More than a third of corals in the Central and Northern Great Barrier Reef may now be dead due to bleaching, a new survey reveals.

The changes were noted from the north to the south regions of the Reef, which runs for about 2,300 kilometers (1,429 miles) long.

The survey results were released by the ARC Centre of Excellence for Coral Reef Studies after several months of thorough investigations made via underwater and aerial efforts.

ARC Director Professor Terry Hughes says that specifically, 35 percent of corals on 84 reefs in the said region are now dead or dying.

The situation is not entirely bad as the scientists were able to discover that some reefs are in better condition, particularly those situated from Cairns southwards. In these areas, the average death rate of corals is approximately only 5 percent.

Recurrent Problem

This is not the first time that the Great Barrier Reef has experienced such significant coral bleaching problem due to global warming. In fact, the recent dilemma is the third time in 18 years. The current situation, however, is much more notable than previous events.

Hughes says the three events have all developed while the temperatures have increased by just 1 degree Celsius above pre-industrial rates. He adds that time is running out for experts to decrease greenhouse gas emissions.

Coral Bleaching

Coral bleaching happens when unfavorable environmental events, such as changes in temperature, trigger the release of an algae called zooxanthellae. The loss of this material makes the corals turn into the color white.

The bleached corals may still regain its original color if only environmental conditions return to normal or temperatures drop. There are two possibilities if this happens: either zooxanthellae recolonize the corals or the corals succumb to death.

The Crucial Role Of Resilience

Resilience is a key factor when it comes to maximizing the natural ability of the reefs to recover hence, it is very important to boost it, says John Pandolfi, who is also from ARC Center of Excellence for Coral Reef Studies. He adds, however, that the resilience of the reef now is not as strong as it was before, especially because it had experienced three bleaching events already.

"Many coastal reefs in particular are now severely degraded," he says.

At present, the experts are looking at revisiting the same reefs in the next months to calculate the final loss of corals due to bleaching.