The event was recorded by scientists on November 23, off the coast of Cairns, Queensland, when the world-famous coral began “birthing” billions of offspring, casting sperm and eggs into the Pacific Ocean. The event sees the coral erupt with colour over the course of two or three days.
Although it takes place every year, it is especially reassuring for scientists given the damage to the reef in recent years.
The coral bleaching was triggered by unusually warm water temperatures in recent years, particularly in 2016, 2017 and 2020.
The warmer temperatures have caused damage to two-thirds of the coral in the reef network, which spans 134,000 square miles.
A study published last year found the Great Barrier Reef had lost 50 percent of its coral populations in just three decades, with climate change being a key driver of reef disturbance.
Meanwhile, researchers from Queensland’s ARC Centre of Excellence for Coral Reef Studies (CoralCoE) discovered that almost all small, medium and large corals had been depleted between the years 1995 and 2017, in a study examining coral communities and colony sizes within the reef.
Reef Teach marine scientist Gareph Philips, who is studying the spawning event as part of a wider project monitoring the health of the reef, said: “It is gratifying to see the reef give birth.
“It’s a strong demonstration that its ecological functions are intact and working after being in a recovery phase for more than 18 months.
“The reef has gone through its own troubles like we all have, but it can still respond – and that gives us hope.
A recent study published by James Cook University’s Prof Terry Hughes and colleagues found only 1.7 percent of individual reefs had avoided bleaching.
Almost all of the places that escaped damage were in an area known as Swain reefs in the southern section of the world heritage listed marine park.
Some reef experts hoped that cooler areas would act as refuges from bleaching, enabling corals to survive and naturally disperse their larvae onto damaged reefs.
However, the research found that many areas “earmarked earlier as candidate refuges” had now experienced severe or moderate bleaching at least once.
Mr Hughes said: “The world is now littered with former potential coral reef refuges that have since bleached.”