HR: 1340h
AN: B13C-0253    [Abstracts]
TI: Fatty Acids in Tubeworm-Associated Sediments in the Gulf of Mexico
AU: * Nielson, K E
EM: knielson@geosc.psu.edu
AF: Department of Geosciences, 303 Deike Building The Pennsylvania State University, University Park, Pa 16802 United States
AU: Gilhooly, W P
EM: wpg6n@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904 United States
AU: Sati, S
EM: shalinisati@yahoo.com
AF: Department of Geosciences, 303 Deike Building The Pennsylvania State University, University Park, Pa 16802 United States
AU: Macko, S A
EM: sam8f@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904 United States
AU: Fisher, C R
EM: cfisher@psu.edu
AF: Department of Biology, The Pennsylvania State University, University Park, PA 16802 United States
AU: Freeman, K H
EM: kate@essc.psu.edu
AF: Department of Geosciences, 303 Deike Building The Pennsylvania State University, University Park, Pa 16802 United States
AB: Vestimentiferan tubeworms in the Gulf of Mexico are a visible and unique component of the macrofaunal community. Tubeworm distribution is controlled by microbially produced sulfide. Sulfide is absorbed by tubeworms from sediments through posterior extensions of their bodies, euphemistically called "roots." Diffusion of seawater sulfate into the sediments may, on its own, provide insufficient sulfate for sulfate-reducing bacteria to supply the sulfide required by a large, mature tubeworm aggregation. Tubeworms potentially overcome this shortfall by actively facilitating sulfate migration into anoxic sediments, possibly by excreting sulfate through their roots. Microbial biomass production would be stimulated by increased sulfate availability. In the summer of 2000, ten push cores were collected in close proximity to tubeworm aggregations using the submersible Johnson Sea-Link. Pore waters were analyzed for sulfur stable isotopes, and fatty acids from residual sediments were used to characterize the sediment microbial community. Lipid analysis shows a quantitive correlation between known bacterial biomarkers and the general biomass markers, hexadecanoate (16:0) and tetradecanoate (14:0). This correlation suggests that the extracted material is largely bacterial. Additionally, good correlations between biomarkers for sulfate-reducing bacteria, 13-methyltetradecanoate (ai-15:0) and 15-methylhexadecanoate (i-17:0), with hexadecanoate suggests microbial community composition does not change with respect to proximity of the tubeworm aggregation. Finally, microbial activity is largely controlled by labile organic matter inputs. Lipid distributions do not suggest tubeworms irrigate sediments with sulfate; however, this may be indicative of the small scale of sulfate diffusion from tubeworm roots rather than an absence of irrigation.
DE: 4805 Biogeochemical cycles (1615)
DE: 4830 Higher marine organisms
DE: 4850 Organic marine chemistry
DE: 4870 Stable isotopes
DE: 4803 Bacteria
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting