After 25 days, the seawater temperature for all tanks was gradually elevated to 31 °C over 2 days (1 °C increase every 12 h) and was kept at 31 °C for the following 7 days. Nutrient conditions at 31 °C were maintained in the same manner as those at 27 °C. The measurement of algal release rate (AR) from the corals and subsequent coral tissue extraction were conducted on the last day of the 27 °C treatment (n = 24) and on the seventh day after the temperature was elevated to 31 °C (n = 24). The positions of corals and tanks were regularly changed to minimize the position effect.