Acropora hemprichii (Ehrenberg 1834)

zooxanthellate

This species can form extensive, monospecific carpets of crowded branches 20-30 cm tall. Branches are distinctively covered with swollen radial corallites which are bead shaped to spherical, up to 3 or 4 mm diameter, each containing a calice 1 mm in diameter. The corallites are arranged in rows on young, thinner branches but are usually irregular on thick branches. In deeper water, tall colonies may be conspicuous, especially when coloured a strong blue or purple. This species forms extensive stands on moderately exposed, shallow reefs, particularly between 3-10 m deep on outer patch reefs, exposed fringing reefs and in open lagoons. It is not uncommon to 20 m deep, though it rarely develops into large patches below 10 m; in deeper water single colonies occur, where they usually grow into taller colonies. It is usually yellow or a strong blue. Acropora austera appears very similar to A. hemprichi and the latter name has also been used, though A. austera from the Indian Ocean is a considerably larger coral (Sheppard, 1998).