Great Barrier Reef Summer bleach watch

Summer bleach watch © GBRMPA

The ongoing outbreak of coral-eating crown-of-thorns starfish and possible marine heatwaves are the biggest concerns for the Great Barrier Reef this summer, according to Australia's leading marine experts.

The statement follows the annual meeting of scientists, marine managers, partners and stakeholders — convened by the Great Barrier Reef Marine Park Authority — to assess risks to the Reef over summer.

"The summer months are the highest risk period for coral reefs that are highly sensitive to even small temperature changes," Great Barrier Reef Marine Park Authority Chief Scientist Dr David Wachenfeld said.

"Our climate is changing year-by-year and this is causing changes in the Reef ecosystem — it's under pressure which makes the Reef more vulnerable to possible impacts particularly over summer.

"Protecting coral cover is important for the whole ecosystem — which is why we've boosted efforts to control the coral-eating crown-of-thorns starfish with more vessels and crews out on the water to actively cull these predators.

"With a changing climate, we can't rule out the risk of some level of bleaching — we'll keep watch on the Reef over summer and encourage anyone out on the water to report reef condition through our Eye on the Reef app."

Key findings from this week's workshop:

• The Bureau of Meteorology expects marine heatwaves and below average rainfall this summer — these are the conditions that can lead to bleaching.
• The forecast for below average rainfall over summer means the risk of impacts from high rainfall and flooding are low, however localised events are still possible.
• A below average cyclone season is forecast, however the extent and severity of any cyclones that may occur is unpredictable.
• There are ongoing severe outbreaks of coral-eating crown-of-thorns starfish on parts of the Reef — this is being addressed through the Marine Park Authority's crown-of-thorns starfish control program.
• The Marine Park Authority will be on watch for coral disease outbreaks, given the increasingly significant disease outbreaks affecting reefs in other parts of the world.

"Year-round there's already a network of researchers, rangers, tourism operators and citizen scientists out in the field who supply us with information to assist our understanding of Reef health."

Each year the Marine Park Authority convenes a pre-summer workshop with marine managers, scientists, experts and reef industry representatives to look at how the Reef will fare over summer.

This workshop looked at predictions by the Bureau of Meteorology and USA's National Oceanic and Atmospheric Administration, along with other available information.

The likelihood and risk of thermal stress, rainfall and floods, cyclones and storms, outbreaks of crown-of-thorns starfish and disease and the consequences of these impacts were discussed at the workshop.

Year-round, the Reef Joint Field Management Program undertakes reef health checks throughout the Marine Park.

In 2017-18 more than 1900 in-waters surveys were completed across 189 reefs, which helped us to understand conditions in the Marine Park.

Dr Wachenfeld said climate change was the biggest threat to coral reefs worldwide, and urgent global action was needed to reduce greenhouse gas emissions, along with local actions in the Marine Park to build resilience.