It's referred to as the snow storm of the Great Barrier Reef, but there's nothing frosty about the underwater romp known as coral spawning – a yearly event (this year predicted to take place between November 8 and 10) where loved-up coral release trillions of eggs and sperm into the ocean, in the hope of rejuvenating and reproducing their species.
It's the true definition of an underwater sex show, joined by other marine life, like sea cucumbers and giant clams, that help turn the ocean's blue hues to milky white.
During the months of October or November*, at the precise time when the moon is full and the water temperature is balmy, coral spawning takes place over several days, with different species spawning on different nights. Buoyant eggs sprout from the coral polyp's gut cavity and rise to the ocean's surface in a thick, soup-like layer. Once the egg has been externally fertilised, it becomes a planula larva that drifts until firmly landing on the ocean floor to mature.
A phenomenon only discovered around 35 years ago, coral spawning is an event that Cairns-based marine biologist and zoologist, Russell Hore, has only witnessed a handful of times in his 30 years of diving the Great Barrier Reef.
“From a biological point of view, coral spawning is a necessary process, and it is wonderful to see – it's the Everest of seeing reproduction in nature – but you need to be in the right spot at the right time,” said Russell.
Tidal flow is a major player in the coral courtship –too strong and the eggs are swept away – with the process relying on the ocean's current to ignite the romance. The optimal spawning time is four to six days after a full moon.
“In the lead up to the spawning day, the reef becomes fecund – it's almost as if you're watching a pregnancy on a minute scale – without the cravings for ice-cream,” said Russell.
“If you get up close, you will see little orange balls of eggs pushing to the mouth of the coral – these are little signs that ejaculation on a mass scale is about to take place.”
Divers blessed by Mother Nature to witness this burst of love may endure pungent scents and be left wading in what Russell describes as “a giant protein shake", surrounded by some greedy critters chomping away at the eggs.
“You'll find most of the fish life sitting on the sea bottom with distended stomachs, looking quite sorry for themselves. I liken it to humans stuffing themselves with Tim Tams, though it's good for their energy reserves.”
If summer conditions prevail, Russell predicts this year's spawning season will take place from November 8 to 10, or December 7 to 9 if conditions cool.
As head of the environmental division and the reef biosearch program at the Quicksilver Group in Queensland's Tropical North, Russell is passionate about showcasing mass coral spawning events on the Great Barrier Reef, which is the largest and most diverse ecosystem in the world.
“Queensland is the best place to see coral spawning – we have high speed boats to get you out to the Great Barrier Reef and highly qualified divers, many with marine biology backgrounds to guide you,” said Russell.
“November diving offers great weather – perfect warm waters and low wind.
For more information, visit www.quicksilvergroup.com.au.
Operators who offer coral spawning trips:
Adrenalin Snorkel Dive
11-17 November 2017
A five-day, four-night liveaboard experience diving or snorkelling for up to 20 people, departing from Townsville. Prices start from $1190 including meals, cabin accommodation, snorkel gear, tanks and weights for divers, reef environmental management charges and mooring fees.
7-9 November 2017
Night trips running over three days on a catamaran for snorkelers or divers, departing from the Cairns Marlin Marina. Prices start from $195 per person.
Pro Dive Cairns
A three-day, two-night liveaboard dive and snorkel with nine day and two night dives at a selection of 11 exclusive reefs. Departing from Cairns every day except Tuesday, prices start from $745 including all dive and snorkel equipment, meals accommodation, on land transfers from Cairns city and northern beaches, a guided orientation and dive insurance.