Australian marine scientists are racing against time to collect data as coral spawns on the Great Barrier Reef, simultaneously mating and birthing.
The spawning gives scientists a very narrow window of opportunity to gather the samples they need for research to help the Great Barrier Reef recover from bleaching.
Dr Line Bay, a senior research scientist at the Australian Institute of Marine Science (AIMS), said it was the most important day on the calendar for researchers.
"Individual coral species tend to have a certain time when they will spawn, so we have our team ready to collect the spawn when it happens.
"Then we can actually separate the eggs and the sperm, and we can cross them and produce these new families of corals that we can then rear in the lab."
The process is sparked by warm summer water temperatures and the full moon, and usually happens only once a year.
But experts said there was likely to be a split spawn this year which could see coral colonies spawn again after the December full moon.
Corals spawn at night and are sensitive to bright light, so scientists studying corals at the National Sea Simulator, at the AIMS Cape Ferguson headquarters near Townsville, will work through the night to monitor and collect samples.
They will use only red lights around the corals to avoid disturbing them, collecting samples for experiments.
AIMS chief executive Paul Hardisty said the institute's sea simulator was the world's largest and most advanced scientific research aquarium.
"We have tonnes of scientists and camera crews down here to watch this incredible miracle - which is even more important now perhaps than it has ever been at any point in history with the recent loss of so much of the reef," he said.
"What it allows us to do is to change the conditions, to simulate any possible future conditions, so we can immediately and in real time and to a very high degree of accuracy, change temperature, salinity, pH.
"We can add various contaminants to waters, we can simulate dredge plumes, we can simulate introductions of various chemicals and so on, and we can literally see how corals respond under these future scenarios."
Their experiments will explore why some coral individuals or species are more tolerant to warming than others.
Dr Bay said the findings could play a vital role in managing coral populations into the future.
"We're trying to trial ways we can help coral become more tolerant in the future. We don't know what the future is going to bring but it's very likely the future is going to be more stressful than it already is," she said.
A recent report by Deloitte Access Economics, commissioned by the Great Barrier Reef Foundation, found the reef contributed $6.4 billion to the Australian economy, but Mr Hardisty said the reef was far more valuable than the report suggested.
"It provides a major protection for the coastline, for these thousands of kilometres of coastlines for storms and so on, without the reefs there the storms would be much more damaging than they are. So that can be translated as damage to property and so on."
And although the reef has been hit hard in two back-to-back bleaching events since 2016, Mr Hardisty said where there was life, there was hope.
"And there's lots of life out there and that's what we need to focus on," he said.
"The reef is battered, bruised, but still beautiful and incredibly valuable."