Reef health update | 18 December 2025

With summer now upon us, reporting has shifted to weekly updates, allowing conditions to be tracked more closely as they change.

While the summer months period typically bring calm conditions and clear water across the Great Barrier Reef, it also often coincides with warming sea surface temperatures across the Marine Park.

The first half of December has continued the warm trend seen throughout spring. Sea surface temperatures remain above average, and while a weak La Niña is underway, rainfall forecasts for the remainder of 2025 suggest conditions are likely to stay close to average.

Temperature

The average monthly sea surface temperatures for November 2025 were the highest on record for the Great Barrier Reef. 
In the first half of December, sea surface temperatures across the Marine Park remained about 1°C above the long-term average, which is slightly lower than the November averages.

Looking ahead, Bureau of Meteorology forecasts show:

• Sea surface temperatures are expected to be 0.4–0.8°C above average throughout January 2026 across most of the Marine Park
• Some offshore areas may reach up to 1.2°C above average
• These forecasts still indicate a warm summer, although predicted temperatures have eased slightly when compared with long-term averages to earlier outlooks.

Degree heating weeks (which measures the duration and intensity of thermal stress) have now begun accumulating on most reefs in the Far Northern region and on some inshore reefs in the Central and Southern regions. While current thermal exposure remains well below thresholds linked to widespread coral impacts, this early onset of degree heating week accumulation has been driven by higher-than-average sea surface temperatures during spring.

Rainfall

A low-pressure trough spanning across the top half of Australia is bringing increased cloud cover and a higher chance of thunderstorms and rainfall across Queensland, especially in the Burdekin and Burnett–Mary catchments and is currently forecasted to persist at least until 21 December.

Reef health

Between 1–14 December 2025, 77 Reef Health Impact Surveys were completed across 11 reefs in the Marine Park.

• In the first week of December, three reefs in the Northern regions recorded low levels (1–10%) of coral bleaching.
• In the second week of December, five reefs in the Northern and Central regions recorded low to high levels of coral bleaching. This isolated coral bleaching is attributed to a flush of fresh water following a high rainfall event in early December in the Northern region of the Marine Park.  

Crown-of-thorns starfish (COTS) continue to affect several reefs, with the most severe outbreaks occurring in the Southern region (Swain Reefs) and the Northern region between Cairns and Lizard Island.

We are working closely with partners to understand conditions across the Reef, drawing on scientific data, modelling, in-water surveys, and observations provided by Marine Park users through the Eye on the Reef app.

Each year, as summer progresses, impacts from warm water are expected. Local conditions and weather patterns will largely determine how reefs respond, highlighting the importance of ongoing monitoring and management.

Our response and ongoing work

Climate change remains the greatest threat to the Great Barrier Reef and addressing it requires urgent global action alongside strong local and regional management to build Reef resilience.

As Reef managers, the Reef Authority works year-round with the Reef Joint Field Management Program, the Crown-of-thorns Starfish (COTS) Control Program, Traditional Owners, researchers, contractors and partner institutions. Together, we ensure management decisions are guided by the most current, reliable and comprehensive Reef health data.

Every day, field officers are monitoring conditions, undertaking conservation actions on reefs and islands, and ensuring people are following the rules designed to protect the Reef.

Our work focuses on strengthening the Reef’s long-term resilience through:

• Managing crown-of-thorns starfish
• Enforcing compliance with the Reef’s zoning plan
• Supporting responsible tourism and recreation
• Collecting, analysing and sharing up-to-date Reef health information.

Our flagship COTS Control Program continues to build on the significant outbreak suppression achieved in recent years. This science-informed, data-driven reef prioritisation approach allows control efforts to be deployed strategically, protecting coral at high-value reefs in a tangible, cost-effective and scalable way.

We are also adapting management approaches to respond to a changing climate and other pressures, including supporting reef rehabilitation efforts and targeted regional actions to maintain ecosystem function.

With calmer winds and clearer conditions typical of the season, summer is one of the most popular times to visit the Reef. Visitors can help protect it by reporting sightings or incidents through the Eye on the Reef app, available on Google Play and the Apple Store.

Reef health update | November 2025

The Great Barrier Reef is entering one of its most active seasons, with turtle nesting, seabird breeding and juvenile fish becoming more visible across the Reef. It is also preparing for its second coral spawning event, following the first spawning in early November. This natural release of eggs and sperm plays an important role in regenerating the Reef and supporting the renewal of its ecosystems.

