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The discovery that coral-eating starfish are early risers and feed mostly at night could help slow the decline of the Great Barrier Reef and other shallow-water corals already ravaged by global warming, scientists reported Wednesday.
Crown-of-thorns starfish suck color and life from corals, a favorite food, but in a healthy ecosystem, their numbers are kept in check.
When marine heatwaves whiten large coral swaths, however, larger fish leave the area and thorny multi-armed predators proliferate and focus on what’s left.
“Mass bleaching, crown-of-thorn starfish outbreaks and a host of other disturbances and pressures are leading to widespread coral loss and degradation of reef ecosystems,” James Professor Morgan Pratchett told AFP. Cook University.
Efforts to manually remove the ravenous starfish have largely failed, partly because they aren’t always easy to find.
But a study published in the Royal Society’s Proceedings B found a crack in their spiky armor that could help scientists buy time for the world’s coral reefs.
“Starfish appear to be sleeping and it will be harder to find them on the reef before noon,” said lead author Scott Ling, also of James Cook University.
This means they would be more active and exposed after dark, Ling said.
But the logistics of collecting them on night dives are daunting.
“We recommend concentrating dive abatement efforts from noon to early evening,” he added.
Crown of thorns starfish have a special fondness for Acropora, a species of coral that has been the basis of coral reefs around the world for the past 2 million years.
A lifeline for corals
But the main threat to coral reefs – on which half a billion people and a quarter of marine species depend – remains climate change.
Increasingly severe marine heat waves cause healthy corals to expel the algae living in their tissues, draining them of their vibrant colors in a process known as bleaching.
Half of the corals on the Great Barrier Reef have died in the past 25 years.
The remaining healthy corals are red meat, so to speak, for hungry starfish.
In the study, Ling and colleagues showed that crown-of-thorn species, such as sea urchins, feed on food and then find shelter before dawn.
If the party is close to home, they don’t wander.
But if the results are poor, they will wander up to 20 meters and then find their way back, a pattern known as homing behavior.
“Saving coral reefs requires major changes not only in management actions on the ground, but also concerted efforts to reduce greenhouse gas emissions,” Pratchett said.
The United Nations Climate Science Advisory Committee, the IPCC, found that 1.5 degrees Celsius (34.7 degrees Fahrenheit) of atmospheric warming above pre-industrial levels would doom 90% of the shallow-water corals in the world. world.
An increase of 2 degrees C would mean their almost complete disappearance.
The loss of coral reefs around the world would double the damage caused by coastal flooding and triple the destruction caused by storm surges, according to a study last year.
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