According to a study by Australia’s Government Institute of Marine Sciences and the University of Wollongong, damage to coral cover on the Great Barrier Reef is caused by tropical cyclones (48 percent), crown-of-thorns starfish (42 percent) and coral bleaching (10 percent). The government estimates that the reef has lost more than 50 percent of its coral cover since the mid-1980s. While the government can’t mitigate damage from cyclones or coral bleaching, it can do something in an effort to reduce the damage caused by the crown-of-thorns starfish (Acanthaster planci). If nothing is done, within 10 years, the Great Barrier Reef will lose another 50 percent of its coral cover, the report said.
The crown-of-thorns starfish at the larval stage feed on plankton. The populations of these microscopic organisms flourish when chemical fertilizers make it into the ocean, which in turn leads to more starfish than the reef can handle. The last outbreak of the crown-of-thorns starfish occurred in the 1990s. As adults, these starfish feed on coral by climbing up onto them and releasing digestive enzymes onto the corals which liquefy the corals so the starfish can consume them.
According to the report, the crown-of-thorns starfish can eat up to a foot of coral daily. The number one solution, according to the World Wildlife Fund Australia, is to reduce the use of chemical fertilizers that end up in the ocean and feed the planktons that are in turn eaten by the larval starfish. Other solutions include injecting the starfish with an acid and cutting the starfish up. These methods were conducted before with little effect on the population of the starfish. If the starfish were removed from the reef in significant numbers, the reef would cover at a rate of just less than 1 percent each year, the report said.