TY - JOUR
T1 - Quantifying inorganic sources of geochemical energy in hydrothermal ecosystems, Yellowstone National Park, USA
AU - Shock, Everett
AU - Holland, Melanie
AU - Meyer-Dombard, D'Arcy
AU - Amend, Jan P.
AU - Osburn, G. R.
AU - Fischer, Tobias P.
N1 - Funding Information:
Thanks to those who helped with the field work resulting in the data presented here including: Maggie Osburn, Rachel Lindvall, Mitch Schulte, Karyn Rogers, Sarah Strauss, Panjai Prapaipong, Bill Winston, Barb Winston, Mike Singleton, Martine Simoes, Samantha Fernandes, Colin Enssle, and Andrew Dombard. Ion chromatography was supervised by Natalya Zolotova. Many entertaining and enlightening conversations with Tom McCollom, Roger Summons, Alex Bradley, Todd Windman, Jeff Havig, Alysia Cox, Hilairy Hartnett, Ariel Anbar and Eileen Dunn in the field and/or in the lab have contributed to this research effort. Thanks to Sue Selkirk for preparing our digitized maps for publication. This research would not be possible without the outstanding efforts of the US National Park Service and the dedicated staff of the Research Office at Yellowstone National Park who permitted us to work in the park. Thanks to Stefán Arnórsson and Wolfgang Bach for helpful reviews of the paper. Funding from the National Science Foundation ( OCE-9817730 ) and the NASA Astrobiology Institute (Carnegie subcontract 8210-14568-15 ) supported the field aspects of this research. Theoretical modeling was supported with funds from National Science Foundation Grant ( EAR-0525561 ) and NASA Exobiology and Evolutionary Biology Grant ( NNG05GQ67G ). E.S. dedicates this paper to the memory of his parents who introduced him to Yellowstone as a six-year-old, and to that of Harold Helgeson who continued to inspire into his 76th year.
PY - 2010/7
Y1 - 2010/7
N2 - Combining analytical data from hot spring samples with thermodynamic calculations permits a quantitative assessment of the availability and ranking of various potential sources of inorganic chemical energy that may support microbial life in hydrothermal ecosystems. Yellowstone hot springs of diverse geochemical composition, ranging in pH from <2 to >9 were chosen for this study, and dozens of samples were collected during three field seasons. Field measurements of dissolved oxygen, nitrate, nitrite, total ammonia, total sulfide, alkalinity, and ferrous iron were combined with laboratory analyses of sulfate and other major ions from water samples, and carbon dioxide, hydrogen, methane, and carbon monoxide in gas samples to evaluate activity products for ~300 coupled oxidation-reduction reactions. Comparison of activity products and independently calculated equilibrium constants leads to values of the chemical affinity for each of the reactions, which quantifies how far each reaction is from equilibrium. Affinities, in turn, show systematic behavior that is independent of temperature but can be correlated with pH of the hot springs as a proxy for the full spectrum of geochemical variability. Many affinities are slightly to somewhat dependent on pH, while others are dramatically influenced by changes in chemical composition. All reactions involving dissolved oxygen as the electron acceptor are potential energy sources in all hot spring samples collected, but the ranking of dominant electron donors changes from ferrous iron, and sulfur at high pH to carbon monoxide, hydrogen, and magnetite as pH decreases. There is a general trend of decreasing energy yields depending on electron acceptors that follows the sequence: O2(aq)>NO3-≈NO2-≈S>pyrite≈SO4-2≈CO(g)≈CO2(g) at high pH, and O2(aq)≈magnetite>hematite≈goethite>NO3-≈NO2-≈S≈pyrite≈SO4-2 at low pH. Many reactions that are favorable sources of chemical energy at one set of geochemical conditions fail to provide energy at other conditions, and vice versa. This results in energy profiles supplied by geochemical processes that provide fundamentally different foundations for chemotrophic microbial communities as composition changes.
AB - Combining analytical data from hot spring samples with thermodynamic calculations permits a quantitative assessment of the availability and ranking of various potential sources of inorganic chemical energy that may support microbial life in hydrothermal ecosystems. Yellowstone hot springs of diverse geochemical composition, ranging in pH from <2 to >9 were chosen for this study, and dozens of samples were collected during three field seasons. Field measurements of dissolved oxygen, nitrate, nitrite, total ammonia, total sulfide, alkalinity, and ferrous iron were combined with laboratory analyses of sulfate and other major ions from water samples, and carbon dioxide, hydrogen, methane, and carbon monoxide in gas samples to evaluate activity products for ~300 coupled oxidation-reduction reactions. Comparison of activity products and independently calculated equilibrium constants leads to values of the chemical affinity for each of the reactions, which quantifies how far each reaction is from equilibrium. Affinities, in turn, show systematic behavior that is independent of temperature but can be correlated with pH of the hot springs as a proxy for the full spectrum of geochemical variability. Many affinities are slightly to somewhat dependent on pH, while others are dramatically influenced by changes in chemical composition. All reactions involving dissolved oxygen as the electron acceptor are potential energy sources in all hot spring samples collected, but the ranking of dominant electron donors changes from ferrous iron, and sulfur at high pH to carbon monoxide, hydrogen, and magnetite as pH decreases. There is a general trend of decreasing energy yields depending on electron acceptors that follows the sequence: O2(aq)>NO3-≈NO2-≈S>pyrite≈SO4-2≈CO(g)≈CO2(g) at high pH, and O2(aq)≈magnetite>hematite≈goethite>NO3-≈NO2-≈S≈pyrite≈SO4-2 at low pH. Many reactions that are favorable sources of chemical energy at one set of geochemical conditions fail to provide energy at other conditions, and vice versa. This results in energy profiles supplied by geochemical processes that provide fundamentally different foundations for chemotrophic microbial communities as composition changes.
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U2 - 10.1016/j.gca.2009.08.036
DO - 10.1016/j.gca.2009.08.036
M3 - Article
AN - SCOPUS:77953684302
VL - 74
SP - 4005
EP - 4043
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
IS - 14
ER -