HR: 14:45h
AN: B23C-05    [Abstracts]
TI: A Habitat for Living Microbes on Silt Grains in Greenland Basal Ice at 3053m Depth
AU: * Tung, H C
EM: ctung@berkeley.edu
AF: Department of Environmental Science, Policy and Management, 328 Birge Hall, University of California, Berkeley, CA 94720 United States
AU: Bramall, N
EM: bramall@socrates.berkeley.edu
AF: Department of Physics, 151 LeConte Hall, University of California, Berkeley, CA 94720 United States
AU: Price, P
EM: bprice@berkeley.edu
AF: Department of Physics, 151 LeConte Hall, University of California, Berkeley, CA 94720 United States
AB: Two ice cores 30 km apart extended ~3050 m down to bedrock at Summit, Greenland. Most attention has been focused on their high-resolution climate record covering the last $\sim$110,000 years. In the bottom few meters, we measured up to $\sim$1 wt% of silt (mean diameter 2.5$\mu$m). In that basal ice of GRIP, R. Souchez et al. found a factor of 500 excess of CO$_{2}$ and a factor of $10^4$ excess of CH$_{4}$, and T. Sowers measured a factor 2 $\times 10^4$ excess of CH$_{4}$ at 3043 m in the nearby GISP2 basal ice. V. Miteva et al. discovered $\sim$7 $\times 10^7$ microbial cells/ml in Sowers\'sample. Souchez et al. inferred from the huge excesses that the ice formed by mixing with a peat deposit. It is now inferred from our work and the observations of Miteva et al. that the excesses were the direct products of in-situ microbial metabolism. The basal ice, with its silt and microbial population, likely formed before the ice sheet developed. Using various stains and epifluorescence, we analyzed the relationships of microbes to silt grains at six depths from 3044 to 3053 m in GISP2 ice as well as the climate correlation with microbes along throughout the entire ice core. In the silty ice, microbial concentrations ranged from $\sim$ 10^7$ to $>10^9$/cm$^{3}$ of ice and correlated with weight fraction of silt rather than with depth. Between 92% and 99% of the microbes were attached to silt particles at a typical concentration of $\sim10^7$/cm$^{2}$ of grain surface. This correlation extended down to the smallest silt grains: typically, up to 4 cells were attached to a 0.5$\mu$m grain. With an SEM we found that some cells were dividing, and we were able to culture microbes in low-nutrient liquid media. These two results demonstrated their viability after $10^5$ yr at -9$\deg$C.
DE: 4840 Microbiology
DE: 6020 Ice
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting