Japan Geoscience Union Meeting 2015

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Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG28] Interrelation between Life, Water, Mineral, and Atmosphere

Tue. May 26, 2015 12:00 PM - 12:45 PM 105 (1F)

Convener:*Fumito Shiraishi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Yohey Suzuki(Graduate School of Science, The University of Tokyo), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Naganuma(Graduate School of Biosphere Science), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Kentaro Nakamura(Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Chair:Takeshi Naganuma(Graduate School of Biosphere Science), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology)

12:30 PM - 12:45 PM

[BCG28-03] Anoxic Fe-oxidizing bacteria are using deep carbon in hot spring environments

*Takeshi KAKEGAWA1, Shogo TERAJIMA1, Fumiko NARA1 (1.Graduate School of Science, Tohoku University)

Keywords:Deep Carbon, Fe-oxidizing, hot spring

Oku-oku hachikuro hot spring is discharging anoxic, CO2- and Fe-rich water. Hot spring water is flowing in distance from vent forming carbonate terrace. Various forms of aragonite (bundle of needle shape, radial aggregates, plate, etc.) comprise terrace. Those aragonites are most likely formed by inorganic processes. Near the vent, significant amounts of iron hydroxides are precipitating. Microscopic and SEM observation identified two forms of iron hydroxides; iron hydroxides covering sheath and stromatolite-like aggregates. Fe-rich precipitates disappear with distance where cyanobacteria start to form mats. Stable carbon isotope compositions of Fe-oxidizing bacteria are similar to that of cyanobacteria. However, radiogenic carbon isotope compositions are significantly different between Fe-oxidizing bacteria and cyanobacteria. Cyanobacteria are using atmospheric CO2 with abundant 14C. But Fe-oxidizing bacteria are using dead carbon derived from deep underlying rocks rather than atmospheric CO2. Those data may constrain carbon ecosystem of Fe-oxidizing bacteria in anoxic hot spring environments.