HR: 0800h
AN: B11A-1021    [Abstracts]
TI: Comparison of Bulk and Compound-Specific Carbon Isotope Analyses and Determination of Carbon Sources to Salt Marsh Sediments Using n-Alkane Distributions (Maine, USA)
AU: * Tanner, B R
EM: btanner@wcu.edu
AF: Dept. of Geosciences and NRM, Western Carolina University , 349 Stillwell Bldg., Cullowhee, NC 28723 United States
AU: Uhle, M E
EM: muhle@nas.edu
AF: Polar Research Board, The National Academies, 500 Fifth St. NW , Washington, DC 20001 United States
AU: Kelley, J T
EM: jtkelley@maine.edu
AF: Dept. of Earth Sciences, University of Maine, Bryand Global Sciences Center, Orono, ME 04469 United States
AU: Mora, C I
EM: cmora@utk.edu
AF: Dept. of Earth and Planetary Sciences, University of Tennessee, EPS Bldg., Knoxville, TN 37996 United States
AB: Sources of sedimentary organic matter to a Morse River, Maine (USA) salt marsh over the last 3390+/-60 RCYBP are determined using distribution patterns of n-alkanes as well as bulk and compound-specific carbon isotopic analysis. Marsh foraminiferal counts indicate the ubiquitous presence of zone 1B deposits, suggesting that the deposits were laid down ~0.2 to 0.5m above mean high water. Distributions of n-alkanes show a primary contribution from higher plants, confirmed by an average ACL value of 27.5 for the core sediments and CPI values above 3. Many sample depths have a maximum abundance at the C25 alkane. Ten low marsh, high marsh, and higher-high marsh plant species common to Maine salt marshes were sampled, including Spartina alterniflora, Spartina patens, Juncus gerardi and Solidago sempervirens. The ACL value for the average of the 10 marsh species is 29.1. Salicornia europa, usually not considered to be a dominant species in Maine marshes, has a similar n-alkane distribution to many of the salt marsh sediments, suggesting that it is an important source to the biomass of the marsh through time. Bacterial degradation or algal inputs to the marsh sediments appear to be minor. Compound specific carbon isotopic analyses of the C27 alkanes are, on average, 7.2ppt. depleted relative to bulk values, but the two records are strongly correlated (R2 = 0.87), suggesting that marsh plants are "swamping" the bulk carbon isotopic signal. The apparent abundance of a subordinate (though common) salt marsh plant species (Salicornia europa) within our core underscores the importance of using caution when applying mixing models of relatively few plant species to marsh sediments.
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0460 Marine systems (4800)
DE: 0476 Plant ecology (1851)
DE: 1041 Stable isotope geochemistry (0454, 4870)
SC: Biogeosciences [B]
MN: Fall Meeting 2005