HR: 0800h
AN: OS41D-0516    [Abstracts]
TI: A Lipid Molecular Marker Assessment of Sediments from the Northern Gulf of Mexico before and after the Passage of Hurricane Lili
AU: * Mead, R N
EM: rmead@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 700 Sumter Street , Columbia, SC 29208 United States
AU: Goni, M A
EM: goni@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 700 Sumter Street , Columbia, SC 29208 United States
AB: A lipid molecular marker (hydrocarbons, sterols and fatty acid) characterization was undertaken to identify the sources of organic matter to surface sediments from the Louisiana Shelf, west of the Atchafalaya River before and after the passage of Hurricane Lili. The data obtained point to relatively small changes in source with no large pulse of terrestrial materials following the passage of this category 2 hurricane. During both sampling periods, the terrestrial/aquatic ratios (TAR) estimated from the hydrocarbon compositions of surface sediments were consistently high (increased terrestrial component) at the near-shore sites while smaller TAR values (decreased terrestrial component) were observed at the offshore sites. All samples displayed unresolved complex mixtures (UCM), which ranged in concentration from 54.9 ŸYg/g OC to 426.5 ŸYg/g OC. Generally; the UCM concentrations were highest at the near-shore sites and decreased by an order of magnitude at the offshore sites. Sterols, linear, mono-and poly-unsaturated fatty acids from multiple organic matter sources were also detected at each site. Overall, these compounds are consistent with similar sources (higher plant, phytoplankton, zooplankton, diatom and bacterial) of organic matter albeit small differences between the pre- and post-hurricane samples were observed. Principle component analysis of the lipid concentration data revealed subtle differences in the distribution of organic matter sources among the samples. The pre-hurricane samples were characterized by lipid contributions from a mixture of higher plant, zooplankton, diatom and dinoflagellate sources while the post-hurricane samples were characterized by lipid contributions from higher plant, zooplankton and dinoflagellate sources, with little or no contributions from diatoms. The apparent difference between sampling cruises was not detected in the simple autochthonous/allochthonous molecular marker ratios or in other less specific molecular markers.
DE: 4825 Geochemistry
DE: 1055 Organic geochemistry
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting