Acropora robusta (Dana 1846)

zooxanthellate

Low, branching colonies, with branches sprawling in all directions, some vertically, others horizontally and then turning upwards. Branches in the centre of the colony are generally much thicker, and may simply be lumps rising from the extensive area of attachment. Branches may exceed 4 cm thick, forming some of the largest and thickest branches of the Acropora (excluding "stalks" of table Acropora). Corallites are of two main kinds: immersed or cylindrical, the latter being most common near branch tips and the former predominating on older, thicker sections. Branches have a rasp like texture. Colonies may have bases which apparently encrust the substrate for over 2 m in diameter. This species occurs in very shallow water only, where it prefers moderate rather than high exposure. It may be locally common, and completely cover areas of many square metres (Sheppard, 1998). Colonies are irregular in shape with thick conical branches at the centre and with thinner prostrate branches with upturned ends at the periphery. Radial corallites are of mixed size and shapes but are generally rasp-like. Colour: bright green with deep-pink branch tips or pinky-brown, yellow -brown or cream. Abundance: Restricted to shallow reef environments, common on reef margins exposed to strong wave action (Veron, 1986).