Starfish turning into carnivorous predators by devouring coral reefs

By Ellie McDonald via SWNS

Starfish are transforming into carnivorous predators and devouring coral reefs, reveals new research.

Marine biologists found juvenile crown-of-thorns starfish can withstand heatwaves well above the level that normally kill coral, and then turn into predators that devour reefs as they begin to grow back.

The new findings suggest the species’ resilience to warming waters could exacerbate the effect climate change has on coral reefs, with a single adult starfish eating between 15-30 square meters of coral a day.

They are classified as a species of concern because the damage large population’s can cause to coral is more significant than any other species - they fall behind only cyclones and bleaching events in their impact on coral destruction.

Study co-author Matt Clements, a PhD student at the University of Sydney in Australia, said: “Loss of natural predators due to overfishing and the build-up of nutrients in the water have been suspected to contribute to outbreaks of crown-of-thorns starfish.

“Now we have evidence that bleaching induced coral mortality could aid the seafloor-dwelling juveniles, leading to subsequent large waves of adults in reefs which exacerbate the ravages of climate change.”

The study, published in the journal Global Change Biology, found that juvenile crown-of-thorns displayed a surprisingly high heat tolerance, higher than that observed in their adult counterparts.

This means that, even if the coral-eating adult stage declines in climate change-driven ocean warming scenarios, perhaps from a lack of their coral prey or from the heat, their herbivorous young can wait patiently for the opportune moment to grow into carnivores.

Considered one of nature’s ultimate oral predators, crown-of-thorns starfish are native to the Great Barrier Reef and found in the Indo-Pacific region.

During outbreaks of their carnivorous adult phase, the starfish dine pervasively on stony coral, leaving lifeless skeletons across the reef. These skeletons eventually become home to algae before crumbling.

The researchers also identified factors that contribute to the juveniles’ ability to survive in warming conditions. They include small size, which may reduce physiological requirements, and their ability to feed on a variety of food sources, despite preferring a diet of coralline algae.