title: Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation.
abstract: 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 Ångström-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.
authors: Department of Earth and Planetary Sciences, University of California, Davis, CA 95616; oscarbranson@gmail.com hjspero@ucdavis.edu gagnon@uw.edu.
authors: Oscar
authors: 0000-0002-1851-497X
authors: O
authors: Branson
authors: School of Oceanography, University of Washington, Seattle, WA 98195.
authors: Elisa A
authors: EA
authors: Bonnin
authors: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
authors: Daniel E
authors: DE
authors: Perea
authors: Department of Earth and Planetary Sciences, University of California, Davis, CA 95616; oscarbranson@gmail.com hjspero@ucdavis.edu gagnon@uw.edu.
authors: Howard J
authors: HJ
authors: Spero
authors: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
authors: Zihua
authors: Z
authors: Zhu
authors: Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
authors: Maria
authors: M
authors: Winters
authors: Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964.
authors: Bärbel
authors: B
authors: Hönisch
authors: Department of Earth and Planetary Sciences, University of California, Davis, CA 95616.
authors: Ann D
authors: AD
authors: Russell
authors: Department of Earth and Planetary Sciences, University of California, Davis, CA 95616.|College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331.
authors: Jennifer S
authors: JS
authors: Fehrenbacher
authors: School of Oceanography, University of Washington, Seattle, WA 98195; oscarbranson@gmail.com hjspero@ucdavis.edu gagnon@uw.edu.
authors: Alexander C
authors: AC
authors: Gagnon
mesh_terms: D060105:Animal Shells / Q000737:chemistry / Q000000981:diagnostic imaging / Q000378:metabolism*; D000818:Animals; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000378:metabolism*; D056908:Foraminifera / Q000378:metabolism*; D008274:Magnesium / Q000032:analysis; D013058:Mass Spectrometry / Q000379:methods; D036103:Nanotechnology; D012964:Sodium / Q000032:analysis; D014054:Tomography / Q000379:methods
chemical_list: D012964:Sodium; D002119:Calcium Carbonate; D008274:Magnesium
keywords: biomineralization; foraminifera; geochemistry; paleoceanography; templating