HR: 17:00h
AN: C54A-05 INVITED    [Abstracts]
TI: Microbial Energetics Beneath the Taylor Glacier, Antarctica
AU: * Mikucki, J A
EM: jmikucki@fas.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, Camridge, MA 02138, United States
AU: Turchyn, A V
EM: avturchyn@berkeley.edu
AF: Department of Earth and Planetary Sciences, UC Berkeley, Berkeley, CA 94720, United States
AU: Farquhar, J
EM: jfarquha@essic.umd.edu
AF: Department of Geology, University of Maryland, College Park, MD 20742, United States
AU: Priscu, J C
EM: jpriscu@montana.edu
AF: Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, United States
AU: Schrag, D P
EM: daniel_schrag@harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, Camridge, MA 02138, United States
AU: Pearson, A
EM: pearson@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, Camridge, MA 02138, United States
AB: Subglacial microbiology is controlled by glacier hydrology, bedrock lithology, and the preglacial ecosystem. These factors can all affect metabolic function by influencing electron acceptor and donor availability in the subglacial setting leaving biogeochemical signatures that can be used to determine ecosystem processes. Blood Falls, an iron-rich, episodic subglacial outflow from the Taylor Glacier in the McMurdo Dry Valleys Antarctica provides an example of how microbial community structure and function can provide insight into subglacial hydrology. This subglacial outflow contains cryoconcentrated, Pliocene-age seawater salts that pooled in the upper Taylor Valley and was subsequently covered by the advance of the Taylor Glacier. Biogeochemical measurements, culture-based techniques, and genomic analysis were used to characterize microbes and chemistry associated with the subglacial outflow. The isotopic composition of important geochemical substrates (i.e., δ³⁴S_sulfate, Δ³³S_sulfate, δ¹⁸O_sulfate, δ¹⁸O_water, Δ¹⁴S_DIC) were also measured to provide more detail on subglacial microbial energetics. Typically, subglacial systems, when driven to anoxia by the hydrolysis of organic matter, will follow a continuum of redox chemistries utilizing electron acceptors with decreasing reduction potential (e.g., Fe (III), sulfate, CO₂). Our data provide no evidence for sulfate reduction below the Taylor Glacier despite high dissolved organic carbon (450 μM C) and measurable metabolic activity. We contend that, in the case of the Taylor Glacier, the in situ bioenergetic reduction potential has been ‘short-circuited' at Fe(III)-reduction and excludes sulfate reduction and methanogenesis. Given the length of time that this marine system has been isolated from phototrophic production (~2 Mya) the ability to degrade and consume increasingly recalcitrant organic carbon is likely an important component to the observed redox chemistry. Our work indicates that glacier hydrology imparts strong feedbacks on the availability of oxygen as an electron acceptor and may be a robust regulator of the in situ metabolism. This biogeochemical regulation in turn affects the chemical nature of subglacial efflux. Blood Falls demonstrates that measurements of geochemistry and microbial diversity can support models of subglacial hydrology.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0716 Cryobiology (0475)
DE: 0720 Glaciers
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
SC: Cryosphere [C]
MN: 2007 Fall Meeting