As this period of renewal unfolds, the Reef is entering summer under continued warm conditions, with sea surface temperatures remaining above average and a weak La Niña underway. While La Niña years can bring increased rainfall, long-range forecasts indicate rainfall is likely to remain around average for the rest of 2025.

Temperature

Throughout November, sea surface temperatures across the Marine Park were 1.3–1.5°C above average.
Looking ahead, Bureau of Meteorology forecasts indicate a high probability of above-average sea surface temperatures continuing through December.

• The Far Northern and Northern regions are expected to remain 1–1.5°C above average.
• The Central and Southern regions are forecast to stay 0.8–1.5°C above average.

Longer-range projections suggest sea surface temperatures will be closer to the long-term averages than those temperatures in recent months. In January, sea surface temperatures across the Marine Park are expected to be 0.6–1.0°C above average.

Reef health

Between 1–30 November 2025, 751 Reef Health Impact Surveys (RHIS) were completed across 59 reefs in the Marine Park with only 1 per cent recording low levels (1–10%) of coral bleaching.

Crown-of-thorns starfish (COTS) continue to impact reefs throughout the Marine Park, with the most severe outbreaks occurring in the Northern region between Cairns and Lizard Island and the Southern region (Swain Reefs).

Since July 2025, the COTS Control Program and Reef Joint Field Management Program have undertaken surveillance and culling across 121 reefs.

• COTS numbers are at sustainable levels on 40 reefs (~33%), supporting coral growth and recovery.
• Culling operations are underway at an additional 61 reefs (~50%) to suppress outbreaks.
• COTS have been detected on 20 reefs (~17%), with culling to begin when resources become available.

Our response and ongoing work

The Reef Authority continues to work closely with the Reef Joint Field Management Program, the COTS Control Program, Traditional Owners, researchers, contractors, and management institutions to ensure contemporary, high-quality data informs decisions across the World Heritage Area.

This collaborative, science-driven approach supports rapid, coordinated management and helps guide where action is needed most.

Our work focuses on building Reef resilience through:

• Managing crown-of-thorns starfish
• Enforcing compliance with the Reef’s zoning plan
• Supporting responsible tourism and recreation
• Collecting and sharing up-to-date Reef health information

COTS control operations continue to build on the regional-scale outbreak suppression achieved in recent years. The data-driven reef prioritisation process used by the COTS Control Program ensures effort is deployed strategically to protect high-value reefs and support the Reef’s long-term resilience.

With calmer winds and clear tropical waters typical of the season, summer is shaping up as one of the best times of year for families, divers and nature lovers to explore the Reef. You can help protect the Reef by reporting sightings or incidents through the Eye on the Reef app, available on Google Play and the Apple Store.

Reef Health update | October 2025

The Great Barrier Reef is gearing up for the annual coral spawning, dubbed “the world’s biggest synchronised sex act”, when billions of corals release eggs and sperm into the ocean in a spectacular mass reproduction event that regenerates the Reef.

Likened to an underwater snow blizzard, researchers predict this year’s coral spawning is expected in early November and early December.

Temperature

Queensland recorded its hottest October on record for average air temperatures, and sea surface temperatures across the Marine Park remained about 1°C warmer than usual.

Forecasts show the water is likely to stay 1 to 1.5°C above average through November.

Looking ahead, temperatures in December are expected to stay 1 to 1.5°C above average in the Far Northern and Northern regions, and about 0.8 to 1°C above average in the Central and Southern regions. Across all areas, the water is likely to stay 0.8 to 1°C above average in January.

Reef health

In October 2025, 359 Reef Health Impact Surveys were carried out across 41 reefs in the Marine Park. Minor coral bleaching was seen only in the Northern region, with no bleaching reported elsewhere.

Crown-of-thorns starfish (COTS) are still affecting many reefs, with the worst outbreaks in the Southern region (Swain Reefs) and the Northern region between Port Douglas and Lizard Island.

Since July, the COTS Control Program and Reef Joint Field Management Program teams have surveyed and removed COTS from 93 reefs.

Of these controlled reefs, COTS numbers are currently at sustainable levels, on 29 reefs (about 31%), allowing coral to grow and recover. Culling is underway at 46 reefs (around 50% of controlled reefs) to control outbreaks and protect coral. COTS have been found on 18 reefs (about 19% of controlled reefs), and culling will begin there when resources become available.

