Let's dive into the past summer on the glorious Great Barrier Reef!
The Reef experienced relatively mild conditions over much of the 2022-23 summer. This is expected to provide an opportunity for further recovery of coral reefs.
Every year the three leading science and government agencies working on the Reef provide an easy-to-understand summary of how this massive marine ecosystem fared over the summer. Produced by the Great Barrier Reef Marine Park Authority (Reef Authority), the Australian Institute of Marine Science (AIMS) and us, the report focuses on corals, which are the best-known part of the Reef’s ecosystem.
Corals are often described as the ‘engine room’ of the Reef because of their important role in providing a habitat for an enormous variety of plants and animals.
The Reef snapshot: summer 2022–23 wraps up the summer and sets the scene for more detailed reports released later in the year, including the Annual Summary Report on Coral Reef Condition. To understand, manage and protect the Reef we need good information on its health from those who study and use it.
So, grab your snorkel and let's explore the five key take-outs from this year's snapshot.
1. Water temperatures and bleaching
Intermittent, short periods of higher-than-average water temperatures led to minor and moderate levels of coral bleaching in isolated areas across the Reef. Minor or moderately bleached corals have a higher likelihood of recovering, whereas severely bleached corals have higher mortality rates.
Conditions on the Reef after the end of summer have also been warmer than usual for this time of year. The Reef experienced unseasonably warm conditions from early to mid-April. However sea surface temperatures slowly cooled over the second half of the month. The forecast for May is for dry and mild conditions for most of the Reef.
Monitoring by the Reef Authority and partners continues. Long-term effects of the coral bleaching of the previous summer (2021-22) will be published later in the year in the AIMS Long-Term Monitoring Annual Summary Report. Last year’s mass bleaching event was less severe than the 2016 and 2017 mass bleaching events. A timeline of key monitoring reports appears on the back page of the Snapshot document.
2. Floods and cyclones
Active monsoon conditions this summer led to above-average rainfall in northern Queensland and subsequent river flooding. Some rivers in the catchment reached major flood levels. Flood plumes reached offshore reefs in the northern region and the Whitsunday Islands in the central region.
Flood plumes affect water quality, mainly by reducing clarity due to increased sediments and nutrients within the water. This can affect seagrass meadows, coral health and spawning and recruitment.
The Great Barrier Reef Marine Monitoring water quality field team collected samples from the affected areas at the time of flooding to better understand the impact. No cyclones crossed the Reef during the 2022–23 summer.
3. Crown-of-thorns starfish
Crown-of-thorns starfish remain at outbreak or potential outbreak levels in the Swain reefs.
The Crown-of-thorns Starfish Control Program continues to work in all three regions to cull starfish down to non-outbreak levels.
4. Cumulative impacts
Compared to previous summers, cumulative impacts were low this summer. This is expected to have provided an opportunity for further recovery of coral reefs on the Great Barrier Reef. While mild conditions have provided relief for much of the Great Barrier Reef this summer, it has experienced a variety of disturbances over the past decade and global action on climate change remains critical.
5. Climate change
Climate change remains the greatest threat to the Reef. It influences weather patterns and the ocean’s temperature, pH level and currents, as well as intensifying the effects of other threats.
The impacts of climate change are escalating, and the Reef is already experiencing the consequences of this. Unfortunately, the events that cause disturbances on the Reef are becoming more frequent, leaving less time for coral recovery.
Here’s what the experts had to say about the 2022-23 summer
Dr Peter Mayfield, CSIRO Executive Director of Environment, Energy and Resources
“It is good news for the Reef that we are able to report relatively low impacts this summer. But the pressures remain.
“We continue unabated in our goal to deliver the best science to tackle a range of pressures on this global icon. We are building on a long history of working with partners in the Great Barrier Reef Marine Park from inland areas to the outer reef.
“Continuing to address the threats to the Reef in parallel remains the best approach for recovery and the Reef's future.”
Josh Thomas, Great Barrier Reef Marine Park Authority Chief Executive Officer
“While conditions this summer certainly provided some relief for the Reef, this does not mean it is out of the woods. It has experienced a variety of disturbances over the past decade, and global action on climate change remains critical.”
Dr Paul Hardisty, Australian Institute of Marine Science Chief Executive Officer
“Climate change means each summer brings increased risk of intense marine heatwaves and more severe cyclones and flooding. We know gains in coral cover can be lost quickly, and the impacts of climate change make it harder for the Reef to recover.
“The Reef is incredibly large, complex and its number one threat is climate change. The combined effort of our three agencies and our partners ensures the best available science is used to inform management decisions to protect it for future generations.”