HR: 0800h
AN: B21B-0888    [Abstracts]
TI: Dissolved Free Amino Acids in Hydrothermal Springs at Yellowstone National Park, U.S.A.
AU: * Cox, J S
EM: JCox@asu.edu
AF: Arizona State University, Dept. Geological Sciences, P.O. Box 871404, Tempe, AZ 85287-1404 United States
AU: Holland, M E
EM: Melanie.Holland@asu.edu
AF: Arizona State University, Dept. Geological Sciences, P.O. Box 871404, Tempe, AZ 85287-1404 United States
AU: Shock, E L
EM: eshock@asu.edu
AF: Arizona State University, Dept. Geological Sciences, P.O. Box 871404, Tempe, AZ 85287-1404 United States
AB: Insights into the organic geochemistry of hydrothermal systems, as well as the dynamics of biotic processes in hot spring ecosystems, can be gained by identifying and quantifying dissolved free amino acids (DFAA). Hydrothermal systems form a unique environmental subset relative to other aqueous settings due to their higher temperatures, largely uncharacterized and exotic microbiology, wider pH range, and elevated levels of rare metals, sulfur, and dissolved gases. Previous studies of hot spring and geothermal systems (e.g. Mukhin et al., 1979; Svensson et al., 2004) indicated the presence of micromolar quantities of various amino acids, but the underlying mechanisms controlling amino acid production and disappearance/consumption have continued to remain elusive. DFAA were identified and quantified in five hot springs at Yellowstone National Park that span a range of pH (2 to 8) and temperature (75 to 93$\deg$C/boiling). Biotic uptake experiments and enantiomeric analyses on samples from one location were also performed to elucidate biotic pathways. Analyses were performed using high pressure anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), which is able to resolve amino acids as well as certain carbohydrates, oligopeptides, and a variety of related biological molecules. Preliminary data indicate that total DFAA concentrations are quite low (sub-micromolar range) and that amino acids with aliphatic and nitrogen-containing R-groups are predominant in the DFAA fraction. The types and concentrations of amino acids were variable across the sites. Obsidian Pool (pH 5.1, 77.5$\deg$C), where multiple microbiological studies have been conducted, was found to have a DFAA fraction consisting primarily of glycine with trace amounts of arginine, lysine, and histidine. In comparison, an acidic spring in the Sylvan Springs area (pH 1.9, 79.7$\deg$C) had higher total DFAA concentrations and was found to contain primarily arginine, lysine, and leucine, together with trace amounts of alanine, proline, and histidine. At least six other unknown compounds were also observed, one of them possibly at near-micromolar levels, and there was evidence for higher levels of organic compounds in general. The generally low concentrations observed in this study suggest that amino acids participate in highly dynamic biotic pathways in Yellowstone hot springs. Our observations of lower concentrations of amino acids and less diversity differ from literature results, but are consistent with suggestions of a positive correlation between acidic conditions and higher levels of DFAA (Svensson et al., 2004). References: Mukhin L.M., Bondarev V.B., Vakin E.A., Il'yukhina N.I., Kalinichenko V.I., Milekhina E.I., Safonova E.N. (1979) Doklady Akademii Nauk SSSR 244(4), 974-7. Svensson E., Skoog A., and Amend J.P. (2004) Organic Geochemistry 35, 1001-1014.
UR: http://geopig.asu.edu
DE: 8424 Hydrothermal systems (8135)
DE: 4805 Biogeochemical cycles (1615)
DE: 1055 Organic geochemistry
DE: 0400 Biogeosciences
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting