Crown-of-Thorns Sea Star - Friend or Foe?

What is it?

- second largest sea star in the world, next to the Giant Sunstar
- considered a serious threat to the Great Barrier Reef
- found in Red Sea, Indian Ocean, Pacific Ocean
- an Echinoderm – an invertebrate with spiny skin
- spines on it’s skin contain venom
- like all sea stars, can regenerate parts of its body if the part is removed – I wish humans had that ability!

What does it eat?

- nocturnal sea star that feeds on reef coral polyps
- crawls over coral and extends its stomach out if its body and absorbs the coral using digestive enzymes

Who eats it?

- Giant Triton snail and the Harlequin Shrimp, some large reef fish
- The larvae is planktonic, so the population is mainly controlled by predation of the plankton

Why is it a threat?

- overpopulation has led to reef destruction
- voracious appetite – can devour a 6mx6m area of living coral per year
- decline in predator population - Triton snail is collected for its beautiful large shell

Other threats to the reef:

- overfishing, land-based pollution, coral bleaching, increased sea temperatures (global warming)
- agricultural runoff creates algal blooms, giving Crown of Thorns larvae an alternative food source

So what’s good about it?

- when kept in reasonable numbers is important for maintaining biodiversity - natural succession of the reef can occur when fast growing coral are prevented from overpowering the slower growing coral