Influences of coral genotype and seawater pCO2 on skeletal Ba/Ca and Mg/Ca in cultured massive Porites spp. corals

N. Allison, C. Cole, C. Hintz, K. Hintz, A. A. Finch

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4 Citations (Scopus)
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Abstract

Coral skeletal Ba/Ca is a proxy for seawater Ba/Ca, used to infer oceanic upwelling and terrigenous runoff while [Mg2+] is implicated in the control of coral biomineralisation. We cultured large individuals (>12 cm diameter) of 3 genotypes of massive adult Porites spp. corals over a range of seawater pCO2 to test how atmospheric CO2 variations affect skeletal Ba/Ca and Mg/Ca. We identified the skeleton deposited after a 5 month acclimation period and analysed the skeletal Ba/Ca and Mg/Ca by secondary ion mass spectrometry. Skeletal Mg/Ca varies significantly between some duplicate colonies of the same coral genotype hampering identification of genotype and seawater pCO2 effects. Coral aragonite:seawater Ba/Ca partition coefficients (KD Ba/Ca) do not vary significantly between duplicate colonies of the same coral genotype. We observe large variations in KD Ba/Ca between different massive Porites spp. coral genotypes irrespective of seawater pCO2. These variations do not correlate with coral calcification, photosynthesis or respiration rates or with skeletal KD Mg/Ca or KD Sr/Ca. Seawater pCO2 does not significantly affect KD Ba/Ca in 2 genotypes but KD Ba/Ca is significantly higher at 750 μatm seawater pCO2 than at 180 μatm in 1 P. lutea genotype. Genotype specific variations in KD Ba/Ca between different Porites spp. could yield large errors (~250%) in reconstructions of seawater Ba when comparing Ba/Ca between corals. Analysis of fossil coral specimens deposited at low seawater pCO2, may underestimate past seawater Ba/Ca and ocean upwelling/freshwater inputs when compared with modern specimens but the effect is small in comparison with the observed difference between coral genotypes.
Original languageEnglish
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
VolumeIn press
Early online date11 Jun 2018
DOIs
Publication statusE-pub ahead of print - 11 Jun 2018

Keywords

  • Calcification
  • Photosynthesis
  • Respiration
  • KD Ba/Ca
  • KD Mg/Ca
  • Coral

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