Great Barrier Reef: how a spectacular coral spawning event is helping to breed heat-tolerant corals | Great Barrier Reef

It’s nearing 10pm, and Dr Kate Quigley is nonetheless ready. Utilizing purple lights to minimise disruption to the animals’ behaviour, she is inspecting corals.

Quigley, who research reef restoration on the Australian Institute of Marine Science, is on the lookout for “little purple dots all around the floor”. A pimply look is a hallmark signal that a coral is about to spawn, releasing sperm and eggs in bundles resembling small bubbles.

Relying on the species, they are often vivid pink, purple or blue. “It’s nearly like shaking a kind of snow globes,” Quigley says. “You see all of the little particles within the water.”

Dr Kate Quigley
Dr Kate Quigley on the lookout for ‘little purple dots’, a signal that a coral is about to spawn. {Photograph}: Marie Roman/AIMS

Quigley is working at AIMS’s Nationwide Sea Simulator, a huge facility in Townsville the place greater than 3m litres of filtered seawater is pumped by day by day, housing large numbers of coral colonies. On the SeaSim, because it is identified, buzzing tanks are calibrated at particular temperatures and partial pressures of carbon dioxide – the latter for experiments on ocean acidification.


Coral spawning, which happens en masse as soon as a 12 months, is one in every of Earth’s nice organic spectacles. Quigley likens the size and grandeur of it to the annual mammal migrations in Africa.

Up and down the Great Barrier Reef, for a number of days after the November full moon (this 12 months on 19 November), a number of species of corals synchronise the discharge of their sperm and eggs. Out within the ocean, billions of those bundles float to the water’s floor, fertilise and become larvae that ultimately choose the reef and kind new coral colonies.

Researchers hope to breed Great Barrier Reef corals more resilient to extreme heat events – video
Researchers hope to breed Great Barrier Reef corals extra resilient to excessive warmth occasions – video

The corals housed on the SeaSim spawn in captivity concurrently they do within the wild. For a number of consecutive days this week, Quigley and her colleagues have labored late into the evening, rigorously gathering spawn bundles for a selective breeding program.

Every spawning coral is saved in its personal separate container, so its bundles may be remoted. Many are housed in outside tanks, below the moonlight, which is an vital cue that triggers the spawning event. For corals saved indoors, the SeaSim has finely calibrated services that permit scientists to replicate each the timing and depth of each daylight and moonlight.

A researcher at the Australian Institute of Marine Science coral spawning facility
A researcher on the Australian Institute of Marine Science coral spawning facility. {Photograph}: Roslyn Budd/AIMS

“We’re now in a position … to replicate these pure alerts that the corals would wish,” Quigley says. She and her group collected tons of of the spawning corals solely within the final fortnight. Leaving the marine invertebrates of their pure environments for so long as doable additionally maximises their publicity to cues for spawning they’d get within the wild, which incorporates a fast rise in temperature round this time of 12 months.

Breeding for warmth resilience

The Great Barrier Reef includes greater than 3,000 particular person reefs, a patchwork of marine life roughly the scale of Italy. There is a pure temperature gradient from north to south: the waters within the northern a part of the reef, nearer to the equator, are hotter.

“These corals up [north] are higher in a position – simply by the publicity that they’ve had over their lifetime – at withstanding excessive temperatures,” Quigley says. “Within the southern Great Barrier Reef, it’s colder down there, so when [corals] get hit by a heatwave, they’re way more susceptible.”

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Pure variations in warmth tolerance types the premise of Quigley’s selective breeding analysis. Late final 12 months, she developed a machine studying algorithm that produces GPS coordinates indicating the place essentially the most heat-resilient corals may be.

Final week, she and her group returned from an expedition to the far northern Great Barrier Reef, 875km away from the SeaSim. Utilizing her algorithm, they collected tons of of probably heat-resilient corals, which had survived the excessive temperatures of the 2016, 2017 and 2020 mass bleaching occasions.

