Fluctuations in algal chlorophyll and carotenoid pigments during solar bleaching in the coral Goniastrea aspera at Phuket, Thailand

HPLC analysis of pigments of the symbiotic algae of the coral Goniastrea aspera (Verrill) showed the presence of the chlorophylls a and c(2) (chl a and c(2)) and the carotenoids peridinin, diadinoxanthin, diatoxanthin and beta-carotene. Increased production of diatoxanthin was seen in algae extracted from the western surfaces of corals, exposed to high levels of solar radiation, during a solar bleaching event. In addition, an increase in the ratio of diatoxanthin to the total xanthophyll pool was observed in bleached tissues, together with a progressive increase in the total xanthophyll pool (relative to total chlorophyll levels) over the bleaching period. These results support a potential photoprotective function for xanthophylls in the coral/algal symbiosis. Chlorophyll breakdown products, phaeophytin a and pyrophaeophytin a, were recognised in considerable quantities only in bleached tissues. Computation of a simple chlorophyll budget showed that 45% of chl a was lost in partially bleached tissues and approximately 62% in fully bleached tissues, indicating a very rapid photodegradation of chlorophyll 24 h after exposure to high irradiance.