Like a ghost forest

Great Barrier Reef: 5th mass bleaching in 8 years

A diver at the bleached Great Barrier Reef

(Bild: AFP)

Concern for the Great Barrier Reef off the coast of the Australian state of Queensland: due to significantly increased water temperatures, the fifth mass bleaching of corals in just eight years has been confirmed at this natural wonder. This was announced by the Great Barrier Reef Marine Park Authority (GBRMPA) on Friday.

Experts had already reported a few days ago that due to the recent marine heatwave, a 1100-kilometre-long area stretching from Lizard Island to the Keppel Islands resembled an underwater ghost forest. Aerial photographs have now shown that the new coral bleaching is already very widespread. However, further investigations directly in the water are necessary to accurately assess the severity of the mass bleaching, the GBRMPA wrote.

One of the most species-rich habitats on Earth
The enormous reef is so large that it can even be seen from space. The living organism stretches over a length of 2300 kilometers off the northeast coast of Australia and is considered one of the most species-rich habitats on earth. It is home to hundreds of coral species, 1500 fish species and 4000 different mollusc species.

A diver at the faded Great Barrier Reef

(Bild: AFP)

(Bild: AFP)

(Bild: AFP)

"The Great Barrier Reef is suffering massively from heat stress," warned Laura Puk, a coral and mangrove expert 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." This eighth bleaching event since 2016 is devastating for the World Heritage Site.

Corals "starve" after rejection of algae
When coral polyps are stressed by prolonged heatwaves, they reject the colorful algae that provide them with food and with which they otherwise live together in a mutually beneficial community. They are left pale and white or produce brightly colored algae in a last-ditch attempt to protect themselves. "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 an early change in the weather and a rapid cooling of the water can save the Great Barrier Reef. However, the GBRMPA emphasized that all is not yet lost-and that the bleaching of the cnidarians need not necessarily lead to their death. The reef has already proven its ability to recover from previous coral bleaching events or severe tropical cyclones. But one thing is certain, WWF Australia said: "Five mass bleaching events in eight years show that climate change is putting enormous pressure on the reef."