HR: 0830h
AN: B51C-0981    [PDF]
TI: Environmental Influences on Microbial Mat Community Structure and Mineralization.
AU: * Prufert-Bebout, L E
EM: Leslie.E.Bebout@nasa.gov
AF: NASA Ames Research Center, Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000
AU: Carpenter, S
EM: scarpenter@mail.arc.nasa.gov
AF: Enterprise Advisory Services Inc, c/o Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000 United States
AU: Cote, T
EM: tcote@mail.arc.nasa.gov
AF: Foothill-DeAnza Internship Program, c/o Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000 United States
AU: Clark, T
EM: tclark@mail.arc.nasa.gov
AF: Foothill-DeAnza Internship Program, c/o Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000 United States
AU: Hogan, M
EM: mhogan@mail.arc.nasa.gov
AF: NASA Ames Research Center, Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000
AU: Moreau, J
EM: moreau@eps.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone Hall University of California, Berkeley, Berkeley, CA 94035-1000 United States
AU: Orphan, V
EM: vorphan@mail.arc.nasa.gov
AF: National Research Council postdoctoral program), c/o Exobiology Branch Mailstop 239-4, Moffett Field, CA 94035-1000 United States
AB: Microbial mats consist of complex microbial communities containing of thousands of phylotypes of microorganisms living in close proximity to one another. These communities frequently thrive at the interface between benthic sediment substrate and overlying water. The microbial community draws nutrients from the environment and releases metabolic waste products which may in turn; serve as substrates for other microbial groups, be exchanged with the bulk environment (sediment or water column), or precipitate into mineral phases. Gross environmental changes, such as nutrient availability, irradiance level, hydrodynamic flow regime, temperature or water chemistry can directly affect the balance between these processes, in turn affecting microbial community and mineral distribution. We will present a brief survey of visually observable community distribution responses in natural microbial mats to controlled shifts in ecosystem incubation conditions. A more detailed examination of significant population shifts in three important microbial mat groups; cyanobacteria, sulfate reducing bacteria and methanogens, using a combination of visualization and molecular methods, in response to manipulation of ambient environmental sulfate levels will be presented. Lowering of sulfate to levels inhibiting sulfate reduction yielded an increase in methane production (see B. Bebout et al., session U09), and resulted in production of a discrete mineralizing layer within the mat running below, but parallel to the mat surface. Multiple zone-axes electron diffraction patterns and energy-dispersive X-ray spectroscopy were used to unambiguously identify the phase as aragonite. Implications of this incipient mineral phase as a possible precursor to carbonate mineralization in a previously non-mineralizing microbial mat system will be discussed in the context of interacting effects of the sulfate water chemistry change on community composition and rate process changes within the mat.
DE: 0400 Biogeosciences
DE: 3630 Experimental mineralogy and petrology
DE: 4825 Geochemistry
DE: 4840 Microbiology
SC: Biogeosciences [B]
MN: 2003 Fall Meeting