HR: 1340h
AN: B43A-0898    [Abstracts]
TI: Environmental controls on methanogen viability in the hydrothermal waters of the El Tatio geyser field, Chile.
AU: * Franks, M A
EM: MeganFranks@mail.utexas.edu
AF: University of Texas at Austin, Jackson School of Geosciences, 1 University Station Mail Stop C-1100, Austin, TX 78712, United States
AU: Bennett, P C
EM: pbennett@mail.utexas.edu
AF: University of Texas at Austin, Jackson School of Geosciences, 1 University Station Mail Stop C-1100, Austin, TX 78712, United States
AU: Omelon, C
EM: omelon@mail.utexas.edu
AF: University of Texas at Austin, Jackson School of Geosciences, 1 University Station Mail Stop C-1100, Austin, TX 78712, United States
AU: Engel, A S
EM: aengel@geol.lsu.edu
AF: Louisiana State University, Department of Geology and Geophysics, Howe-Russell Geoscience Complex, Baton Rouge, LA 70803, United States
AB: At the El Tatio geyser field, a unique hydrothermal site located in the Andes Mountains in Chile, methanogenic archaea were found in only two of the hundreds of hydrothermal features. Reported here is an investigation into the environmental and geochemical controls on the distribution of methanogenic archaea. Located in the hyper- arid Atacama Desert, El Tatio waters are characterized by high salinity (95-175mM), Na-Cl type waters and circum-neutral pH (6.5-7), with very low inorganic carbon (0.1-0.5 mM TIC), but very high concentrations of As and Sb (300-700 uM As, 10-30uM Sb). Extensive bacterial mats thrive in most of the shallow run-off streams originating from hydrothermal features. In order to determine geochemical controls on methanogen populations, major and trace elements, including As and Sb speciation and concentrations, were determined using IC and HPLC-ICP-MS methods. The structure of microbial communities was analyzed using MPN enumeration of methanogens, culturing, and phylogenetic analysis using molecular techniques. Here, as in many hydrothermal regions, temperature and geochemical gradients influence the microbial ecology. Results from MPN enumeration indicate methanogen populations are dominated by H2-utilizing (carbonate reducing) archaea at both of the sites, with some acetate-oxidizing archaea present. These sites contain comparatively high DIC concentrations; however, it is unclear whether this is a control or a product of methanogenic archaea. Water quality analyses also show a strong correlation between antimony concentrations and the presence of methanogens; methanogenic archaea being present only at sites with 17 uM Sb concentrations or less.
DE: 0410 Biodiversity
DE: 0448 Geomicrobiology
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting