[B-PT02] Biomineralization and Geochemistry of Proxies

[BPT02-P08] In Situ Observation of Intracellular Element Composition during Chamber Formation In Benthic Forainifera Utilizing Cryo-FIB-SEM

*Takashi Toyofuku^1,2, Yukiko Nagai¹ (1.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2.Tokyo University of Marine Science and Technology)

Keywords:foraminifera, biomineralization

Calcareous foraminifera are marine unicellular organisms that form calcareous tests with calcite. The trace element composition of these tests is an important environmental proxy in the field of paleoceanography. Previous our studies have revealed the processes of their uptake from seawater using imaging techniques for pH and calcium and FIB-SEM for microstructure observation, but the intracellular distribution of elements has not been fully understood. The purpose of this study is to measure the intracellular elemental distribution during the chamber formation process of Ammonia confertista, which has been studied due to its ease of laboratory culture. We specifically detected the elements in the cells and their formation chambers in the chamber formation stages. For this purpose, we adapted the sandwich freezing method commonly used in bacterial pretreatment to freeze foraminifera during chamber formation. At the stage of foraminifera chamber formation, the foraminifera were fixed to a cryostat stab and frozen in liquid propane cooled with liquid nitrogen. The frozen samples were processed by Cryo-FIB-SEM-EDS, and the foraminifera chambers and cells were observed for elemental detection by EDS. EDS measurements revealed the presence of carbon (C), nitrogen (N), oxygen (O), calcium (Ca), magnesium (Mg), phosphorus (P), sulfur (S), and chlorine (Cl) in the cells, with elements such as Ca, Mg, and P concentrated in specific certain sites. This study provides insight into the mechanisms of element management during chamber formation in Ammonia confertitesta, contributes to our understanding of foraminiferal biomineralization.