Reef Health update | October 2024

Global sea-surface temperatures remain above average across most of the planet.

Sea-surface temperatures across the Great Barrier Reef Marine Park are around 0.6°C higher than average for this time of year but these temperatures are not at levels that typically cause impacts such as coral bleaching.

Sea-surface temperatures across the Marine Park are expected to remain from 0.4 to 1.2°C above average from October to December. However, local weather conditions will have a key influence on sea surface temperatures during the summer.

The El Niño–Southern Oscillation weather pattern’s neutral condition remains, and the Bureau of Metrology predicts these neutral conditions to continue over the summer.

Reef Health summary for September  

This Reef Health update is based on data collected during September, 2024.

In September, 348 Reef Health Impact Surveys (RHIS) were conducted across 31 reefs in the Marine Park.

Reef Health Impact Surveys are a quantifiable survey method used mostly by the Reef Authority, Queensland Parks and Wildlife Service and researchers as well as trained tourism operators.

Most reefs surveyed showed no signs of coral bleaching, with very few cases of minor bleaching reported in each region. Any coral bleaching observed is not likely related to current sea-surface temperatures as they are under the levels that would usually cause coral bleaching. The surveys also found minor damage (for example, from anchor damage) on some corals but no signs of disease in all regions of the Marine Park.

There was average or below average rainfall reported across all Reef catchments in September.

The highest known crown-of-thorns starfish outbreak densities continue at some reefs in the offshore Southern Region (Swain Reefs) and isolated outbreaks remain on several reefs offshore Townsville and Whitsunday in the Central Region.

The Crown-of-thorns starfish Control Program is in operation, helping us to target those veracious coral predators so we can support the recovery of coral ecosystems and their resilience into the future.

Reef management

The Reef Authority collaborates with science and management institutions to maintain a contemporary understanding of Reef health and the impacts of climate change on the World Heritage Area.

The Australian Institute of Marine Science, the Bureau of Meteorology, CSIRO, and other research institutions continue to deliver monitoring and research that documents the long-term trend of Reef conditions and climate patterns. This includes multiple monitoring programs under the Reef 2050 Integrated Monitoring and Reporting Program.

During the summer months, the Reef is more vulnerable to extreme weather events including cyclones, marine heatwaves and flooding – the effects of which are compounded by climate change.

As we move into the warmer months, there is a lot of work being done with our partners to prepare for summer.

We are also preparing for the upcoming coral spawning, which only occurs a few nights of the year. During this phenomenal event, millions of bundles of coral sperm and eggs are released into the ocean allowing for mass reproduction—a positive sign for Reef renewal and regeneration.

You can do your bit to help protect the Reef by following a few simple steps:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef Health update | September 2024

This Reef Health update is based on data collected during August, 2024.

August was a big month in terms of information coming out about the Great Barrier Reef.  

The Scientific Consensus Statement was released earlier in the month, followed by the Australian Institute of Marine Science’s Annual Report on Long Term Monitoring Program. 

The Reef Authority also released the 2024 Great Barrier Reef Outlook Report. This is the fourth report in a series of comprehensive five-yearly reports on the Reef’s health, pressures, management, and potential future.  

The Outlook Report draws on the most current and rigorous science from leading research institutions, Australian and Queensland government agencies, and industry experts.

It gives us both a diagnosis – what is happening on the Reef now – and a prognosis – what the future looks like for the Great Barrier Reef.

The Report tells us that while there has been recovery in some parts of the ecosystem over the past five years – including coral cover and seagrass meadows - the prognosis for the Great Barrier Reef is one of further degradation largely due to the impacts of climate change.

The 2024 Outlook Report includes data up until December 2023 and does not cover the 2024 summer mass coral bleaching event.

Further surveys and monitoring over the next 12 months will help us to understand how much coral on the Reef has recovered from the 2024 summer bleaching event.

Work to monitor and survey the Reef is ongoing.  

Reef health summary for August  

In August, sea surface temperatures were 0.5°C warmer than average across all regions of the Marine Park in August.

