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, a 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 forming reefs for two main reasons. Firstly, they have light skeletons which allow them to grow quickly and out-compete 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 through the zooxanthellae, staghorn corals are able to grow relatively rapidly and form vast reef structures, but are constrained to live near the water surface (3).
Staghorn corals reproduce sexually or asexually. Sexual reproduction occurs via the release of eggs and sperm into the water. Streams of pinkish eggs are released from corallites on the sides of branches, to be fertilised by sperm released from other polyps at the same time. The water turns milky from all the eggs and sperm released from thousands of colonies. Some of the resulting larvae settle quickly on the same reef, whilst others may drift around for months, finally settling on reefs hundreds of kilometers away. Asexual reproduction occurs via fragmentation, when a branch breaks off a colony, reattaches to the substrate and grows into a new colony (3).