While it is too early to tell whether mass coral bleaching will occur on the Great Barrier Reef this summer coral-eating crown-of-thorns starfish continue to pose a high risk, according to Australia’s leading marine experts and scientists.
The statement comes after this year’s annual meeting of scientists, Marine Park managers, partners and stakeholders — convened by the Great Barrier Reef Marine Park Authority — to assess risks to the Reef over summer.
Great Barrier Reef Marine Park Authority chief scientist Dr David Wachenfeld said Marine Park managers would keep a close eye on climate models from the Bureau of Meteorology and the US National Oceanic and Atmospheric Administration and welcomed reports from those out on the water over the summer months.
“The climate is changing and we’re concerned about the risk of coral bleaching each summer but it’s too early to tell whether bleaching will occur this summer,” Dr Wachenfeld said.
“There’s a high ongoing risk to corals from the coral-eating crown-of-thorns starfish and control efforts are underway. We will soon add a third crown-of-thorns vessel to the fleet and the Australian Government has committed to continue funding the control program until June 2020.”
The workshop concluded there is a low risk of bleaching from rainfall and flooding — based on a five-point risk scale from very high to low. Coral disease is a high risk, but likely to occur at a localised scale.
“Corals are still dealing with residual stress from two years of mass bleaching and there’s been above average summer and winter sea surface temperatures throughout the year,” Dr Wachenfeld said.
“What happens over the next few months will be driven by sea surface temperatures and the influence of localised weather conditions, such as storms and cyclones.
“All eyes will be on the Reef over summer — our field management officers will continue to check for change on the Reef as part of their surveillance program and we encourage anyone out on the water to report any signs of bleaching through our Eye on the Reef app.”
The El Nino Southern Oscillation is currently neutral, with an increased chance of La Niña developing. La Niña typically sees wetter conditions for eastern Australia and increased cyclone activity. If a La Niña does develop, it is likely to be relatively weak and short-lived, with no strong climate influence on the summer outlook for the Reef.
Generally, the peak time for bleaching is at the end of February when the temperature is hottest.
Australian Institute of Marine Science (AIMS) research scientist Hugh Sweatman said his team would survey 56 reefs along 1000 kilometres of the Great Barrier Reef in coming months, to assess the extent of change caused by bleaching, crown-of-thorns starfish and cyclones.
“The AIMS long-term monitoring program has been observing the Great Barrier Reef for the past 30 years, looking at coral cover and fish communities, and bleaching is one of the things that causes major losses in these communities,” Dr Sweatman said.
“We do see that reefs can recover if they get the chance between disturbances.”
Coral bleaching and a severe tropical cyclone impacted Great Barrier Reef Marine Park over the last two years, though impacts across the 344,000 square kilometres of Marine Park were variable given its vast size — bigger than Italy.
For example, in 2016, even in the northern areas most affected by bleaching, many outer reefs were in better condition.
“Like all coral reefs around the world, the Great Barrier Reef is under pressure,” Dr Wachenfeld said.
“Climate change impacts on coral reefs are predicted to worsen and critically affect the survival of coral reefs globally without the strongest possible mitigation.
“Recent bleaching highlights the importance of global action to reduce greenhouse gas emissions and taking local and regional action to build Reef resilience.”