The influence of seawater calcium ions on coral calcification mechanisms: Constraints from boron and carbon isotopes and B/Ca ratios in Pocillopora damicornis

Sharmila J. Giri, Peter K. Swart, Ali Pourmand

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

In order to better understand the response of coral calcification to changes in seawater chemistry, fragments of the coral Pocillopora damicornis were grown in seawater with varying [Ca2+]. Using a combined trace element (B/Ca) and stable isotope (δ11B, δ13C) approach, this paper explores the effect of seawater calcium concentrations ([Ca2+]SW) on coral calcification mechanisms and describes the manipulation of the extracellular calcifying fluid (ECF) pH (pHECF), saturation state (ΩECF) and dissolved inorganic carbon (DIC) speciation of the ECF. In these experiments, increases in [Ca2+]SW did not significantly influence calcification rates but caused the skeletal B/Ca ratio to significantly increase. To explain these results we propose a mechanism by which [CO3 2−]ECF is influenced by [Ca2+]SW. This mechanism suggests that the pHECF will be lowest in our highest [Ca2+] treatment and using this relationship we can place constraints on the pHECF. The difference in pHECF in our treatments is supported in part by a slight, but insignificant decrease in skeletal δ11B and δ13C values. We propose a novel dual-proxy approach to estimate pHECF, where calcification occurs at a pHECF > 9. This work emphasizes the importance of multi-element proxy approaches in understanding pH up-regulation and CO3 2− concentrations during calcification of corals.

Original languageEnglish (US)
Pages (from-to)130-140
Number of pages11
JournalEarth and Planetary Science Letters
Volume519
DOIs
StatePublished - Aug 1 2019

Keywords

  • boron
  • carbon isotopes
  • dissolved inorganic carbon
  • pH proxy
  • seawater chemistry

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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