Australia’s Great Barrier Reef, located off the northeast coast is a truly wondrous sight to behold. A place to scuba dive, bask in the sun and home to the invasive Crown Of Thorns Starfish who is threatening the very existence of not only this reef, but also surrounding younger reefs.
This Starfish is an important part of the Reef’s own ecosystem, but when numbers get high on a per acre basis, effects to the other living coral formations are devastating. The Starfish slowly creeps along the floor of the reef, fixing itself to the coal and promptly sucks and digests living tissue, leaving a trail of lifeless brown coral in it’s wake. While not all of the reef is affected at one time, and some outlying reefs have not been affected at all, scientists have concluded that the north south prevalence of these predators is consistent with the larvae being shifted on the ocean’s currents.
Noticeable outbreaks in numbers have been recorded as far back as the early sixties, but diving technology before this time was not sufficient to provide detail on numbers or changes in it’s location.
Since it is possible for a reef to recover from such an invasion once the Starfish moves on, there is hope. It does however depend on what type of coral has been consumed, since different species of coral would obviously take more time to regrow than others.
There are at least two types of small crab which can act as a protector to the coral, although not a 100% positive solution. These crabs Trapezia and Tetralia, live in and around the coral type Pocilloporid and the Trapezia can attack the Starfish who begin devouring it by breaking it’s sharp spines. The Tetralia is said to attack the feet of the Starfish. A further problem is, once damaged, the Starfish also has the ability to regenerate itself.
Some fish are known to eat the Starfish, and ingesting the younger ones is much easier due to the spines. The Starry Puffer Fish is one such fish, although consuming Starfish at a rate of just one per week each is not likely to see high declines in numbers. Hence the availability of larvae or young adult and more edible Starfish is crucial to their control if the Puffer is to be of any great use.
The Marine Authority has tried many solutions, even manual eradication by divers removing Starfish. Their number are so vast though, that not much change was noticeable. It no longer supports such activities, although it will issue permits for removal by independent operators and tourism companies.
Careful monitoring and studies on the migration of Crown Of Thorns Starfish seem to be the only key to obtaining answers to future control at this point. Conserving the quality of the water and preventing these reef areas from being over fished or otherwise invaded by shell collectors will also help until a positive answer to keeping this predator under strict control is discovered. The Eco system of a coral reef can be in a state of upheaval long enough once disturbed, that new, young coral is at risk from destruction before it can reach maturity. It’s all in the timing. Will we find the answers in time?
Great Barrier Reef Marine Authority