A researcher collects coral in at Wood and Martin reefs
A researcher collects coral in at Wooden and Martin reefs for spawning on the Nationwide Sea Simulator. {Photograph}: Marie Roman/AIMS
Broodstock collection in Far North Queensland
Broodstock assortment in far north Queensland. {Photograph}: Marie Roman/AIMS

After the spawning within the SeaSim, the scientists will breed the heat-hardier corals with extra susceptible specimens collected from the southern Great Barrier Reef. The method of blending spawn is “not dissimilar to mixing cocktails in particular proportions”, Quigley says. “We are able to management who the mum is and who the dad is … we’re in a position to create child corals which have a combination of those genetics.”

The analysis hastens a pure course of known as gene move. Analysis exhibits that corals’ genetic materials, together with heat-adaptive genes, spreads naturally throughout the reef. “There is motion of genes,” Quigley says. “Nonetheless, it’s most likely going to occur too sluggish for the form of fee of warming that we’re getting now.”

Accelerating the unfold of genetic materials is one in every of a number of methods being explored to assist make the reef extra resilient, says Dr Line Bay, who leads the reef restoration, adaptation and restoration group at AIMS.


Corals stay in symbiosis with microscopic algae, which play an vital position of their development and survival. “We’ve a number of initiatives which might be how these algae have an effect on the well being of corals and whether or not we are able to affect … the warmth tolerance of corals by direct number of the algae,” Bay says.

Local weather change ‘a very important risk’

Within the SeaSim, tank temperatures may be dialled up to check how nicely corals – both these which might be selectively bred, or which have heat-tolerant algae – may stand up to the warmth of bleaching occasions.

The Intergovernmental Panel on Local weather Change report initiatives that below 2C of world warming, 99% of coral reefs will decline. “As we transfer into the long run, we all know that the water is going to heat, not solely a lot, a lot hotter, but additionally a lot quicker,” Quigley says.

For the primary time this 12 months, the group is hoping to selectively breed a species of Porites coral – huge, slow-growing corals that resemble boulders. If profitable, it is going to be the sixth species included in this system.

Broodstock collection in Far North Queensland
The primary precedence for saving the reef is to curb carbon emissions, scientists say. {Photograph}: Marie Roman/AIMS

The Great Barrier Reef accommodates round 400 completely different species of coral, estimates Prof Terry Hughes, an internationally famend coral reef scientist at James Prepare dinner College.

The AIMS analysis sheds gentle on the traits of untamed corals following current bleaching occasions, Hughes says. “It tells us about their warmth tolerance, it tells us whether or not that warmth tolerance is shifting.

“We additionally get badly wanted info on how the Barrier Reef is wired when it comes to motion of larvae from one place to one other – gene move.”

Hughes, who directs the ARC Centre of Excellence for Coral Reef Research, says a hurdle for coral restoration initiatives is the massive scales they need to work on to have an effect.

“In the event you needed to enhance coral cowl [on the Great Barrier Reef] … by 1%, you’d want 250m massive corals,” he says. That may contain rearing fast-growing coral species for round 5 years to get them to the scale of a dinner plate. “As a pathway in the direction of intervention, scale will at all times be the most important problem.”

Bay emphasises that reef restoration “is no silver bullet. Local weather change is a very important risk to coral reefs and we want robust motion on local weather change to give ourselves the perfect likelihood of survival into the long run,” she says.

Quigley agrees. “When you consider the size of the ecosystems which might be being impacted, just like the Amazon, just like the Great Barrier Reef – these are large, advanced ecosystems that individuals have been finding out for a very long time, however we’re simply scratching the floor when it comes to understanding essentially how they function.”

The primary precedence for saving the reef is to curb carbon emissions, Quigley says. Administration practices, corresponding to regulation of water high quality, packages to take away crown-of-thorns starfish, and managing fisheries, will even assist to alleviate stress on the ecosystem.

“After which third, we are able to have a look at these modern restoration ideas,” she says. “We are able to begin to assume … what sort of restoration can we develop now, whereas there’s nonetheless time.”

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