Growth Rates of Three Symbiotic Corals in the Red Sea

Growth rates of the hydrocoral Millepora dichotoma and the corals Acropora variabilis and Stylophora pistillata were studied by applying the buoyant weighing technique and statistical analysis. We found that M. dichotoma exhibited the slowest relative growth, whereas S. pistillata and A. variabilis were faster growers, with weight-based doubling times of about 3, 1.2, and 1.3 yr, respectively. In the case of A. variabilis, as well as in bladed colonies of M. dichotoma, growth rate per unit weight was size independent, whereas in S. pistillata a clear positive correlation was found between the relative growth rates and the initial colony buoyant weights. M. dichotoma and A. variabilis demonstrated distinct seasonal growth oscillations (2-month time lag with respect to the seasonal trend of the ambient water temperature). We conclude that the oscillations in the absolute growth rate of corals resulted from the seasonal changes in water temperature.