Abstract
Corals form their reef-building aragonite (CaCO3) skeletons via transient precursor phases yet understanding of the dynamics of these early-stage transformations remains incomplete. Using time-independent myriad mapping (MM) at 50 nm resolution, we map five mineral phases near the skeleton surface of Stylophora pistillata corals grown in varying seawater pH. All precursors, crystalline and amorphous, exhibit a consistent exponential decay from the growth front, with a shared decay length of 0.7 ± 0.1 μm, independent of time, phase, or pH. This spatial decay, paired with the constant growth rate of the skeleton, reveals a decay time of 5.1 ± 0.5 minutes. The dominant precursor is not amorphous but crystalline: calcium carbonate hemihydrate (CCHH, CaCO₃·½H₂O). These results suggest that exponential crystallization kinetics govern coral biomineralization and may be a widespread feature in biogenic, geologic, and synthetic systems—traceable long after initial mineral deposition.
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Data availability
The precursor proportions generated in this work from MMs and Stylophora pistillata coral nubbin growth data have been deposited in the data.xlsx file available on Zenodo and GitHub57 with https://doi.org/10.5281/zenodo.18175786 and are source data to reproduce Figs. 2C, D, 3B, 4B, C and 5B, Supplementary Figs. 2 and 4–6, Table 1, and Supplementary Tables 2–4. The data used to produce MMs is available with no restricted access and can be obtained by contacting the corresponding author of this work at any period after publication of this work.
Code availability
GG Macros v1.0.0, Igor Pro 8, MATLAB R2023b, Python 3.11.3, Numpy 1.24.3, Pandas 2.0.1, Scipy 1.10.1, and Matplotlib 3.7.1 are used in available code, demsontrations, and software. Interactive demonstrations of the PPD code, performing exponential fits, plotting data, and the kinetic model, are publicly accessible at the following Zenodo57 and GitHub with https://doi.org/10.5281/zenodo.18175786. From available code demonstrations, all results presented in this work can be reproduced by any interested readers. Additionally, the software to produce MMs from PEEM data is available on Zenodo48 and GitHub with https://doi.org/10.5281/zenodo.17314121.
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Acknowledgements
The authors thank Aiden Gustafson and James J. De Yoreo for scientific discussions, M. Cristina Castillo Alvarez and Connor A. Schmidt for assistance during sample preparation and PEEM data acquisition, and Andreas Scholl for technical help during PEEM measurements. This work was supported by the National Science Foundation Graduate Research Fellowship Program (grant DGE-1747503) (Z.R.). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1747503. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division at the University of Wisconsin–Madison (grant DE-FG02-07ER15899) (P.G.) and at Lawrence Berkeley National Laboratory (grant FWP-FP00011135) (P.G.), and by the National Science Foundation Biomaterials Program (grant DMR-2220274) (P.G.). This research used resources of the Advanced Light Source, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-05CH11231.
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P.G., I.L., and Z.R. conceptualized the study and carried out the investigation. E.T., S.T., and A.V. provided samples. P.G., I.L., Z.R., and B.A. performed PEEM data acquisition. M.M. production was carried out by I.L., S.A., N.B., N.C., B.D.-K., J.D., A.L., S.L., R.R., L.S., J.L.S., J.S.S., C.W., J.Y., Z.R., and P.G. I.L. and Z.R. performed the data analysis. P.G. and Z.R. acquired funding. P.G. and Z.R. wrote the original draft of the manuscript. P.G., Z.R., and all co-authors reviewed and edited the manuscript.
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Rechav, Z., Tambutté, E., LeCloux, I.M. et al. Exponential crystallization in corals. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69215-4
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DOI: https://doi.org/10.1038/s41467-026-69215-4
