One hundred kilometres off the central Queensland coast, at the southern end of the Great Barrier Reef, lies a tiny island paradise.
One Tree Island is a research mecca, a transient home to just a handful of scientists who have dedicated their lives to saving this wonder of the world.
One Tree Island is 100 kilometres off the central Queensland coast. (Supplied: Heinrich Breuer)
Associate Professor of marine biology Will Figueira is among those permitted to visit the island, and has been conducting research there for more than two decades.
As he puts on his wetsuit and readies himself to dive into the pristine waters, he has one thing on his mind — how much of this coral will be dead?
Will Figueira has been working on One Tree Island for two decades. (ABC News: Scout Wallen)
The researchers are tracking the impact of last summer's coral bleaching event. (ABC News: Scout Wallen)
Professor Figueira and his team of researchers from the University of Sydney have been tracking the impact of last summer's coral bleaching event.
One Tree Island is 100km off the central Queensland coast.
"I hate to say I am getting numb to it, but we kind of expected it," Professor Figueira said.
One Tree Island is one of only two 'Orange Zones' on the reef, meaning it is only accessible for research and education purposes.
One Tree Island can only be accessed for research purposes. (ABC News: Scout Wallen)
Professor Figueira says that makes it an optimal location for conducting research, as there are no tourists or other factors to influence the coral's health.
The only impact comes from water temperatures.
"You're so far out from everything, which is what makes it so special … it is hard to get to, and therefore [other factors have] low impact," he said.
The island has a large lagoon that wraps around the north-western end and acts as a Petri dish of coral and sea life.
The lagoon off One Tree Island. (Supplied: Heinrich Breuer)
Fragile cardinalfish swim among porites in the lagoon (Supplied: John Turnbull, University of Sydney)
Professor Figueira said his most recent research had raised concerns.
"We get a little bleaching every summer because it gets quite warm in the lagoon, but nothing as widespread as we saw, unfortunately, this last year," he said.
"I think this will be a pretty big change for the lagoon … nothing like it's seen, certainly in the last 20 years."
Dead coral at One Tree Island. (ABC News: Scout Wallen )
Last summer's bleaching event
The reef was decimated in the bleaching event in January, when water temperatures that usually don't top 28 degrees, sat on 29 degrees for the entire month.
"It would have been 30 to 31 degrees inside the reef, which is just way too warm for the corals down here," Professor Figueira said.
Large sections of the reef have suffered bleaching. (Supplied: John Turnbull, University of Sydney)
In February, the team of researchers witnessed the widespread fluorescence of dying coral.
Coral can turn fluorescent in the bleaching process. (Supplied: John Turnbull, University of Sydney)
When they returned in April, the coral was bleached white, meaning it was under enormous stress.
"There was a lot of death already," he said.
Many corals died when water temperatures remained high last summer. (Supplied: John Turnbull, University of Sydney)
Now the team is back to assess the damage again.
"There are some signs of recovery, but there's quite a few groups [of coral] that are dead and covered in algae," he said.
"I am sure that the mortality number of things that did bleach is going to be up to 50 per cent, hopefully not higher."
Isabelle Marrable is part of the research team. (ABC News: Jasmine Hines)
Isabella Marrable, a PhD candidate at the University of Sydney, described the condition of the reef as "shocking".
"It was a sobering experience to be out there and see the extent of this year's bleaching event," she said.
She said although she was expecting to see significant damage, "there is always that part of you that hopes that maybe this time it'll be different".
A bleached anemone on One Tree Island. (Supplied: John Turnbull, University of Sydney)
Professor Figuiera said for the reef to have a chance of even partial recovery, normal summer temperatures this year would help.
"It doesn't have to be exceptionally cool, just not hot," he said.
But unfortunately, the forecast is not good.
Bleached, fluorescing and dead algae-encrusted coral outside the lagoon. (Supplied: John Turnbull, University of Sydney )
According to the Bureau of Meterology's summer outlook, the long-range forecast for November to January shows another hot summer ahead.
Days are predicted to be warmer than average across the country, and unusually high minimum temperatures at night are likely for the eastern states.
3D mapping of the reef
For a decade, Professor Figueira and a team of scientists have been using the unique oasis on One Tree Island to create 3D maps of the reef.
The team use these cameras to map the reef. (Supplied: John Turnbull, University of Sydney)
The cameras take hundreds of photos to create 3D maps. (Supplied: Heinrich Breuer)
"You just take thousands and thousands of highly overlapping pictures and use some sort of fancy software to stitch them all together," he explained.
He said the process had been helpful in documenting the impact of the bleaching.
3D map of a One Tree Island reef. (Supplied: John Turnbull, University of Sydney)
"We can look, zoom right in and we can track the colonies through time … and their fate through this bleaching event," he said.
Professor Figueira said the reef potentially could recover but back-to-back bleaching events were making it extremely challenging.
He said it would be several months before his team collated all the data on the rate of bleaching and mortality on the reef uncovered in this most recent trip.
The researchers will return to One Tree Island in February 2025.
Reefs near One Tree Island. (Supplied: Heinrich Breuer)