A capacity building program for coral has been hailed a success by scientists on the Great Barrier Reef during its annual spawning event.
Over two nights on the Queensland coastline, scientists and tourism operators gathered on the water in the darkness to observe the annual coral spawn phenomenon, which is triggered by a full moon and warm water temperatures.
Perfect conditions met groups on the first evening before thunderstorms and a deluge hampered work on their second night on the water.
"All the crews out there got stuck under a bit of a thunderstorm for a while," pilot deployments program director Mark Gibbs told AAP.
"There was quite a bit of coral around but there was a big deluge coming out of the sky at the same time, which is kind of fun."
Described by British broadcaster and biologist Sir David Attenborough as "one of the greatest of all natural spectacles", trillions of eggs and sperm were released into the ocean in what scientists describe as an underwater snowstorm.
These will fertilise and form larvae that float in the ocean for about a week.
"Absolutely (it was a success)," Dr Gibbs said.
"There's been a been a lot of bleaching - what happens is the corals often don't have the energy to reproduce.
"There seemed to be enough that we're OK - that we got a pretty strong response the last couple of nights."
Trillions of eggs and sperm are released into the ocean in what is known as an underwater snowstorm. (HANDOUT/CALYPSO PRODUCTIONS)
If the larvae land directly above a coral reef they settle and small portions develop into new corals.
However, the odds of coral larvae surviving are challenging.
Only one in a million naturally find their way back to the reef, with most swept away by currents or eaten by predators.
So overnight, scientists, traditional owners and local tourism operators joined forces to increase the odds.
They utilised a cutting-edge restoration technique called Coral IVF in the biggest single reef restoration effort in the world.
The process involves capturing coral spawn in floating nursery pools, increasing fertilisation rates 100-fold, and releasing them over the top of coral in need of new growth.
This takes the odds of one in a million larvae surviving to about one in 10,000.
The Great Barrier Reef faces unprecedented stress due to climate change. (HANDOUT/CALYPSO PRODUCTIONS)
Stretching more than 2000km and comprising about 3000 individual reefs, the conservation work on the Great Barrier Reef comes as it faces unprecedented stress due to climate change.
In nature, the event is highly complex and synchronised as there are various species of coral in the reef and they're not meant to cross-breed.
"Spawning takes place over three to four nights with different species of coral spawning on different nights," Great Barrier Reef Foundation coral reef restoration director Melissa Rodgers told AAP.
The collaborative approach to Coral IVF was piloted in the Whitsundays during the past four years and expanded to Cairns and Port Douglas for the first time in 2024.
The technique was initially developed by Australian scientist Peter Harrison while working in the Philippines and has been adapted for use around the world.
"This is a capacity-building program," Dr Gibbs said.
"We're working with traditional owners, lots of marine tourism operators, marine contractors, to train them how to do these at-scale interventions where we're putting very large numbers of corals back into the system."