Scientists have confirmed rising sea temperatures are having a greater impact on the Great Barrier Reef than first thought.
Branching corals that act as a nursery for juvenile marine life and give the World Heritage-listed icon its three dimensional aspect experienced a catastrophic die-off following bleaching in 2016, a new study shows.
"We saw some corals rapidly dying," said Dr Scott Heron, one of the study's authors.
"Bleaching... is essentially a starvation process that occurs over one to two months. This rapid onset is not the same starvation mechanism. The best way to describe it is akin to cooking," he said.
An aerial view of the Great Barrier Reef. Source: Getty
The paper, published in the scientific journal Nature, details how that particular marine heatwave has sparked a radical shift in the composition of the reef.
It means large swaths of mature and diverse clusters have been transformed into a degraded reef structure, Queensland coral reef scientist Professor Terry Hughes says.
"We've been saying for a long time that these bleaching events are going to get more frequent and the consequence of that will be that the mix of species will change," Professor Hughes said.
"(But) there's a big difference between making a prediction and then measuring it come to pass."
In years to come, sprawling and intricately shaped coral species such as the Staghorn variety will be largely replaced by flat, mound-shaped formations.
"Overall we'll probably have less coral and overall we'll have less biodiversity," Professor Hughes added.
The paper repeated previous science suggesting parts of the reef may never recover from the 2016 bleaching, and again called for more urgent action to prevent its decline as a result of climate change.
Whether or not targets such as those set out in the Paris climate agreement are met, Professor Hughes said a major transition in the reef's appearance was already well underway.
This image shows the Great Barrier Reef suffering mass bleaching for a second year in a row at Vlassoff Cay, near Cairns, 2017. Source: AAP
Responding to questions about the study on Wednesday, Queensland Premier Annastacia Palaszczuk said her government would continue to fund measures to protect what she described as one the state's greatest natural assets.
A Deloitte Access Economics report in June valued the reef at $56 billion, underpinning 64,000 direct and indirect jobs, which contributed $6.4 billion to Australia's national economy each year.
It warned of the vast economic consequences for Australia unless more is done to protect the reef.
