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A successful spawning event has given scientists hope that the Great Barrier Reef can recover from coral bleaching.
The project, which is led by the Australian Institute of Marine Science (AIMS), took place after the recent full moon and is focused on heat-tolerant corals with a goal to help them resist bleaching in the future.
AIMS research scientist Dr Kate Quigley said: "The far north of the Reef has corals that have survived some of the most devastating coral bleaching events.
The Woppaburra corals made it to the party, but it seems we may party on a few more nights in the @SeaSim_AIMS @aims_gov_au! We still have a few species left to go! #KICP #Spawnathon2021 pic.twitter.com/BWRpA7nUtg
- Carly Randall (@DrCarlyRandall) November 28, 2021
"These corals have the potential to withstand higher temperatures than those from other reefs.
"We aim to harness this natural heat tolerance and facilitate its introduction to more vulnerable populations, so we can speed up the natural process of adaptation.
"This could help the Reef keep pace with rising temperatures, in hope of giving corals a fighting chance against future bleaching."
AIMS' National Sea Simulator, a facility in Townsville which hosts more than three million litres of seawater and houses a huge number of coral colonies, allowed the scientists to monitor the annual spawning event that takes place across several days.
The acroporids always know how to put on a show under the red light! The spawning continues on night 6 as we fill the nursery with growing embryos for experimental field deployments @SeaSim_AIMS @aims_gov_au #ReefTrust #spawnathon2021 pic.twitter.com/utfhIhcm4j
- Carly Randall (@DrCarlyRandall) November 25, 2021
All across the Great Barrier Reef, multiple species of coral synchronise during the event to release their sperm and eggs.
These bundles then float to the surface, fertilise and develop into larvae which will form new coral colonies.
The simulator, known as SeaSim, helps Quigley and her colleagues selectively breed coral that can withstand rising temperatures.
The Great Barrier Reef is made up of more than 3,000 individual reefs with a natural gradient in temperature from north to south.
The coral in the south is more sensitive to increasing water temperatures and scientists are working to identify varieties of coral that have previously withstood the bleaching.
Over 50 colonies from seven species spawned last night - and it's on again tonight!@SeaSim_AIMS has over 40 researchers and staff onsite, working late into the night on 25 projects to help coral reefs survive climate change.https://t.co/ioQTW9NbLl#Spawnathon2021 pic.twitter.com/lcbfue6xNb
- Australian Institute of Marine Science (@aims_gov_au) November 24, 2021
Coral bleaching occurs when corals are under stress, such as in extreme temperature changes.
The corals expel the microscopic algae that live in their tissues which makes them transparent, exposing their white skeleton. Bleached corals are not dead, but are more at risk of starvation and disease.
A temperature increase of just one degree Celsius for only four weeks can trigger bleaching. Climate change is causing temperature changes which are drastically impacting the Great Barrier Reef.
In previous years, the AIMS team has successfully spawned and mixed five different coral species - including fast-growing branching and encrusting varieties.
This year's collection also includes the massive, slow-growing boulder corals (Porites), which is the sixth coral species the team will attempt to selectively breed.
"Working with Porites is challenging," Quigley said. "It's hard to identify them because of their small polyp sizes and determine who is male and who is female. Then we need to find a sufficient number of these colonies.
First night of Porites eggs, fingers crossed for more tomorrow from all our reefs. Hyacinthus looking good! @aims_gov_au @SeaSim_AIMS #Spawnathon2021 pic.twitter.com/JzWxeIsNmC
- Dr. Kate Quigley (@la__cientifica) November 23, 2021
"Working with these species is essential to understand a reef's ability to recover after disturbance, given their different ecological roles. For example, Porites is a very long-living coral that forms an important part of the physical structure of coral reefs."
Reef Teach marine scientist Gareth Phillips, 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. I think we must all focus on the victories as we emerge from the pandemic."