HR: 1340h
AN: B33B-0257    [Abstracts]
TI: Microbial Distributions Through Pore Water Geochemical Gradients: How Well do Contemporary Organism Genomes Track Their Environment?
AU: * Berelson, W
EM: berelson@usc.edu
AF: Department Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740 United States
AU: Prokopenko, M
EM: prokopen@usc.edu
AF: Department Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740 United States
AU: Stevenson, B
EM: steven77@msu.edu
AF: Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824 United States
AU: Spear, J
EM: John.Spear@colorado.edu
AF: Biology Department, University of Colorado, Boulder, CO 80309 United States
AU: Dawson, S
EM: sdawson@nature.berkeley.edu
AF: MCB Department, University of California, Berkeley, CA 94720 United States
AU: Hugenholtz, P
EM: phugenholtz@lbl.gov
AF: DOE JGI, 2800 Mitchell Drive Bldg 400-404, Walnut Creek, CA 94598 United States
AU: Class, G
EM: close@usc.edu
AF: USC Wrigley Institute, University of Southern California, Los Angeles, CA 90089-0371 United States
AB: In order to better understand a marine sediment ecosystem, we have measured pore water profiles and microbial community structure through the upper 30 cm of laminated muds collected from 900 m water depth in San Pedro Basin The sediments at this site are hemipelagic, derived from erosion from the Southern California land mass and from biogenic production in the San Pedro Channel water column. These sediments accumulate at a rate of 0.25 mm/year under a water column which has <20 uM oxygen, hence the sediments are not bioturbated. Under these conditions, a biogeochemical zonation should develop with respect to oxidant supply and reactant production. Oxygen is absent within pore waters below 0.5 mm. Nitrate concentration is unusual, peaking at 50-100 uM at depths of 2-5 cm-we suspect that nitrate is injected into these sediments through the microbial community, as diffusion-reaction models cannot explain this nitrate maximum. Although ammonium concentrations increase monotonically with depth, the profile of ammonium 15N values show isotopic enrichment of about 3 to 4 % at 6 -15 cm, relative to the values directly below and above. This enrichment suggests ammonium oxidation occurring at this depth. Hence, within a range of 15 cm of a `simple' hemipelagic sediment column, the biogeochemical variability is extraordinary. Within this context we have used molecular tools to compare the microbial community structure with the biogeochemical structure and identified the abundant members of this community. As molecular tools will be applied to address questions about paleoenvironments and earth history, we stress the importance of understanding complexities within modern sediments.
DE: 4804 Benthic processes/benthos
DE: 4840 Microbiology
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting