HR: 17:45h
AN: B14A-07    [Abstracts]
TI: Microbial Diversity Under Long-Term Forcing by Acid-Mine Drainage and Metals Contamination in an Urban Wetland
AU: * Moreau, J W
EM: moreau@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Environmental Science, Policy and Management, University of California at Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767 United States
AB: Few microbial diversity studies have been performed of natural wetlands under long-term forcing by acid mine drainage (AMD) and metals. Sulfate-reducing bacteria (SRB) are ubiquitous in uncontaminated wetlands and can immobilize dissolved metals as metal-sulfides (e.g. Webb et al. 1998). Sulfide-oxidizing microbes, however, will promote the formation of sulfuric acid and the release of sorbed or precipitated metals to groundwater. Therefore, understanding the balance of sulfur-cycling and other microbes from source to sink along the contaminant gradient in a natural system under long-term contamination is of primary interest to bioremediation strategies involving the use of constructed wetlands. We previously reported on bacterial diversity in sediments of the contaminated Western Stege Marsh, at the Richmond Field Station along the eastern central San Francisco Bay. This marsh has been exposed to pH 2, metal-rich groundwaters from near-surface roasted pyrite-ore tailings for over a half-century prior to recent excavation and remediation. Sediment cores were collected using sterile sampling methods at sites with pH values from 2 to 8 along a horizontal contaminant gradient in a tidal slough. 16S rDNA clone libraries from each site reveal key differences in the structure of sulfur-cycling microbial communities between sediments sampled from a standing pond of acidic brackish waters (pH 2, 25 psu) to points along the tidal slough through which this acid communicated with SF Bay tides. New data show that the acid pond sulfur-oxidizing community, in addition to the dominant Bacterial species Thiomicrospira denitrificans, contains several Archaea most closely related to Thermoplasma and environmental clones from studies of coal-refuse contaminated wetlands. Sulfate-reducing bacteria remain dominant in the structure of slough sediment communities, and seem to be effective in reducing dissolved metals concentrations to below EPA maximum contaminant or action level standards. Interestingly, SRB are also significantly present (15%) and, based on sulfur isotopic studies, remain metabolically active in acidic sediments as well. This observation reflects the capacity for some SRB to remain metabolically active in the presence of low pH conditions generally thought to be highly unfavorable for their growth.
DE: 0418 Bioremediation
DE: 0448 Geomicrobiology
DE: 0488 Sulfur cycling
DE: 0493 Urban systems
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: Fall Meeting 2005