Abstract:
To identify the role of zooxanthellae for bleaching recovery, this study was subdivided into three experiments; 1) The effects of temperature (27 control, 30 and 33 oC) and salinity (10, 20 and 30 psu) on the growth of zooxanthellae; 2) The combined effects of temperature and salinity on coral bleaching; 3) Use of zooxanthellae for bleaching recovery in the laboratory. This study was conducted in aquariums under laboratory conditions on cauliflower coral Pocillopora damicornis, collected from 3 sites around Samaesan Island, Chonburi, Thailand. The results showed that when coral exposed to the highest temperature (33 oC) under lowest salinity (10 psu), 50-90% bleaching was found with the highest symbiont densities in the water column detected. At this condition, zooxanthellae that isolated from 7 marine invertebrates, most cells died on day 4 of experiment and those cells in the water column were similar to normal cells in shape and size but clearly pale in colors with less cytoplasmic organelles than the normal cells. The bleached nubbins (< 5%) exposed to zooxanthellae can recovery when after the thermal stress, the temperature turns to normal condition. These results suggested that the combination of the high temperature and low salinity affect zooxanthellae and coral bleaching.