The response of coral skeletal nano-structure and hardness to ocean acidification conditions

Chao Dun Tan, Georg Haehner, Susan Fitzer, Catherine Sarah Cole, Adrian Anthony Finch, Christopher James Hintz, Kenneth Hintz, Nicola Allison*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

Ocean acidification typically reduces coral calcification rates and can fundamentally alter skeletal morphology. We use atomic force microscopy (AFM) and microindentation to determine how seawater pCO2 affects skeletal structure and Vickers hardness in a Porites lutea coral. At 400 µatm, the skeletal fasciculi are composed of tightly packed bundles of acicular crystals composed of quadrilateral nanograins, approximately 80–300 nm in dimensions. We interpret high adhesion at the nanograin edges as an organic coating. At 750 µatm the crystals are less regular in width and orientation and composed of either smaller/more rounded nanograins than observed at 400 µatm or of larger areas with little variation in adhesion. Coral aragonite may form via ion-by-ion attachment to the existing skeleton or via conversion of amorphous calcium carbonate precursors. Changes in nanoparticle morphology could reflect variations in the sizes of nanoparticles produced by each crystallization pathway or in the contributions of each pathway to biomineralization. We observe no significant variation in Vickers hardness between skeletons cultured at different seawater pCO2. Either the nanograin size does not affect skeletal hardness or the effect is offset by other changes in the skeleton, e.g. increases in skeletal organic material as reported in previous studies.
Original languageEnglish
Article number230248
Number of pages15
JournalRoyal Society Open Science
Volume10
Issue number8
Early online date2 Aug 2023
DOIs
Publication statusPublished - 2 Aug 2023

Keywords

  • CaCO3
  • Mechanical properties
  • Biomineralisation
  • Environmental change

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