Crown-of-thorns starfish, Acanthaster planci, are voracious predators of hard coral polyps. They evert their stomachs directly onto their prey and digest the tissues off the coral’s calcareous skeleton.
This echinoderm species inhabits coral reefs in the Red Sea and Indo-Pacific ocean. It is the world’s second largest species of sea star.
The starfish are named for their striking and prominent arrangement of large venomous spines that contain a neurotoxin.
These corallivores can have a devastating effect on reefs, particularly if already under pressure from other factors such as disease and bleaching.
After a starfish has fed on a coral, it leaves a white patch behind as the coral’s symbiotic zooxanthellae, which are responsible for their hosts’ colors, have been consumed. Watch the starfish in action in this video.
Some scientists believe the starfish help maintain reef diversity by preventing fast-growing coral species from dominating reefs. However, the starfish’s population sizes seem to have been increasing since the 1970’s and many divers carry out control measures such as a deadly injection of sodium bisulfate.
Pulau Weh lies at the most north westerly tip of Indonesia, where the Indian Ocean meets the Andaman Sea. The deep water and strong currents that sweep past the island provide perfect conditions for both large and small marine species.
The island has active volcanic vents that emit sulfurous gases and lies close to an active subduction zone.
Pulau Weh lies just off shore from Banda Aceh, the city that was devastated during the 2004 tsunami. Fortunately, damage on the island was minimal compared to the devestation on the mainland.
Matthew Oldfield is a freelance photographer based in Bali, Indonesia, specializing in editorial and documentary images from both above and below the waves. He works primarily with charities, NGO’s, and other organizations working to conserve the environment, endangered species, and disappearing cultures.
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