EXPERT REACTION: Coral bleaching on Great Barrier Reef

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This week the Great Barrier Reef Marine Park Authority released a statement on low level coral bleaching occurring on the reef. They write a number of cases has prompted authorities and researchers to step up monitoring, with the Bureau of Meteorology forecasting a high probability of heat stress that would be sufficient to cause further bleaching. Below Australian experts respond.

Organisation/s: Australian Science Media Centre

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  • Great Barrier Reef Marine Park Authority (GBRMPA)
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    Statement from GBRMPA on low level coral bleaching

Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Professor Ove Hoegh-Guldberg is Director of The University of Queensland’s Global Change Institute and a member of The Great Barrier Reef Taskforce on water quality

I am concerned about the outlook for the Great Barrier Reef. The scientific community has been following the very warm conditions this summer and has been concerned that the outbreak of mass coral bleaching was a very strong possibility, The announcement released by GBRMPA yesterday confirms that those concerns were justified. If we continue to experience still and calm conditions for the next two to four weeks, we could see the level and extent of mass coral bleaching increase. We’re not out of the woods yet.
 
If temperatures stay warm for a long time corals will not only bleach, they will also die. At this point they will become covered by algae and that’s when the lights go out on our beautiful and diverse reefs. Patches of reef may recover but with the increase of bleaching events in recent years, more and more white patches of reef will turn into dead algal-coloured coral with fewer fish - so your favourite patch of coral turns into something resembling an underwater desert.
 
This threat of widespread coral bleaching underscores the sensible nature of the funding decision made by state and federal governments to solve the other problems facing the reef such as water quality issues which are exacerbated by climate change. We need to solve both the climate problem and these other localised threats such as pollution because if we don’t deal with either one, we can’t improve the prognosis for the Great Barrier Reef.

The GBRMPA is world class at minimising other stress factors on the reef.  It would be disheartening to see these worthy efforts come to nothing if we don’t solve the problem of climate change. The looming risk of mass coral bleaching is also highlighting the importance of the strong COP21 agreement in Paris to limit average global temperature to well below two degrees Celsius.
 
We have to do everything possible to rein in our emissions or we will see more and more of these climate related threats, which paint a gloomy future for the reef.

Last updated: 03 Nov 2016 8:17pm
Professor Terry Hughes is an ARC Laureate Fellow and Director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, Queensland. Professor Hughes is also the convenor of the National Coral Bleaching Taskforce

We convened the taskforce several months ago to plan and coordinate research on a possible third major bleaching event. Of course, we hope that the taskforce remains on standby and that severe bleaching doesn't occur. 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. Whether the bleaching dissipates or gets worse will depend on the local weather over the rest of March. Hopefully it will be cool and cloudy. These major bleaching events didn't exist 30 years ago – they are entirely a consequence of our global failure to tackle greenhouse gas emissions.

Last updated: 03 Nov 2016 5:42pm
Dr David Suggett is an Associate Professor, ARC Future Fellow and leader of the Coral Physiology Processes Group within the Climate Change Cluster at the University of Technology Sydney

The coral reef research community has been on edge for the past year or so as the “Godzilla" El Nino has been raging across the Pacific, producing many instances of significant coral bleaching and mortality already; we returned form an expedition to New Caledonia last month where the corals were really starting to show widespread bleaching in some areas. It looks like here in Australia we are starting to see the first reports of significant bleaching on the Great Barrier Reef, and the forecast is not good. Corals undergo some amount of paling (bleaching) every year when waters are warmest – it is their way of tracking seasonal changes in conditions that are best for growth. However, the anomalously warm waters put this process into over-drive and ultimately kill the corals entirely. The whole process is simply made worse if corals simultaneously have to deal with localised stressors such as nutrient and sediment run off form the land, so it is not entirely unsurprising that the Great Barrier Reef is really starting to feel the effects. 

Mass coral bleaching-induced mortality events are still extremely difficult to predict, so these first reports provide a critically important time for the research community to mobilise and better understand how and why corals bleach – future management strategies rest on solving these unknowns. It’s not just the Great Barrier Reef facing this imminent threat – our coral populations as far south as Sydney Harbour have started to show significant bleaching with water temperatures 2-3oC above average.

Last updated: 03 Nov 2016 5:38pm

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