HR: 16:30h
AN: B42E-03    [PDF]
TI: Effects of Long-Term Acid-Mine Drainage Contamination on Diversity and Activity of Sulfate-Reducing Bacteria in a Natural Salt Marsh.
AU: * Moreau, J W
EM: moreau@eps.berkeley.edu
AF: Department of Earth and Planetary Science, University of California-Berkeley, 307 McCone Hall University of California-Berkeley, 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-Berkeley, 307 McCone Hall University of California-Berkeley, Berkeley, CA 94720-4767 United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Environmental Science, Policy and Management, 151 Hilgard Hall #3110 University of California-Berkeley, Berkeley, CA 94720-3110 United States
AB: Constructed wetlands have been studied as sites or analogs for {\it in situ} bioremediation of metal contaminants from acid mine drainage (AMD) or industrial sources (e.g. Webb et al. 1998). Wetlands bioremediation necessarily invokes the ubiquity and robustness of sulfate-reducing bacteria (SRB) to sequester dissolved metals into various poorly soluble metal-sulfides (e.g. PbS, CdS). However, few studies of natural wetlands under long-term ecological forcing by AMD or other contaminant sources are available for context. We are investigating the microbial diversity, mineralogy and geochemistry of a highly contaminated salt marsh along the East Central San Francisco Bay. For nearly a half-century, areas within this marsh have received acidic and/or metal-rich groundwaters from near-surface pyrite tailings (transported there from Iron Mountain Mine, near Redding, CA) and local industrial sources (e.g. paint and explosives manufacturers). Sediment cores (30-40 cm long) were taken from six contaminated sites in the marsh with pH range of $\sim$2 to $\sim$8. Previous analyses (URS Corp. 2001) reported As, Cd, Cu, Se, Zn, and Pb present in sediments at extremely high concentrations (100s of ppm), yet our ICP-AES analyses of pore waters showed only As present at concentrations of 10-50 ppb. We infer, from high-resolution transmission electron microscope (HRTEM) studies of biogenic (SRB biofilm) ZnS (Moreau et al. 2003, in review) and marsh sediments, that contaminant metals have been sequestered into aggregates of nanocrystalline metal-sulfides. Continuous-flow isotope ratio mass spectrometer (CF-IRMS) analyses of pore-water sulfate and sedimentary sulfides allow resolution of contributions to dissolved sulfate and sulfide from tailings oxidation and dissimilatory sulfate reduction. Sulfate analyses from subsections of three cores (pH 2-3, 6-7, 7-8, respectively) all yield $\delta$$^{34}$S values consistent with bacterial sulfate reduction. We note that all three cores also contain very fine-grained black muds that are distinguishable from coarser pyrite cinders, and exhibit a noticeably strong sulfide odor. Aero- and halo-tolerant SRB were enriched from circumneutral pH cores, and we hypothesize that acido-tolerant SRB may also be present. Analysis of restriction fragment length polymorphism of whole community 16S rDNA extracted from each core shows an expected increase in diversity between acidic and circumneutal sediments, and clone libraries from both contaminated and uncontaminated marsh sediments are being compared to assess the impact of long-term contamination. {\it References:} Webb et al. 1998, {\it J. Appl. Microbio., 84,} 240-248; Moreau et al. 2003, {\it Amer. Min.}, in review; URS Corp. 2001, {\it Report 51.09967067.00.}
DE: 0400 Biogeosciences
DE: 1040 Isotopic composition/chemistry
DE: 1890 Wetlands
DE: 3675 Sedimentary petrology
DE: 4840 Microbiology
SC: Biogeosciences [B]
MN: 2003 Fall Meeting