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Pulse–amplitude–modulation chlorophyll fluorometry was used to examine changes in dark-adapted Fv/Fm of endosymbiotic dinoflagellate microalgae within the tissues of the temperate coral Plesiastrea versipora exposed to elevated seawater temperature. The Fv/Fm was markedly reduced following exposure of corals to 28°C for 48 h. When corals were returned to ambient (24°C) conditions, Fv/Fm increased in an initial rapid and then secondary slower phase. Tissue discolouration (coral bleaching), caused by a significant decrease in the density of algae, was observed during the first 2–3 days of the recovery period. After 14 days, Fv/Fm was still significantly lower than in control corals. The recovery of Fv/Fm is discussed in terms of repair processes within the symbiotic algae, division of healthy algae and also the selective removal of photo-damaged dinoflagellates. Under field conditions, bleached corals …