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Over the past 30 years, Australia’s Great Barrier Reef has experienced a 50 percent loss in coral. Though part of the decline is being attributed to the warmer ocean temperatures caused by climate change, about half of the damage is due to the proliferation of the crown-of-thorns starfish (COTS). The deadly predators can devour as much as 53 square feet (five square meters) of live coral annually.
Native to the region, the starfish — which grow as big as 32 inches across, have over 21 arms, and are covered in venomous thorn-like spikes — are beneficial in small numbers. They help keep faster-growing coral reef in control, allowing slower growing colonies to form. However, the recent population explosion, combined with two consecutive years of coral bleaching, is destroying the reef at an unprecedented rate.
The starfish population is currently being controlled with bile salt solutions or ordinary household vinegar. However, this is a tedious process that requires dive teams to inject each specimen individually. Now, Australian marine scientists are hoping to get some help from a natural COTS predator – the Pacific or giant triton, snail. Named after the Greek god Triton — son of Poseidon and god of the sea — it is one of the world’s largest sea snails, reaching lengths of up to two feet! The marine gastropods are so good at hunting down the starfish that even their scent is enough to send the sea stars scampering. Unfortunately, the endangered giant tritons, which have been hunted down for their beautiful shells, are hard to find. Also, since they only consume a few starfish a week, it would take an army of snails to make a difference.
To try to increase the snails’ numbers by breeding them in captivity, researchers from the Australian Institute of Marine Sciences went in search of them. It took them two years to find just eight specimens, but the effort was worth it given that over the past month, they have produced over 100,000 tiny larvae. The researchers hope to learn more about the lifecycle of these elusive marine creatures as they grow and release them once they are old enough to prey on the COTS. Cherie Motti, leader of the triton breeding program, says, "If we can have a natural predator doing the job for us [killing the starfish], it will be the best outcome." Hopefully, the researchers will be successful in their endeavor.
Besides creating thousands of jobs and adding over $50 billion to the country’s economy, the Great Barrier Reef is also crucial to the local ecosystem. As you may know, the brightly colored calcium carbonate structures are a symbiosis, or partnership, between coral polyps and zooxanthellae. The polyps provide a home for the single-celled organisms in exchange for food and the vivid color we have come to love. In addition to sheltering the zooxanthellae, the strong corals help protect the shoreline from storms and floods. The polyps, which use calcium ions and dissolved carbon dioxide to form the calcium carbonate skeletons, also help reduce the level of the toxic gas in the oceans. Hence, it is imperative to do all we can to save these delicate structures.
Resources: aims.gov.au, earthtouchnews.com,phys.org.