[M-IS18] 古気候・古海洋変動

[MIS18-P23] 珪藻殻化学分析の高精度化に向けたタクサごとの分離手法の確立

★招待講演

*加藤 悠爾¹、諸野 祐樹²、井尻 暁³、寺田 武志⁴、池原 実⁵ (1.筑波大学 生命環境系、2.海洋研究開発機構　高知コア研究所、3.神戸大学、4.マリン・ワーク・ジャパン、5.高知大学　海洋コア総合研究センター)

キーワード：珪藻、南大洋、セルソーター、国際深海科学掘削計画

In order to perform accurate geochemical analysis on diatom fossils preserved in sediments, it is necessary to extract diatom frustules by taxon. However, due to the small size of diatoms, the purification of diatom taxa has not been achieved so far, and therefore, previous geochemical analysis on diatom frustules has been performed with a mixture of various taxa. In order to solve this problem, we attempted to extract diatom fossils by taxon using a cell sorter, an instrument that has been used in the field of life sciences. We used six samples from a sediment core International Ocean Discovery Program (IODP) Expedition 382 Hole U1538A, which was drilled in the Scotia Sea, Atlantic sector of the Southern Ocean. After the pretreatment process including removal of organic matter, carbonates, and clay minerals, which was followed by sieving to select 20–32 μm fraction, we conducted cell sorter experiments focusing on both optical and fluorescence characteristics of the particles (diatom fossils). As a result, we succeeded in extracting five diatom taxa with high purity: (1) discoid diatoms (mainly genus Thalassiosira) that have moderate degree of fluorescence; (2) pennate diatoms (mainly Fragilariopsis) that have the highest fluorescence values; (3) genus Rhizosolenia; (4) Eucampia antarctica; (5) needle-shaped diatoms (genus Thalassiothrix). The establishment of diatom purification method enables us to conduct more accurate geochemical analysis such as oxygen isotope ratio δ¹⁸O of diatom frustules, which is likely to lead to significant advance of paleoceanography especially at high latitudes or upwelling zones where diatoms are abundant.