Crown-of-thorns starfish, which are predators of coral reefs and highly resistant to marine heatwaves, could proliferate
Global warming could encourage the proliferation of crown-of-thorns sea stars, which are veritable predators of coral reefs. Image: Adam Ke / Shutterstock©
Global warming is exacerbating coral bleaching. But, according to Australian scientists, it could also encourage the proliferation of crown-of-thorns starfish, which are predators of coral reefs and highly resistant to marine heatwaves.
Crown-of-thorns starfish (Acanthaster) are often referred to as corals' worst enemies. As juveniles, these starfish are herbivores. But when they reach adulthood, they become veritable predators that devour coral reefs. "The juveniles have potential for long-term persistence as herbivores as they wait for live coral to recover before becoming coral predators," explain marine biologists from Australia's University of Sydney. They tested the resistance of juvenile crown-of-thorns starfish by exposing them to heat stress scenarios designed to mimic the effect of marine heatwaves, reflecting the conditions that cause coral bleaching and mortality.
For the starfish experiments, these conditions were created using two aluminum blocks mounted in parallel to maintain stable temperatures, with hot and cold water inlets at each end. Three heat-wave scenarios were tested: 28°C, 29°C and 30°C. The control temperature was 27°C, the maximum mean summer sea surface temperature to which Acanthaster sea stars are exposed in the southern Great Barrier Reef. In the same region, the threshold for coral bleaching is 28.3°C. The starfish showed a much greater tolerance to heatwave conditions than coral, the study notes.
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