Inhibition of photosynthetic CO₂ fixation in the coral Pocillopora damicornis and its relationship to thermal bleaching

Ross Hill*, Milán Szabó, Ateeq Ur Rehman, Imre Vass, Peter J. Ralph, Anthony W.D. Larkum

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


Two inhibitors of the Calvin-Benson cycle [glycolaldehyde (GA) and potassium cyanide (KCN)] were used in cultured Symbiodinium cells and in nubbins of the coral Pocillopora damicornis to test the hypothesis that inhibition of the Calvin-Benson cycle triggers coral bleaching. Inhibitor concentration range-finding trials aimed to determine the appropriate concentration to generate inhibition of the Calvin-Benson cycle, but avoid other metabolic impacts to the symbiont and the animal host. Both 3 mmol l-1 GA and 20 uμmol l-1 KCN caused minimal inhibition of host respiration, but did induce photosynthetic impairment, measured by a loss of photosystem II function and oxygen production. GA did not affect the severity of bleaching, nor induce bleaching in the absence of thermal stress, suggesting inhibition of the Calvin-Benson cycle by GA does not initiate bleaching in P. damicornis. In contrast, KCN did activate a bleaching response through symbiont expulsion, which occurred in the presence and absence of thermal stress. While KCN is an inhibitor of the Calvin-Benson cycle, it also promotes reactive oxygen species formation, and it is likely that this was the principal agent in the coral bleaching process. These findings do not support the hypothesis that temperature-induced inhibition of the Calvin-Benson cycle alone induces coral bleaching.

Original languageEnglish
Pages (from-to)2150-2162
Number of pages13
JournalJournal of Experimental Biology
Issue number12
Publication statusPublished - 1 Jun 2014
Externally publishedYes


  • Calvin-Benson cycle
  • Coral bleaching
  • Dark reactions
  • Heat stress
  • Photoinhibition
  • Photosynthesis
  • Respiration
  • Symbiodinium


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