It occurs when the mood’s right and the moon is at its fullest; one of nature’s most remarkable reproductive spectacles in which corals across the Great Barrier Reef shed their inhibitions and partake in their annual mass, synchronised public display of affection.

This is the mass coral spawning – the moment in time when new life is brought to the Great Barrier Reef, as corals release bundles of sperm and eggs ‘in their millions’ into the ocean in what experts and observers each year describe as a “spectacle of colour”.

But those experts have begun to notice something rather more “magical”. And anticipation is building for this season’s big spawning occasion. Because this isn’t a party exclusive to corals – the doors to this ‘reproductive spectacle’ are being flung open to invertebrates and sponges, too.

The mass coral spawning of the Great Barrier Reef is something that has been witnessed by experts for the past 40 years. What is now emerging, however, is just how many other species of marine life are piggy-backing on the event, and taking full advantage of the moment to have a little fun of their own. A showcase, say scientists, of “the resilience and regenerative powers” of the Barrier Reef ecosystem.

“It’s one of nature’s most remarkable reproductive spectacles, with invertebrates and sponges often spawning at the same time as the coral,” said the Great Barrier Reef Marine Park Authority’s chief scientist, Dr Roger Beeden. “We’ve known about mass coral spawning for more than 40 years, but we’re only now discovering all these other marine species are taking advantage of the coral spawning cover to have a little fun of their own.”

It’s apparently a safety in numbers approach. By the cover of the coral’s mass spawning, Dr Beeden and Great Barrier Reef researchers are finding that marine species such as clams, sponges, sea cucumbers, and starfish (among others) are using the protection of this unique breeding opportunity to release their own spawn and create their next generations.

As you’d expect, the mood has to be just right. But forget the Barry White records and good luck with the candles, because this magical event will only occur after a full moon and only when the water temperatures are right – enough to stimulate the maturation of reproductive cells within adult corals.

Hit all those crucial elements and the scene will be perfectly set for a mass spawning event which, according to reef experts, can last anywhere between a few days to a week.  

Of course, it’s a little more orderly than all that, spawning won’t occur across the entire reef at exactly the same time. Rather, corals on inshore reefs will usually spawn after the first full moon in October, while those on outer reefs tend to spawn during November, sometimes even December. But the process will be the same: During spawning, entire colonies of coral polyps will release eggs and sperm into the water for mass fertilisation, simultaneously, creating an effect that has been likened by witnesses to a “snowstorm”. 

Once a released sperm has fertilised its egg, a tiny, free-swimming larvae called planulae will develop. This planulae will, eventually, settle on the reef substrate, where it will grow into new coral colonies. these events are critical to the regeneration of coral ecosystems as it is a fundamental part of repopulating the reefs.

Given the current health of coral ecosystems around the world – suffering, as they are, the fourth and most impactful mass bleaching event, right now – this mass spawning is more than just “an amazing sight” but a vital moment for reef renewal in the face of another forecast for a hot summer.

“Coral spawning is an incredibly important part of the natural recovery process. There is no more important event for the future of the reef than the maturation of reproductive cells within adult coral,” said Dr Beeden. 

“These spawning corals are genetic gold for reef resilience. Corals that have survived coral bleaching events may pass on more heat tolerant genes to the next generation enhancing the adaptation of coral communities and long-term survival of the reef.”

In its role as steward of the Great Barrier Reef marine ecosystem within Australian waters, the Great Barrier Reef Marine Park Authority has said that “coral spawning is a time of new life and hope – a time to renew our commitment to taking small steps every day to reduce the impact of climate change, helping ensure the health of the reef, both now and into the future.”

And if you’re a coral polyp – it sounds like one heck of a full moon party.

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