Like many corals, staghorn corals have a special symbiotic relationship with algae, called zooxanthellae. The algae gain a safe, stable environment within the coral's tissues, while the coral receives nutrients produced by the algae through photosynthesis. While, on average, zooxanthellate coral can obtain around 70 percent of its nutrient requirements from zooxanthellae photosynthesis, the coral may also feed on zooplankton (3).
Staghorn corals are reef-building, or ‘hermatypic’,corals and are incredibly successful at this task for two main reasons. Firstly, they have light skeletons which allow them to grow quickly and out-compete their neighbouring corals. Secondly, the skeleton, or corallite, of a new polyp, is built by specialised ‘axial’ corallites. These axial corallites form the tips of branches and, as a result, all the corallites of a colony are closely interconnected and can grow in a coordinated manner. By harnessing the sun's energy, staghorn corals are able to grow relatively rapidly and form vast reef structures, but are constrained to live near the water surface (3).
Acropora austera releases eggs and sperm into the water column at certain times of the year in mass spawning events. The sperm and eggs combine in the water column, with a peak in egg and sperm release occurring in November in the southern Pacific Ocean. Larvae subsequently develop, and float passively in the currents as part of the zooplankton community, before settling on the ocean floor (6).