of wetland primary (Gastropoda: Stagnicola elodes) and secondary (Odonata: Anax sp.) consumers were significantly related to surface water δ³⁴S_SO4 values (p<0.05) suggesting that food web components were responding to changes in the isotopic composition of the S source. Both primary and secondary consumer δ³⁴S signatures differed between wetlands (ANOVA, p<0.05). These data illustrate the complexity of S cycling in prairie wetlands and the influence of wetland hydrologic and biogeochemical processes on prairie wetland food webs. Additionally, this work has demonstrated that sulfur isotopes can provide unique source and process information that cannot be derived from traditional carbon and nitrogen isotope studies.
DE: 1040 Isotopic composition/chemistry
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
DE: 1890 Wetlands
DE: 4805 Biogeochemical cycles (1615)
SC: Hydrology [H]
MN: 2005 Joint Assembly