HR: 1340h
AN: B33A-0864    [Abstracts]
TI: Aerobic and Anaerobic Oxidation of Organic Acids in Yellowstone Hot Spring Ecosystems
AU: * Windman, T O
EM: beaker1@cox.net
AF: Arizona State University, Department of Chemistry and Biochemistry, Tempe, Az 85287- 1604,
AU: Zolotova, N
EM: nzolotova@asu.edu
AF: Arizona State University, Department of Earth and Space Exploration, Tempe, Az 85287- 1404,
AU: Shock, E
EM: eshock@asu.edu
AF: Arizona State University, Department of Chemistry and Biochemistry, Tempe, Az 85287- 1604,
AU: Shock, E
EM: eshock@asu.edu
AF: Arizona State University, Department of Earth and Space Exploration, Tempe, Az 85287- 1404,
AB: Thermodynamic analysis of energy supply based on samples collected from continental hot spring ecosystems at Yellowstone show that aerobic reactions yield the greatest energy. In terms of energy per mole of electrons transferred, aerobic oxidation of organic acids rivals or exceeds the energy supply from aerobic oxidation of hydrogen, CO, hydrogen sulfide, pyrite, sulfur or ammonia. This analysis is derived from samples collected where hot spring fluid are in contact with the atmosphere. It is likely that oxygen will be present at lower concentrations deeper in the system, which will place hard constraints on aerobic lifestyles. If so, which metabolisms could be supported deeper in the system? How will other oxidants be used to release energy? What characterizes the transition from aerobic to anaerobic oxidation? To answer these questions, pH, temperature, and alkalinity were measured in the field while measurements of dissolved oxygen and other redox-sensitive species (nitrate, ammonia, ferrous iron, and sulfide) were made with field-portable spectrophotometers and samples were taken for analysis of organic and inorganic ions by ion chromatography. Conditions in the subsurface can be predicted by starting from measured oxygen concentrations and calculating the effect of decreasing the concentration on the overall energetics of the system. Depending on hot spring composition, the amount of energy from aerobic oxidation of organic acid anions like succinate matches that from anaerobic oxidation (by nitrate or sulfate) once the log of the activity of dissolved oxygen drops to -6 to -8. These activities are 1 to 4 orders of magnitude lower that values determined for surface water in the hot springs. At lower oxygen activities aerobic oxidation gives way to anaerobic oxidation, and organic oxidation is more likely to involve nitrate and sulfate. Preliminary estimates indicate that these changes may occur at shallow depths in hot spring sediments (perhaps within the first centimeter), which suggests great differences between conditions inferred from fluids and those inferred from genomic data based on sediments or isolates from the same hot spring system.
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0456 Life in extreme environments
DE: 0466 Modeling
DE: 0471 Oxidation/reduction reactions (4851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting