Smell of death hits Australia's Great Barrier Reef: WWF

The smell of death has inundated Australia's Great Barrier Reef, scientists and environmentalists say, as the ghostly white bleached coral is inundated by an algal slime.

The world's coral reefs have been devastated by a mass bleaching event from warming sea temperatures linked to human induced climate change that was seemingly exacerbated by the El Nino weather phenomenon in the Pacific.

Australia's Great Barrier Reef itself is suffering its worst bleaching event on record. However, overall mortality is 22 percent, 85 percent of which has occurred in the northern third of the reef.

The World Wildlife Fund (WWF) and researchers from James Cook University in Queensland state on Tuesday released photos showing a "ghastly sight" of the bleaching's "ground zero", with hard corals looking like they had been dead for years covered in a brown algal slime.

"Some people see coral bleached white and think it looks pretty. But this is what follows -- it's literally an attack of the slime," WWF-Australia spokesperson Richard Leck said in a statement.

XL Catlin Seaview Survey executive director Richard Vevers, who took the photos at Lizard Island, 250 km north of Cairns, said "it was one of the most disgusting sights I've ever seen" with soft corals "still dying" and the flesh of the coral's animal host "decomposing and dripping off the reef structure."

"I can't even tell you how bad I smelt after the dive - the smell of millions of rotting animals," Vevers said.

Coral reefs are one of the most important and productive marine ecosystems that the world depends on for tourism and fisheries sustainability. The Great Barrier Reef itself is the world's largest living ecosystem, spanning some 2,000 km along Australia's eastern coastline, bringing in billions of Australian dollars from tourism each year.

Coral bleaching occurs when stress such as heat caused the animal to expel the symbiotic algae, loosing vital nutrients and energy reserves, thus color, leading to the wide scale loss of productive habitats for fish.

The coral host then becomes weak and susceptible to disease. When bleaching is prolonged, the animal can die.

The Great Barrier Reef Marine Park Authority (GBRMPA) believes the ecosystem is still resilient enough to survive the current, and likely future major bleaching events, if enough time is provided to recover.

"The agency's strong protective measures, including no-take green zones which make up 33 percent of the Marine Park, play a critical role in maintaining the resilience of the wider ecosystem," GBRMPA chairman Dr Russell Reichelt said.

"This underlying resilience was on display recently when the Australian Institute of Marine Science found coral cover increased by 19 per cent across the Marine Park between 2012 and 2015, nearly doubling in the southern sector due to good early recovery from cyclones and floods."

Recent research suggests corals with high levels of fat or other energy reserves can withstand annual bleaching events, which is critical to predicting the persistence of corals and their capacity to recover from more frequent events resulting from climate change.

Severe bleaching events, however, may take highly impacted coral reefs up to 10 years to recover.

Scientists are also investigating weather deeper coral reefs can act as a refuge for coral and fish species under threat when extreme temperatures become the norm, potentially providing a "seed bank" to re-populate shallow reefs. Endit