The crown of thorns starfish (acanthaster planci), a very large starfish, is found throughout the Pacific and Indian oceans. They can grow to be as large as a half meter and begin life as a small larvae. Their primary source of food is coral, consuming many different types depending on the region. Many different theories exist on how to control an outbreak and what causes an outbreak to happen initially. The first known outbreak happened on the Great Barrier Reef in 1962, but studies of the soil indicate that the crown of thorns starfish has been on the Great Barrier Reef anywhere from 7000 to 3000 years ago.
Reproduction of the Crown of Thorns Starfish
Crown of thorns have the ability to reproduce very quickly. When during spawning season, one female can produce up to sixty million eggs. After the eggs have hatched they turn into larvae and are taken by the water current and moved throughout the ocean, thus spreading the population to areas that may not have had it before. During this larval stage they feed on algae from the surrounding water as well as pieces of dead coral. Because they have the ability to reproduce so many offspring they can easily take over an entire reef in a short period of time. Once the stars have reached two years old they are capable of actually feeding on the live coral. Until they have reached a larger size, however, they are subject to larger life forms on the reef feeding on them.
Predators Threatening the Crown of Thorns Starfish
Once the crown of thorns starfish reaches adult size it has far fewer predators, but it still has a some. One predator is the giant triton snail which has a natural tolerance to the poison from the starfish, but they have been over-poached because they have very beautiful shells. Another predator is a type of fish, the humphead maori wrasse, which has also been over-fished. There are additional predators including, but not limited to, the starry pufferfish and the titan triggerfish. The declining population of predators is one of the causes of an outbreak in the crown of thorns starfish population.
Human Influence on the Outbreak
Another possible cause is the increased pollution from humanity. There are traces that after long periods of rain, there is a higher chance of an outbreak. In theory the large amounts of rain causes runoff into the oceans. This runoff includes waters that have low salinity which helps the starfish larvae to survive. It also includes high nutrient levels in the water which causes more algae to be created and thus gives the developing starfish more to eat and a greater chance for survival. These increases lead scientists to believe that there may be more frequent outbreaks in the future and that the outbreaks will last longer.
Dangers to the Coral Reef
If the current levels of outbreak continue it seems that the current coral reefs will not be able to sustain their environment as it is. The crown of thorns is very detrimental to the coral reef and the population is in dire need of control. There needs to be much more research into how to control the population of starfish and on how to regenerate the population of the coral reef. The natural predators of the starfish have since been protected by laws to prevent overfishing. The humphead maori wrasse is now protected under the Queensland fisheries legislation that passed in 2003 and the giant triton snail have been protected since 1969. It will still take a very long time for these natural predators to recover to levels high enough to counteract the growth in the crown of thorns starfish.
Resources
AIMS Long Term Monitoring Program Survey. “ Crown of Thorns Starfish on the Great Barrier Reef. ” AIMS.gov.au. 2004. Australian Institute of Marine Science. 5 Aug. 2009.
Australian Institute of Marine Science. “ Crown of Thorns Phenomenon.” AIMS.gov.au. 2008. Australian Institute of Marine Science. 3 Aug. 2009.
Davis, Haley. “Crown of Thorn Sea star.” Encyclopedia of Earth. Ed. John Bruno. Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment, 2008.
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Tiffany Chavis - A classically trained chef, Tiffany works extensively with seafood, wild game and traditional American cuisines.
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