Our response and ongoing work

In late October and early November the Reef Authority conducted crucial Eye on the Reef training with tourism operators, Traditional Owners and teachers. The participants learned how to conduct Rapid Monitoring Surveys, Tourism Weekly Site Monitoring, and Reef Health and Impact Surveys (RHIS) to collect critical data that helps the Reef Authority assess coral health, track recovery, and guide management decisions.

Every data point collected through Eye on the Reef helps us to understand how the Reef is responding to changing conditions, including bleaching and recovery, so we can act where it’s needed most.

The Reef Authority works closely with Traditional Owners, researchers, contractors, and the Queensland Parks and Wildlife Service through the Reef Joint Field Management Program. Together we deliver rapid and coordinated action across the World Heritage Area.

This work focuses on building Reef resilience through:

• Managing crown-of-thorns starfish
• Enforcing compliance with the Reef’s zoning plan
• Supporting responsible tourism and recreation
• Collecting and sharing up-to-date Reef health data to guide decisions

You can help protect the Reef by reporting sightings or incidents through the Eye on the Reef app, available on Google Play and the Apple Store.

Reef Health update | September 2025

Since July 2024, sea surface temperatures around Australia have been the warmest or second warmest on record. Global ocean temperatures have also stayed well above average.

In September, the Marine Park stayed about 1°C warmer than usual, and these higher temperatures are expected to continue into the Austral summer.

Reef surveys showed minimal coral bleaching, but crown-of-thorns starfish outbreaks remain a threat in some areas. 

Temperature 

In September, sea surface temperatures across the Marine Park were about 0.9–1°C above the long-term average. Forecasts show these warmer-than-usual conditions are likely to continue through October to at least December, especially in the Central and Northern regions.

Rainfall 

Rain was recorded along Queensland’s tropical north coast in September, but no flooding or river plumes were reported in the Marine Park.

A negative Indian Ocean Dipole is underway and is likely to persist through spring. This increases the chance of above-average spring rainfall in eastern Australia.

Reef health

During September 2025, 538 Reef Health Impact Surveys were completed across 46 reefs in the Marine Park. Minimal coral bleaching was reported in the outer southern region and no coral bleaching in other areas.

Crown-of-thorns starfish (COTS) continue to affect many reefs. The worst outbreaks are in the Southern region (Swain Reefs) and in the Northern region between Port Douglas and Lizard Island.

The Reef Authority’s COTS Control Program is targeting both the ongoing fourth wave of outbreaks since 2010 and a fifth wave that began in 2022.

Since 1 July this year, the COTS Control Program and the Reef Joint Field Management Program teams have undertaken surveillance and culling on 72 reefs.

Our response and ongoing work

The Reef Authority works closely with Traditional Owners, researchers, contractors, and the Queensland Parks and Wildlife Service through the Reef Joint Field Management Program. Together we deliver rapid and coordinated action across the World Heritage Area.

This work focuses on building Reef resilience through:

• Managing crown-of-thorns starfish
• Enforcing compliance with the Reef’s zoning plan
• Supporting responsible tourism and recreation
• Collecting and sharing up-to-date Reef health data to guide decisions

You can help protect the Reef by reporting sightings or incidents through the Eye on the Reef app, available on Google Play and the Apple Store.

Reef Health update | August 2025

The El Niño–Southern Oscillation remains in a neutral phrase which typically produces more stable weather patterns, although local conditions can vary significantly. The Bureau of Meteorology has updated its forecast for neutral ENSO conditions to persist until at least January 2026.

In 2025, sea temperatures in the Great Barrier Reef have been warmer than usual. This winter was the third hottest ever recorded, and August was the second hottest.

Temperature 

Between 1–31 August, sea surface temperatures across the Great Barrier Reef eased slightly in the north, and in the four management areas:

• Far Northern: dropped from 1.7°C to 1.1°C above average
• Northern: decreased from 1.4°C to 1.1°C above average
• Central: remained stable at around 1.0°C above average
• Southern: recorded the lowest temperatures overall, between 0.6–0.7°C

Warmer-than-average conditions are expected to persist through October 2025.

Rainfall 

There was low rainfall in the Marine Park catchment over August presenting minimal risk of flood plumes or catchment runoff.

Reef health

A total of 288 Reef Health Impact Surveys were completed between 1 – 31 August 2025, across 28 reefs in the Northern, Central and Southern Marine Park regions. Minimal bleaching was reported for all regions.

