HR: 16:30h
AN: OS52D-03    [PDF]
TI: Biogeochemical Investigations of Methane Seepage, Hydrate Ridge, OR.
AU: * Valentine, D L
EM: valentine@geol.ucsb.edu
AF: University of California, Department of Geological Sciences, Santa Barbara, CA 93106
AU: Solem, R C
EM: rsolem@ucsd.edu
AF: Scripps Institution of Oceanography, University of California 9500 Gilman Drive-0202, San Diego, CA 92093
AU: Kastner, M
EM: mkastner@ucsd.edu
AF: Scripps Institution of Oceanography, University of California 9500 Gilman Drive-0202, San Diego, CA 92093
AU: Wardlaw, G D
EM: gwardlaw@umail.ucsb.edu
AF: University of California, Department of Geological Sciences, Santa Barbara, CA 93106
AU: Boone, D R
EM: booned@pdx.edu
AF: Portland State Univerisity, Department of Biological Sciences, Portland, OR 97207
AU: Kendall, M
EM: kendallm@pdx.edu
AF: Portland State Univerisity, Department of Biological Sciences, Portland, OR 97207
AU: Wang, X
EM: Xuchen.Wang@umb.edu
AF: University of Massachusets, 100 Morrissey Blvd., Boston, MA 02125
AU: Hill, T M
EM: tessa@umail.ucsb.edu
AF: University of California, Department of Geological Sciences, Santa Barbara, CA 93106
AU: Purdy, A
EM: apurdy@ucsd.edu
AF: Scripps Institution of Oceanography, University of California 9500 Gilman Drive-0202, San Diego, CA 92093
AU: Bartlett, D H
EM: dbartlett@ucsd.edu
AF: Scripps Institution of Oceanography, University of California 9500 Gilman Drive-0202, San Diego, CA 92093
AB: During July, 2002 we conducted a series of biogeochemical studies at the southern summit of Hydrate Ridge, OR. Using the DSV Alvin we collected sediment push cores from 2 distinct types of seep environments (clam beds and microbial mats) and from control sites (bare sediment). Samples from each setting were analyzed for the depth distributions of microbial abundance, most probable number counts for methanogenic archaea, volatile organic acids, dissolved organic carbon (including $\delta$$^1$$^3$C), total organic carbon (including $\delta$$^1$$^3$C and $\Delta$$^1$$^4$C), sulfate, alkalinity (including $\delta$$^1$$^3$C-DIC), $\delta$$^1$$^3$C-CH$_4$, as well as the distribution of bacterial and archaeal 16S rDNA genes. These distributions provide the basis for a comparative analysis of the distinct seep environments and of biogeochemical controls on methane hydrate. Primary production in the seeps appears to be driven by anaerobic methane oxidation in the sediments and sulfide oxidation at the sediment-water interface. However, results indicate distinctive microbial habitats in the different seep settings. Results further indicate a vigorous, secondary microbial community living off the wastes of the primary producers. High levels (up to 4%) of $^1$$^3$C-depleted ($\sim$-45$\permil$) organic carbon in the seeps and high C:N ratios (as high as 50:1) indicate a buildup of CH$_4$-derived organic carbon, and raise the possibility of nitrogen limitation impacting seep communities.
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
DE: 1050 Marine geochemistry (4835, 4850)
DE: 4803 Bacteria
DE: 4805 Biogeochemical cycles (1615)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting