title: Nano-scale spatial assessment of calcium distribution in coccolithophores using synchrotron-based nano-CT and STXM-NEXAFS.
abstract: Calcified coccolithophores generate calcium carbonate scales around their cell surface. In light of predicted climate change and the global carbon cycle, the biomineralization ability of coccoliths has received growing interest. However, the underlying biomineralization mechanism is not yet well understood; the lack of non-invasive characterizing tools to obtain molecular level information involving biogenic processes and biomineral components remain significant challenges. In the present study, synchrotron-based Nano-computed Tomography (Nano-CT) and Scanning Transmission X-ray Microscopy-Near-edge X-ray Absorption Fine Structure Spectromicroscopy (STXM-NEXAFS) techniques were employed to identify Ca spatial distribution and investigate the compositional chemistry and distinctive features of the association between biomacromolecules and mineral components of calcite present in coccoliths. The Nano-CT results show that the coccolith scale vesicle is similar as a continuous single channel. The mature coccoliths were intracellularly distributed and immediately ejected and located at the exterior surface to form a coccoshpere. The NEXAFS spectromicroscopy results of the Ca L edge clearly demonstrate the existence of two levels of gradients spatially, indicating two distinctive forms of Ca in coccoliths: a crystalline-poor layer surrounded by a relatively crystalline-rich layer. The results show that Sr is absorbed by the coccoliths and that Sr/Ca substitution is rather homogeneous within the coccoliths. Our findings indicate that synchrotron-based STXM-NEXAFS and Nano-CT are excellent tools for the study of biominerals and provide information to clarify biomineralization mechanism.
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. shysun@swust.edu.cn.
authors.forename: Shiyong
authors.initials: S
authors.lastname: Sun
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. yyc930124@163.com.
authors.forename: Yanchen
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. zxiang3354@163.com.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zou
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. shenglanfan@163.com.
authors.forename: Shenglan
authors.initials: S
authors.lastname: Fan
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. kingchou1314@163.com.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. qw_dai@163.com.
authors.forename: Qunwei
authors.initials: Q
authors.lastname: Dai
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. fqdong@swust.edu.cn.
authors.forename: Faqin
authors.initials: F
authors.lastname: Dong
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. dragonlmx@126.com.
authors.forename: Mingxue
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. xiaoqin_nie@163.com.
authors.forename: Xiaoqin
authors.initials: X
authors.lastname: Nie
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. tdyduff@hotmail.com.
authors.forename: Daoyong
authors.initials: D
authors.lastname: Tan
authors.affiliation: Department of Geological and Mineral Engineering, Key Laboratory of Solid Waste Treatment and Resource Recycle & Fundamental Science on Nuclear Waste and Environmental Security Laboratory, Southwest University of Science and Technology, Mianyang 621010, China. zmclishuai88@163.com.
authors.forename: Shuai
authors.initials: S
authors.lastname: Li
mesh_terms: D002118:Calcium / Q000378:metabolism*; D058087:Haptophyta / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D056928:X-Ray Absorption Spectroscopy; D055114:X-Ray Microtomography
chemical_list: D002118:Calcium