Crown-of-thorns Starfish (COTS) are affecting many reefs across the Marine Park, with the worst outbreaks in the Southern region (Swain Reefs) and between Port Douglas and Lizard Island.

Since July 2025, response teams from the COTS Control Program and the Reef Joint Field Management Program have worked across 50 reefs to check for starfish and remove them where needed. At those 50 reefs the teams found;

• 15 reefs (30%) have COTS numbers at levels that allow coral to grow and recover.
• 32 reefs (64%) have cull operations active to reduce outbreaks and protect coral.
• 3 reefs (6%) have COTS present, and culling will begin there once resources are available.

Our response and ongoing work

The Reef Authority continues to work closely with the Traditional Owners, researchers, and contractors as well as the Queensland Parks and Wildlife Service through the Reef Joint Field Management Program to deliver rapid, informed and coordinated action across the World Heritage Area.

This work includes building Reef resilience through our compliance and crown-of-thorns starfish control efforts and other active management actions. Collecting and sharing contemporary Reef health data is critical in informing management actions.

We work closely with the tourism industry and local communities to support responsible use of the Marine Park.

Our management actions are geared towards building and supporting Reef resilience, including enforcing compliance with the Reef’s zoning plan and ensuring people are enjoying the Reef in a responsible way. 

You too can help by reporting any incidents through the Eye on the Reef app, which is available for download on Google Play or Apple Store.

Reef Health update | July 2025

El Niño−Southern Oscillation remains neutral

The El Niño−Southern Oscillation remains in a neutral phase which typically produces more stable weather patterns, although local conditions can vary significantly. The Bureau of Meteorology forecasts neutral ENSO conditions to persist until at least December 2025.

Sea surface temperatures across the Great Barrier Reef remain above average, with June 2025 the fourth hottest on record for Marine Park waters.

Between 27 June and 17 July, sea surface temperatures were consistently elevated across all Reef regions:

- Far Northern: +0.8−0.9 °C

- Northern: +0.3−0.8° C, with a moderate warming trend

- Central and Southern: +0.7−1.0° C

Rainfall 

Rainfall in most Reef catchments was below average between 1 June and 20 July. However, rainfall is expected to exceed historical mediums in August which could increase the risk of freshwater flows and sediment runoff into the Marine Park. These conditions can affect coral and seagrass health – especially in inshore areas.

Reef health and monitoring

A total of 338 Reef health impact surveys were completed between 1 June and 20 July across 44 reefs in the Northern, Central and Southern Marine Park regions.

No coral bleaching was observed during this period.

No surveys were conducted in the Far Northern region during this time.

Crown-of-thorns starfish control

A coordinated and proactive response continues to protect coral from the impact of crown-of-thorns starfish (COTS). The Reef Authority’s COTS Control Program, delivered in partnership with the Reef Joint Field Management Program, is a demonstrated effective tool in protecting coral and supporting the health and resilience of the Reef.

Between July 2024 and June 2025:

- 237 reefs were targeted for surveillance and management

- 107 reefs (45% of those targeted) had sustainable COTS numbers, allowing corals to grow and recover

Active culling is underway at 44 reefs with teams working efficiently to reduce starfish densities. The starfish were detected at 86 additional reefs that have been prioritised for action as field resources allow.

This targeted, science-led effort is critical for preserving coral cover and supporting Reef resilience, particularly in areas where coral communities are already under pressure from heat stress. The Swains Reefs in the Southern Regions and reefs between Port Douglas and Lizard Island that still have significant COTS outbreaks, are current priority areas for control efforts. Work to combat coral-eating crown-of-thorns starfish across the Great Barrier Reef is working even under increasing environmental pressures, according to an assessment by University of Queensland researchers. 

Work to combat coral-eating crown-of-thorns starfish across the Great Barrier Reef is working even under increasing environmental pressures, according to an assessment by University of Queensland researchers.

See the research here.

Our response and ongoing work

The Reef Authority continues to work closely with the Traditional Owners, researchers, and contractors as well as the Queensland Parks and Wildlife Service through the Reef Joint Field Management Program to deliver rapid, informed and coordinated action across the World Heritage Area.

This work includes building Reef resilience through our compliance and crown-of-thorns starfish control efforts and other active management actions. Collecting and sharing contemporary Reef health data is critical in informing management actions.

We work closely with the tourism industry and local communities to support responsible use of the Marine Park.

You too can help by reporting any incidents through the Eye on the Reef app, which is available for download on Google Play or Apple Store.