[Coral-List] Bleaching thresholds and the growth rate of the intracellular zooxanthellae

Scott Wooldridge S.Wooldridge at aims.gov.au
Thu Jul 5 18:23:35 EDT 2012

Traditionally, warm-water coral bleaching has been considered to be the direct result of thermal inhibition of the photosynthetic machinery of the algal endosymbiont (‘zooxanthellae’). However, the scientific evidence for such a conclusion is inconclusive (e.g., a large portion of the expelled zooxanthellae remain photosynthetically competent; Ralph et al. (2001), MEPS 220, 163-168). For those who are pleased to conceive of ideas beyond the existing paradigm, I offer a new perspective essay which considers the possibility that the onset of the bleaching syndrome (and setting of upper thermal bleaching limits) are emergent attributes of the coral symbiosis that are ultimately underpinned by the characteristic growth profile of the intracellular zooxanthellae; which are known to depend not just on temperature, but also external (seawater) nutrient availability and zooxanthellae genotype.

The essay, “Breakdown of the coral-algae symbiosis: towards formalising a linkage between warm-water bleaching thresholds and the growth rate of the intracellular zooxanthellae”, is now accessible and open for Interactive Public Discussion until 30 Aug 2012 at:


Scott Wooldridge

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