A total of 355 in-water surveys were conducted in the Marine Park during August, including 306 Reef Health Impact Surveys (RHIS), a quantifiable survey method used mostly by the Reef Authority, Queensland Parks and Wildlife Service and researchers as well as trained tourism operators.

These surveys found little evidence of coral bleaching, or recent coral mortality.  All reefs surveyed were found to have an average of less than 5 per cent of coral cover bleached or recently dead.

A high-density Crown-of-Thorns Starfish (CoTS) outbreak continues at some reefs in the offshore Southern Region (Swain Reefs) and isolated outbreaks remain on several reefs offshore Townsville and Whitsunday in the Central Region.

The CoTS Control Program resumed in the Northern Region to address the primary outbreak near Lizard Island and offshore Port Douglas. This area is of particular concern as Primary Outbreaks in this region have previously precipitated waves of secondary outbreaks on downstream reefs and regions further south.

Reef Management

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.

The Reef Authority collaborates with science and management institutions to maintain a contemporary understanding of Reef health and the impacts of climate change on the World Heritage Area.

We’ve never had as much information as we do now on the health of the reef. But it’s important to remember that the Great Barrier Reef is the largest living structure on earth – and any reporting only takes up to a point in time.

We have seen the Reef bounce back before from severe impacts such as the consecutive bleaching events in 2016 and 2017. This was followed by widespread coral recovery between 2017 and 2022.

The full impacts the 2024 mass coral bleaching event has had on the long-term trend on coral cover will not be known until the Australian Institute of Marine Science releases its next annual summary report of coral reef condition in 2025.

Reef Health update | August 2024

This Reef Health update is based on data collected during July, 2024.

July 2024 was the second warmest on record for global sea surface temperatures (SSTs). In the Marine Park, SSTs were 0.8 - 1.2°C above the long-term monthly average for July. The El Niño weather pattern’s neutral conditions are expected to continue into Spring and the Bureau of Meteorology predict there is a 50 per cent chance of La Niña conditions developing before the end of the year.

Last week the Australian Institute of Marine Science (AIMS) released its Annual Summary Report of the Great Barrier Reef Coral Reef Condition 2023−24. In some welcoming news, the 2023−24 Summary Report found that coral cover on the Great Barrier Reef is at regional highs in two of the three regions and has increased in all three regions.

It’s important to note that most of the surveys conducted as part of this Report were completed before the 2024 summer mass coral bleaching event.

Further surveys and monitoring over the next 12 months will help us to understand how much coral on the Reef has recovered from the 2024 summer bleaching event. The full impacts the 2024 mass coral bleaching event has had on the long-term trend on coral cover will not be known until the Australian Institute of Marine Science releases its next annual summary report of coral reef condition in 2025.

The Reef Authority is continuing work with the Australian Institute of Marine Science and James Cook University on the coral bleaching impact framework. The categorisation of this year’s marine heat wave and mass bleaching event will be made available later this year.

Reef health summary for July

In-water surveys conducted in July found some coral mortality on a limited number of Reefs in all three regions of the Marine Park. Coral recovery was also observed across the Marine Park. Survey results show that very little bleached coral remains on the observed reefs, as current sea surface temperatures are below the threshold that typically causes bleaching.

This indicates that we can expect only minimal additional mortality beyond what has already been recorded from the 2024 mass coral bleaching event.

Rainfall

Average rainfall was observed in July in the northern Marine Park catchment areas.

Areas north of Cairns experienced above average rainfall, however no elevated sediment loads in the Marine Park were reported.

Reef health

A total of 278 in-water surveys were conducted in the Marine Park in July, of which 178 were Reef Health Impact Surveys (RHIS), a quantifiable survey method used mostly by the Reef Authority, Queensland Parks and Wildlife Service and researchers as well as trained tourism operators.

Some coral mortality was recorded in reefs off Cape Melville, South of Cairns and in the Capricorn Bunker group where corals were exposed to high levels of heat stress over the summer. Very few bleaching observations were reported.

A high-density crown-of-thorns starfish (CoTS) outbreak continues at some reefs in the offshore southern region (Swain Reefs) and isolated outbreaks remain on a few reefs offshore Cairns in the central region.

