Growth rates of the two reef-building species, Acropora humilis and Millepora platyphylla at Hurghada, Red Sea, Egypt

Linear growth rates were measured for two species of coral namely, Acropora humilis and Millepora platyphylla in Hurghada during the period from autumn 2006 to summer 2007. In addition, the rates of recovery in man-made lesion in M. platyphylla were estimated on seasonal basis. The linear growth rates of A. humils varied significantly according to the sheltering condition, with an overall mean of 8.89 and 6.98mm/year in exposed and sheltered sites. The highest linear growth rate of A. humilis was estimated at the exposed site of Gotta Abu Ramada, being 9.17mm/year, while the lowest rate of 6.61mm/year was recorded at the sheltered site of El-Fanadir Reef. The seasonal linear growth rates of M. platyphylla were affected significantly by the sheltering condition, and non-significantly by seasons. The estimated annual growth rates of M. platyphylla at the exposed sites averaged higher value of 15.65mm/year compared to 11.29mm/year at the sheltered sites. On the seasonal level, the highest overall mean of growth rates was recorded in spring, while the lowest mean was in autumn, being 3.72 and 3.06mm/season, respectively. The rates of diametric lesions recovery of M. platyphylla varied significantly according to seasons and non-significantly according to sheltering condition. The fastest recovery was recorded in summer, while the lowest recovery was in winter. For instance, the lesions of 3847mm^2 area each, recovered completely within 6 weeks in summer, while the same lesions area were not recovered completely after 12 weeks in winter.