HR: 14:40h
AN: B53C-05    [Abstracts]
TI: Methane Consumption in Marine Waters Impacted by Gas Seepage
AU: * Heintz, M B
EM: mbheintz@umail.ucsb.edu
AF: University of California Santa Barbara, Earth Science Department, Webb Hall, Santa Barbara, CA 93106, United States
AU: Mau, S
EM: mau@geol.ucsb.edu
AF: University of California Santa Barbara, Earth Science Department, Webb Hall, Santa Barbara, CA 93106, United States
AU: Valentine, D L
EM: valentine@geol.ucsb.edu
AF: University of California Santa Barbara, Earth Science Department, Webb Hall, Santa Barbara, CA 93106, United States
AU: Yang, J
EM: jinshu@interchange.ubc.ca
AF: University of British Columbia, Department of Mirobiology and Immunology, Vancouver, BC V6T 1Z3, Canada
AU: Hallam, S J
EM: shallam@interchange.ubc.ca
AF: University of British Columbia, Department of Mirobiology and Immunology, Vancouver, BC V6T 1Z3, Canada
AU: Reed, J H
EM: wortstellung@yahoo.com
AF: University of California Santa Barbara, Earth Science Department, Webb Hall, Santa Barbara, CA 93106, United States
AB: Microbially mediated methane oxidation in the coastal marine water column is an important sink term in the global methane budget, but remains a relatively uncharacterized process. While oxidation in the water column prevents up to two-thirds of methane released from the sea-floor from transiting to the atmosphere, only a limited number of oxidation rates have been measured, and identities of the microorganisms responsible for methane consumption in this environment remain unknown. To date, there have been no comprehensive studies on the relationship between methane oxidation rates and the microbial population responsible for methane oxidation. As a result of the perennially elevated methane concentrations in the water column at cold seeps, these environments are ideal for investigating the composition and efficacy of pelagic marine methane oxidizing communities. A suite of filter samples were collected, and corresponding methane concentrations and oxidation rates measured, in a series of vertical hydrocasts at seep and background sites in the Santa Barbara and Santa Monica Basins during the SEEPS'07 cruise. Here we present data from samples collected in a grid through the methane plume emanating from the Coal Oil Point (COP) seep field in the Santa Barbara Basin, and from a series of vertical casts above a mud volcano in the Santa Monica Basin. Methane oxidation rate measurements were made using a 3H-CH4 tracer. Preliminary calculations of fractional turnover rates in the water column down- current from the COP seep field indicate a maximum fractional turnover rate of 0.04 day-1 at 50-70 m depth, approximately 25 km from the seep field, along the path of plume advection. In the Santa Monica Basin, fractional turnover rates are highest at the bottom (0.03 day-1 at 800 m), decrease to a minimum (0.002 day-1) at 600 m, and increase from 0.003 day-1 at 300 m to 0.009 day-1 at 25 m. Current molecular work will be presented, and is focused on identifying methanotrophic bacteria based on both functional (pmoA) and phylogenetic (16S rDNA) genes, and on comparing community composition across gradients in methane concentration and oxidation rate, and between seepage sites.
DE: 0428 Carbon cycling (4806)
DE: 0460 Marine systems (4800)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting