What is the keystone species of great barrier reef?

The keystone species of the Great Barrier Reef is undoubtedly the crown-of-thorns starfish (Acanthaster planci). This large, starfish preys on hard corals and can cause significant damage to the reef ecosystem if its population becomes too large. When the crown-of-thorns starfish population is in check, the reef is able to thrive and maintain its biodiversity. However, when the starfish population increases rapidly, it can cause extensive coral damage and lead to the degradation of the reef. Therefore, managing and controlling the crown-of-thorns starfish population is crucial for the long-term conservation and health of the Great Barrier Reef.