期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：46
页码：12934-12939
DOI：10.1073/pnas.1522864113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceMany marine organisms build complex CaCO3 shells, which record an archive of past climate in their trace chemistry. Organic-mineral interactions are a crucial, poorly understood aspect of shell formation, which may alter shell composition and bias climate records. We map the chemistry of an organic template preserved within a type of shell that is widely used in studies of past climate. We find that the organic template embedded within this shell is enriched in Na and Mg, and can locally influence shell composition. Atom-scale maps of template chemistry offer a detailed view of the chemical interactions at an organic mineral template, and suggest that elements other than Ca2+ may be important in defining the energetics of CaCO3 nucleation during biomineralization. Plankton, corals, and other organisms produce calcium carbonate skeletons that are integral to their survival, form a key component of the global carbon cycle, and record an archive of past oceanographic conditions in their geochemistry. A key aspect of the formation of these biominerals is the interaction between organic templating structures and mineral precipitation processes. Laboratory-based studies have shown that these atomic-scale processes can profoundly influence the architecture and composition of minerals, but their importance in calcifying organisms is poorly understood because it is difficult to measure the chemistry of in vivo biomineral interfaces at spatially relevant scales. Understanding the role of templates in biomineral nucleation, and their importance in skeletal geochemistry requires an integrated, multiscale approach, which can place atom-scale observations of organic-mineral interfaces within a broader structural and geochemical context. Here we map the chemistry of an embedded organic template structure within a carbonate skeleton of the foraminifera Orbulina universa using both atom probe tomography (APT), a 3D chemical imaging technique with [IMG]f1.gif" ALT="A" BORDER="0">ngstrom-level spatial resolution, and time-of-flight secondary ionization mass spectrometry (ToF-SIMS), a 2D chemical imaging technique with submicron resolution. We quantitatively link these observations, revealing that the organic template in O. universa is uniquely enriched in both Na and Mg, and contributes to intraskeletal chemical heterogeneity. Our APT analyses reveal the cation composition of the organic surface, offering evidence to suggest that cations other than Ca2+, previously considered passive spectator ions in biomineral templating, may be important in defining the energetics of carbonate nucleation on organic templates.
