[B-PT02_1PO1] Biocalcification and the Geochemistry of Proxies

[BPT02-P03] 有孔虫細胞軟組織のNanoSIMSによる窒素同位体比マッピング

*野牧 秀隆¹、石田 章純²、白井 厚太朗²、力石 嘉人¹、植松 勝之³、多米 晃裕³、土屋 正史¹、豊福 高志¹、高畑 直人²、佐野 有司²、大河内 直彦¹ (1.海洋研究開発機構、2.東京大学大気海洋研究所、3.マリン・ワーク・ジャパン)

キーワード：底生有孔虫, 硝酸塩呼吸, 共生微生物, 高分解能二次イオン質量分析装置

Shallow water benthic foraminifera, Ammonia beccarii, survive under anoxic conditions in conjunction with possible endobionts. Based on the amino acid analysis, those endobionts are expected to utilize nitrate pool in the foraminifera. However, nitrogen cycles in the foraminiferal cell and endobionts are still unclear. Here, we obtained two dimensional-nitrogen isotopic compositions of A. beccarii which had been incubated under oxic and anoxic conditions with ¹⁵N-labeled nitrate. After observing with transmission electron microscope to confirm cellular ultrastructure and endobiont distribution, same ultra thin section was examined for nitrogen isotopic composition analysis using secondary ion mass spectrometer. Nitrogen isotopic compositions were measured with spatial resolution better than 400 nm. ¹⁵N-enriched parts were found in certain structures in the cell, but not in the endobionts in this experiment.