Environmental Threats To The Great Barrier Reef - Crown-of-thorns Starfish

Crown-of-thorns Starfish

The Crown-of-Thorns Starfish is a coral reef predator which preys on coral polyps by climbing onto them, extruding its stomach over them, and releasing digestive enzymes to absorb the liquified tissue. An individual adult of this species can eat up to six square metres of living reef in a single year. Geological evidence suggests that the Crown-of-Thorns Starfish has been part of the Great Barrier Reef's ecology for "at least several thousand years", but there is no geological evidence for Crown-of-Thorns outbreaks. Large outbreaks of these starfish can devastate reefs. In 2000, an outbreak contributed to a loss of 66% of live coral cover on sampled reefs in a study by the CRC Reefs Research Centre. Although large outbreaks of these starfish are believed to occur in natural cycles, human activity in and around the Great Barrier Reef can worsen the effects. Reduction of water quality associated with agriculture can cause the crown-of-thorns starfish larvae to thrive. Overfishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of crown-of-thorns starfish. The CRC Reef Research Centre defines an outbreak as when there are more than 30 adult starfish in an area of one hectare.