This September marked the driest and the third hottest since records began in 1900. 

During September, most of the Marine Park experienced above-average sea surface temperatures for this time of year, with temperatures surpassing monthly averages most often in the outer Southern region. 

There is a 75 percent chance that the Marine Park will receive very little rainfall over the coming month. 

Sea surface temperatures in the central and eastern Pacific continue to exceed El Niño thresholds. Models from the Bureau of Meteorology predict further warming of the eastern Pacific is likely in the coming months with a peak in the period of January to February this summer. 

Reef health and management 

Of the 808 Eye on the Reef program surveys conducted between 1 September – 30 September 2023, 32 surveys recorded minor coral bleaching in the Central region of the Marine Park.

Minor impacts of coral disease and damage were also reported in surveys across different regions of the Marine Park. 

Crown-of-thorns starfish outbreak severity remains highest on reefs in the Swains (Outer Southern Region). 

The Reef Authority monitors conditions on the Reef throughout the year, and particularly during summer.

We use a range of environmental monitoring tools including weather stations and satellite data, and work closely with partners to maintain awareness of Reef condition from in-water and aerial observations, as well as sightings submitted via the Eye on the Reef App and from Marine Park users. 

We also remain focused on targeting direct threats to the Reef by prioritising actions such as enforcing Marine Park zoning rules and culling crown-of-thorns starfish to protect Reef resilience.

We continue to work with partners to address key threats through collaborative efforts. 

If you are out in the Marine Park, you can report what you see through the Eye on the Reef app, and make sure you know your zones to help do your bit in protecting this World Heritage-listed natural wonder. 

Reef health update – August 2023 

This month, the Bureau of Meteorology declared an El Niño event along with a positive Indian Ocean Dipole. When these two climate drivers occur together, they create a drying effect that is typically stronger and more widespread across Australia.

This weather event combination has the potential to reduce rainfall and increase atmospheric and sea surface temperatures. 

This August was the tenth driest and the warmest winter on record, which was dominated by clear weather, often associated with warmer than average sea surface temperatures. Spring is also forecast to be warmer than usual across the country. 

Below-average rainfall is likely for spring, along with warmer-than-usual temperatures. 
Record high sea temperatures globally are likely to impact the weather experienced in Australia for many months.

At this point, the National Oceanic Atmospheric Administration (NOAA) Coral Reef Watch has not issued any bleaching warnings for Australia. 

Reef health

Of the 2919 surveys submitted between 1 August – 1 September 2023, 1118 were Reef Health Impact Surveys (RHIS), and 32 of these reported mostly low impacts of coral bleaching. 

These surveys, along with Rapid surveys and Tourism and Sightings reports, indicated that across the Marine Park, minor coral bleaching, disease, and damage continue to be reported. 

The highest prevalence of low-impact coral bleaching was in the Central region of the Great Barrier Reef. 
Crown-of-thorns starfish outbreak severity remains highest on reefs in the Swains (Outer Southern Region). 

Reef management 

The Reef Authority continues to maintain a close watch for any changes in Reef conditions.

We are working with our partners to protect and strengthen the resilience of the Reef through a range of management actions, including controlling the predatory coral-eating crown-of-thorns starfish and our year-round compliance campaign to deter illegal fishing. 

If you are out in the Marine Park, you can report what you see through the Eye on the Reef app and make sure you know your zones to help do your bit in protecting this World Heritage-listed natural wonder. 

• The United States National Oceanic and Atmospheric Administration (NOAA) use several categories in their heat stress monitoring for coral reefs:
• No stress: there is no stress level for corals, no hotspots and no bleaching.
• Bleaching watch: there is at least one temperature hotspot in the area, and marine managers are keeping an eye on this area.
• Bleaching warning: bleaching is possible; there are several hotspots with elevated temperatures.
• Bleaching alert level One: significant bleaching is likely; there are multiple hotspots with elevated temperatures.
• Bleaching alert level Two: the highest level, severe bleaching and significant mortality are likely.