An estimated 20 percent of the world’s coral reefs have already been destroyed (6), and around a third of all reef-building coral species are now threatened with extinction (7). The major threat to corals is global climate change, with the expected rise in ocean temperatures increasing the risk of coral ‘bleaching’, in which the stressed coral expels its zooxanthellae, often resulting in the death of the coral. Climate change may also lead to more frequent, severe storms, which can damage reefs, and rising carbon dioxide levels may make the ocean increasingly acidic, reducing the ability of coral to create its hard skeleton. Such stresses can also make corals more susceptible to disease, parasites and predators, such as the crown of thorns sea star (Acanthaster planci) (1) (5) (6) (7).
These global threats are compounded by localised human impacts, such as coral harvesting, disturbance by fisheries, irresponsible tourism, invasive species, pollution and sedimentation (1) (5) (6) (7). Although Acanthastrea hillae is still widespread and common throughout its range, it is thought to be moderately susceptible to a number of threats, including bleaching (1). It also appears to be quite common in the live aquarium trade, although the extent of this and its potential impacts are unknown.