Origin of Short-Chain Organic Acids in Serpentinite Mud Volcanoes of the Mariana Convergent Margin
|Author(s)||Eickenbusch Philip1, Takai Ken2, Sissman Olivier3, Suzuki Shino4, Menzies Catriona5, 6, Sakai Sanae2, Sansjofre Pierre7, Tasumi Eiji2, Bernasconi Stefano M.8, Glombitza Clemens1, 9, Jorgensen Bo Barker10, Morono Yuki4, Lever Mark Alexander1|
|Affiliation(s)||1 : Swiss Fed Inst Technol, Inst Biogeochem & Pollutant Dynam, Zurich, Switzerland.
2 : Japan Agcy Marine Earth Sci Technol, SUGAR Program, Inst Extra Cutting Edge Sci & Technol Avant Garde, Yokosuka, Kanagawa, Japan.
3 : IFP Energies Nouvelles, Rueil Malmaison, France.
4 : Japan Agcy Marine Earth Sci & Technol, Kochi Inst Core Sample Res, Geomicrobiol Res Grp, Kochi, Japan.
5 : Univ Southampton, Natl Oceanog Ctr, Ocean & Earth Sci, Southampton, Hants, England.
6 : Univ Aberdeen, Dept Geol & Petr Geol, Aberdeen, Scotland.
7 : Univ Bretagne Occidentale, Lab Geosci Ocean UMR 6538, Brest, France.
8 : Swiss Fed Inst Technol, Geol Inst, Zurich, Switzerland.
9 : NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
10 : Aarhus Univ, Ctr Geomicrobiol, Dept Biosci, Aarhus, Denmark.
|Source||Frontiers In Microbiology (1664-302X) (Frontiers Media Sa), 2019-07 , Vol. 10 , N. 1729 , P. 21p.|
|WOS© Times Cited||4|
|Keyword(s)||limits of life, deep biosphere, serpentinization, abiotic synthesis, formate, acetate, methane, International Ocean Discovery Program|
Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H-2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80 degrees C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisfia, and Asut Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250 degrees C, respectively) of the underlying subducting slab, and in the porewater pH (11.0, 11.2, 12.5, respectively) of the serpentinite mud. Increases in formate and acetate concentrations across the three mud volcanoes, which are positively correlated with temperature in the subducting slab and coincide with strong increases in H(2 )concentrations, indicate a serpentinization-related origin. Thermodynamic calculations suggest that formate is produced by equilibrium reactions with dissolved inorganic carbon (DIC) + H-2, and that equilibration continues during fluid ascent at temperatures below 80 degrees C. By contrast, the mechanism(s) of acetate production are not clear. Besides formate, acetate, and H-2 data, we present concentrations of other SCOAs, methane, carbon monoxide, and sulfate, delta C-13-data on bulk carbon pools, and microbial cell counts. Even though calculations indicate a wide range of microbial catabolic reactions to be thermodynamically favorable, concentration profiles of potential energy substrates, and very low cell numbers suggest that microbial life is scarce or absent. We discuss the potential roles of temperature, pH, pressure, and dispersal in limiting the occurrence of microbial life in deep serpentinitic environments.