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).
Staghorn corals reproduce sexually or asexually. Sexual reproduction occurs via the release of eggs and sperm into the water. Most staghorn corals on the Great Barrier Reef sexually reproduce simultaneously, an incredible event that occurs soon after the full moon, from October to December. 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 kilometres away. Asexual reproduction occurs via fragmentation, when a branch breaks off a colony, reattaches to the substrate and grows (3).