[B-CG28] 生命-水-鉱物-大気相互作用

[BCG28-03] Deep Carbonを使う鉄酸化菌

*掛川 武¹、寺島 昇吾¹、奈良 郁子¹ (1.東北大学大学院理学研究科)

キーワード：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.