Planktic foraminifera form their shells via metastable carbonate phases

The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable...

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Bibliographic Details
Published in:Nature communications 2017-11, Vol.8 (1), p.1265-9, Article 1265
Main Authors: Jacob, D. E., Wirth, R., Agbaje, O. B. A., Branson, O., Eggins, S. M.
Format: Article
Language:English
Subjects:
704/2151/330
704/829/827
Archives & records
Calcite
Calcium
Calcium carbonate
Carbon cycle
Carbon dioxide
Climate
Crystallization
Fourier transforms
Geochemistry
Humanities and Social Sciences
Marine sediments
Metastable phases
Mineralization
multidisciplinary
Neogloboquadrina dutertrei
Ocean surface
Orbulina universa
Precipitation
Rainfall
Science
Science (multidisciplinary)
Scientific imaging
Sediments
Shells
Trace elements
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Summary:The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polymorph vaterite, implying a non-classical crystallisation pathway involving metastable phases that transform ultimately to calcite. The current understanding of how planktic foraminifer shells record climate, and how they will fare in a future high-CO 2 world is underpinned by analogy to the precipitation and dissolution of inorganic calcite. Our findings require a re-evaluation of this paradigm to consider the formation and transformation of metastable phases, which could exert an influence on the geochemistry and solubility of the biomineral calcite. Understanding foraminifera mineralisation pathways is essential to correctly decipher the geochemical climate signals recorded in their shells. Here, the authors identify a non-classical crystallization pathway via metastable phases for Orbulina universa and Neogloboquadrina dutertrei .
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-017-00955-0