Official statement on coral bleaching

The Great Barrier Reef Marine Park Authority (GBRMPA) is co-ordinating and conducting in-water surveys across the Marine Park as part of its comprehensive response to mass coral bleaching.

Based on the data that it is collecting on a daily basis, the overall picture has been broadly consistent for the past three weeks, whereby bleaching is widespread across the Reef, but not uniform in its severity, GBRMPA says.

The bleaching ranges from severe through to moderate and minor, with reefs between Port Douglas and the tip of Cape York being the most severely affected.

Mass coral bleaching is caused by prolonged exposure to heat stress. This summer's El Nino is a natural episodic event that is occurring on top of the underlying global ocean warming trend caused by climate change. The bleaching was accurately predicted some months in advance by regional climate modelling from the US National Oceanic and Atmospheric Administration.

In-water surveys of bleaching have been ongoing for many weeks, and will continue into May. This work will give the GBRMPA a full picture of the extent of coral die-off, the depth of bleaching, and data on which types of corals have been most affected — none of this information can be detected through aerial surveys alone.

While the data is incomplete, it is clear there will be an impact on coral abundance because of bleaching-induced mortality, mainly in the far north.

"As Marine Park managers we know that, despite the challenges ahead, the most immediate way to help the Reef recover from this serious occurrence of bleaching is to reduce local, regional and catchment-wide stressors so as to support the natural capacity of corals to bounce back," Great Barrier Reef Marine Park Authority Chairman, Dr Russell Reichel, stated.

"The ecosystem’s capacity to recover from disturbances was demonstrated recently in new data from the Australian Institute of Marine Science which identified an average increase in coral cover across the entire Reef of 19.3 per cent between 2012 and 2015.

"A fundamental aspect of supporting the Reef’s resilience is to improve water quality by reducing pollutants and sediments entering the Reef through catchment waterways. Thousands of farmers and graziers are already engaged in this task, and are being backed by significant investment including $140 million through the Australian Government’s Reef Trust.

"As a practical measure to protect existing coral cover, we will also continue our efforts to cull the coral-eating crown-of-thorns starfish — a program which received an additional $7 million under Reef Trust to support culling activities until June 2018.

"Both these tasks are critical and represent opportunities to support the Reef’s resilience in the face of climate change." More at GBRMPA.