Planktic foraminifera form their shells by attachment of metastable carbonate particles
Abstract
Planktic foraminifera shells contribute up to half the inorganic carbon exported from the surface ocean to the seafloor. Their tiny calcium carbonate shells are preserved in sediments as calcite, and provide our most valuable geochemical archive of changes surface ocean conditions and climate spanning the last 100 million years. Here we show the shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei consist of nano-particulate vaterite and amorphous calcium carbonate. This indicates formation via a non-classical crystallization pathway involving metastable carbonate intermediate phases before transforming to calcite, and requires a new perspective on how geochemical proxies are incorporated into planktic foraminifer shells. Our findings indicate planktic foraminifer shells could be far more susceptible to dissolution and ocean acidification than previously thought, and account for unexpected shell dissolution above the calcite saturation horizon in the ocean, which is a major uncertainty in modelling oceanic carbon fluxes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B21C0452W
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 1042 Mineral and crystal chemistry;
- GEOCHEMISTRYDE: 4825 Geochemistry;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL