Despite this worrying event, the state of the reefs in this area are currently deemed to be "good".
Coral is an umbrella term for several species of marine invertebrates (animals without backbones). They have a hard outer layer (exoskeleton) made from calcium carbonate - the same stuff shells are made out of.
They are found all over the globe, from tropical waters to the freezing polar regions. However, corals only form reefs in the warm, shallow seas of the tropics. The most famous of these is the 2,300km-long Great Barrier Reef, located off the north-eastern shores of Australia.
Healthy coral forms a symbiotic relationship with microscopic algae, known as zooxanthellae. In return for being allowed to live in the corals' hard, calcium carbonate exoskeleton, the algae help produce food for their hosts. Zooxanthellae also provide the vibrant colours we associate with healthy coral reefs.
However, as the waters warm, and the delicate marine ecosystem becomes sick, or stressed, the mutually beneficial relationship breaks down.
The algae "jump ship", leaving the coral without its main food source. The result is that the coral turns white or very pale and becomes more vulnerable to pathogens.
Coral bleaching is thus a visible and dramatic signal of a reef under severe pressure.
The US National Oceanic and Atmospheric Administration (Noaa) says that the temperature increase in the oceans as a result of climate change is the main cause of bleaching.
According to London's Natural History Museum, coral reefs have an estimated global value of £6tn each year.
This is partially a result of their contribution to the fishing and tourism industries.
In addition, the ridges in reefs act as barriers and can reduce wave energy by up to 97%, providing coastal areas with crucial protection against threats such as tsunamis.
They help protect areas such as mangrove forests and seagrass beds that act as nurseries for marine animals, as well as human coastal populations.
Barrier reef under threat
In 2019, an Australian government report downgraded the outlook of The Great Barrier Reef from "poor" to "very poor" as a result of climate change.
It said rising sea temperatures - thanks to greenhouse gas emissions from human activity - remained the biggest threat to the reef.
The reef was designated a World Heritage site in 1981 for its "enormous scientific and intrinsic importance", but in recent years it has been increasingly damaged by warmer seas, which have killed off coral and affected its long-term health.
Noaa researchers say that, if the bleaching is not severe, it is possible for the coral to recover.
However, scientists are concerned that we are pushing the delicate marine ecosystems beyond their ability to cope. This means that natural wonders sometimes described as the "rainforests of the seas" could be reaching their breaking point.