Australia's Great Barrier Reef is experiencing its fifth mass bleaching in just eight years, according to the authority which monitors the health of the world's largest coral reef.
The Great Barrier Reef Marine Park Authority (GBRMPA) announced on Friday that rising ocean temperatures were causing a marine heatwave that was causing massive damage to a 1,100-kilometre-long stretch of reef.
Aerial photographs show that the affected area stretches from the Keppel Islands, about 500 kilometres north of Brisbane, to Lizard Island, north of Cairns.
However, further investigations are necessary to accurately assess the severity of the mass bleaching, the GBRMPA wrote.
The reef, a living organism, stretches some 2,300 kilometres off the north-east coast of Australia and is considered one of the most species-rich habitats on earth. It is home to hundreds of coral species, 1,500 fish species and 4,000 different mollusc species.
"The Great Barrier Reef is suffering massively from heat stress," warned Laura Puk, an expert on corals and mangroves from WWF Germany.
"Severe coral bleaching leads to the death of corals, and if this occurs at short intervals, a reef has no chance of recovering."
Puk explained that when coral polyps are stressed by prolonged heatwaves, they reject the colourful algae that provide them with food and with which they otherwise live together in a symbiotic community.
"Without their symbiotic partners, the corals starve and die," explained Puk. The result is white calcareous skeletons that are soon overgrown by green-brown algae.
Marine conservationists say that only a rapid change in the weather and a rapid cooling of the water can save the Great Barrier Reef.
