Reef bad boy could perish as climate warms

The coral-munching crown-of-thorns starfish is a major threat to the Great Barrier Reef alongside climate change, which is warming the ocean to levels that can kill coral.

Now a new study has found climate change can also be deadly for the starfish, early in its life cycle.

James Cook University PhD student Bethan Lang has been investigating how sea temperatures affect the native marine creature for some time.

Previously, she found lots of adult starfish die when water temperatures reach 32C - a level already seen on the reef.

Now a follow-up study has shown temperatures of 30-32C can also be deadly when the starfish is in an early stage of development.

As planktonic larvae, crown-of-thorns need to attach to algae that encrusts the surface of the reef.

"The attachment process was relatively unaffected by temperatures up to 34C. It was at the next stage where rising temperatures were clearly an issue," Ms Lang says.

"The transformation of larval crown-of-thorns starfish to juveniles, and the survival of the early juveniles, were much lower at temperatures of 30 to 32C."

The algae also bleached at that temperature, making it less suitable as a base for the starfish.

Ms Lang says temperatures of 30-32C are already being recorded on the reef, and the new findings add to the mounting body of evidence suggesting warmer oceans might mean fewer, or less severe, starfish outbreaks.

And while that sounds good, there could be a sting in the tail.

"We could see a shift in the distribution of populations, with the starfish posing a greater threat to cooler, more southerly reefs."

Australian Associated Press