Chl a concentration in the methanol solution was measured with a spectrophotometer (UV-1800, Shimadzu, Kyoto, Japan) according to Ritchie (2006). The algal abundance and Chl a amount were normalized to the unit surface area of the coral skeleton, which was measured using the aluminum foil method ( Marsh, 1970). The percentage of an algal release rate (AR%) to the standing stock was calculated by dividing AR (cells cm− 2 h− 1) by the corresponding symbiotic algal density in the coral tissue (cells cm− 2).