"Super-quenching" state protects Symbiodinium from thermal stress - Implications for coral bleaching

Chavdar Slavov, Verena Schrameyer, Michael Reus, Peter J. Ralph, Ross Hill, Claudia Büchel, Anthony W D Larkum*, Alfred R. Holzwarth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Citations (Scopus)


The global rise in sea surface temperatures causes regular exposure of corals to high temperature and high light stress, leading to worldwide disastrous coral bleaching events (loss of symbiotic dinoflagellates (Symbiodinium) from reef-building corals). Our picosecond chlorophyll fluorescence experiments on cultured Symbiodinium clade C cells exposed to coral bleaching conditions uncovered the transformations of the alga's photosynthetic apparatus (PSA) that activate an extremely efficient non-photochemical "super-quenching" mechanism. The mechanism is associated with a transition from an initially heterogeneous photosystem II (PSII) pool to a homogeneous "spillover" pool, where nearly all excitation energy is transferred to photosystem I (PSI). There, the inherently higher stability of PSI and high quenching efficiency of P700 + allow dumping of PSII excess excitation energy into heat, resulting in almost complete cessation of photosynthetic electron transport (PET). This potentially reversible "super-quenching" mechanism protects the PSA against destruction at the cost of a loss of photosynthetic activity. We suggest that the inhibition of PET and the consequent inhibition of organic carbon production (e.g. sugars) in the symbiotic Symbiodinium provide a trigger for the symbiont expulsion, i.e. bleaching.

Original languageEnglish
Pages (from-to)840-847
Number of pages8
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number6
Publication statusPublished - 1 Jun 2016
Externally publishedYes


  • Coral bleaching
  • Global climate change
  • Non-photochemical quenching
  • Photosynthesis
  • Symbiodinium
  • Symbiosis


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