Australian authorities are stepping up response efforts after highly variable but widespread coral bleaching was detected across the Great Barrier Reef.

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 had been detected in multiple, mainly shallow areas of the Great Barrier Reef (GBR) where corals are frequently exposed to sunlight, however the Great Barrier Reef Marine Park Authority (GBRMPA) on Monday said diver teams had detected severe bleaching of inshore reefs north of Lizard Island, 250 kilometers north of Cairns, with moderate bleaching on mid-shelf reefs.

"This is the result of sea surface temperatures climbing as high as 33 degrees Celsius during February," GPRMPA chairman Dr Russel Reichelt said in a statement.

Cloud cover and heavy rain in the central and southern region of the GBR have provided some relief from the heat stress, though some mid-shelf and outer reefs had displayed minor to moderate bleaching, "some of which is typical for this time of year".

"At this stage, coral mortality also remains low and has only been detected on a small number of reefs," Reichelt said. Around 5 percent of the GBR died when half of the shallow corals bleached in the 1998 and 2002 major bleaching events.

The GPRMPA is stepping up its monitory surveys, especially in the most highly affected areas, however satellite sea-surface temperature readings have been interrupted by the cloud cover, creating difficulties in assessing the potential damage.

"It will be some months before we know the full effects on the Reef," Reichelt said.

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.

"Bleaching is a vivid reminder of the need for all of us to continue building the resilience of coral reefs to give them the best chance of dealt with increased climate change impacts," Reichelt said.

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.

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