Scientists at odds over prognosis of Great Barrier Reef

Aussie scientists are at odds of the impact of the localised coral bleaching found on the Great Barrier Reef as the authorities ramp up monitoring in the highest risk period.

Human induced climate change has been increasing the frequency of mass coral bleaching events as areas of the Pacific such as Fiji, Kiribati and New Caledonia begin suffering a mass bleaching event from El Nino re-enforced warm water travelling through the equatorial pacific.

Patchy coral bleaching has been detected in multiple, mainly shallow areas of the Great Barrier Reef (GBR) where corals are frequently exposed to sunlight. However with sea surface temperatures fluctuating 2.5 degrees Celsius above average across the marine park, March is representing its highest risk period.

"We're down to the wire now -- the 'mild and widespread' bleaching we're seeing now is the result of very warm conditions over the past few weeks," Director of the ARC Center for Excellence for Coral Reef Studies at James Cook University, Professor Terry Hughes said in a statement on Wednesday.

Australian scientists, including Hughes have said these major bleaching events "didn't exist 30 years ago" and are entirely a consequence of the global failure to tackle greenhouse gas emissions, highlighting the importance of limiting average global temperature rises to below two degrees Celsius.

However James Cook University marine geophysicist Professor Peter Ridd believes rather than "another scare story" on the coral bleaching that is ultimately human induced, the reef will fair better and potentially grow from the rise in temperature.

Ridd argues the annual and spatial variability of water temperature is far greater than the small average temperature rise over the last century, thus temperature rises would have broken the bleaching threshold "long before marine biologists first noticed bleaching".

"All the corals that live on the GBR live in water around Indonesia where the temperature is much higher than in the GBR but grow much faster and better than our reefs," Ridd said.

"We should be predicting that the GBR will grow better from a modest temperature rise.

"This is yet another scare story and in the end it will reflect badly on science."

Coral reefs are one of the most important and productive marine ecosystems that the world depends on for tourism and fishery sustainability.

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, and when bleaching is prolonged, the animal can die.

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 hoping for bad weather, such as clouds, rain and storms to mix the water and keep temperatures at bay on the GBR, otherwise the still conditions -- ideal for tourists -- over the next few weeks will ramp up the heat. Endit