Crown-of-thorns starfish control program operations resumed in the northern region to address a primary CoTS outbreak near Lizard Island and offshore Port Douglas. This area is of particular concern as primary outbreaks in this region have previously precipitated waves of secondary outbreaks on downstream reefs and regions further south.

Reef management

We rely heavily on key partners including tourism operators and Traditional Owners to conduct in-water surveys which improve our understanding of the variability of coral responses to heat stress and help to quantity any mortality that has occurred post summer.

The Reef Authority collaborates with science and management institutions to maintain a contemporary understanding of Reef health and the impacts of climate change on the World Heritage Area.

The Australian Institute of Marine Science, the Bureau of Meteorology, CSIRO, and other research institutions continue to deliver monitoring and research that documents the long-term trend of Reef conditions and climate patterns. This includes multiple monitoring programs under the Reef 2050 Integrated Monitoring and Reporting Program.

We’ve never had as much information as we do now on the health of the reef. But it’s important to remember that the Great Barrier Reef is the largest living structure on earth – and any reporting only takes up to a point in time.

We have seen the Reef bounce back before from severe impacts such as the consecutive bleaching events in 2016 and 2017. This was followed by widespread coral recovery between 2017 and 2022.

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.

Reef Health update | July 2024

This Reef Health update is based on data collected during June, 2024.

Winter continues to bring relief for the Great Barrier Reef with cooler ocean temperatures, though they are still above average for this time of year.

As this past summer’s mass coral bleaching event was so widespread and variable, it will take time to determine the full impact on coral communities. Coral recovery and mortality will continue to play out over many months.

Some of the impacts this coral bleaching event has had on the long-term trend in coral cover will be known in the Australian Institute of Marine Science’s Long-term Monitoring Program’s (LTMP) report on coral reef condition when it is released later this year.

The full impacts on the long-term trend on coral cover will not be known until the 2025 LTMP report.

Conditions

Sea surface temperatures across the Reef remain below the threshold that typically causes heat stress to coral. However, sea surface temperatures were still about 0.5 °C above the June average and are currently about 1 °C above the July average.

The El Niño-Southern Oscillation (ENSO) is currently neutral with some models predicting La Niña conditions in the Pacific Ocean later this year. La Niña conditions can result in increased rainfall across much of Australia, cooler daytime temperatures (south of the tropics) and warmer overnight temperatures (in the north).

Rainfall throughout June was low across the Marine Park, which is typical for this time of year across Northern Australia.

Reef Health

The cumulative impacts to the Reef over the past summer have varied greatly, in large part due to the sheer size and biodiversity of the Marine Park. 

During June, 632 in-water surveys were conducted in the Marine Park, of which 543 were Reef Health Impact Surveys, a quantifiable survey method used mostly by the Reef Authority, Queensland Parks and Wildlife Service and researchers as well as trained tourism operators.

Most of these surveys were conducted in the Central and Southern regions of the Marine Park.

The reefs surveyed in June showed less bleached coral cover than those reported in May, and variable levels of coral recovery and mortality were recorded.

In the Central region, ~70% (from 42 reefs) reported no bleaching present and ~80% (from 32 reefs) reported low prevalence (1-10% of coral cover bleached) in the Southern region.

Surveys found low levels of disease and damage in the Southern and Central regions and the few surveys that were conducted in the Northern region found no bleaching or coral mortality.

The highest known crown-of-thorns starfish (CoTS) outbreak density continues at some reefs in the offshore Southern region and isolated outbreaks remain on a few reefs offshore Cairns and Townsville in the Central region.

In the Northern region, south-easterly trade winds have impacted operations, but control efforts will resume when feasible to address the primary CoTS outbreak between cape Melville and Port Douglas. This area is of particular concern as primary outbreaks in this region have previously precipitated waves of secondary outbreaks on downstream reefs and regions further south

Management Actions

We rely heavily on key partners including tourism operators and Traditional Owners to conduct in-water surveys which improve our understanding of the variability of coral responses to heat stress and help to quantity any mortality that has occurred post summer.

The Reef Authority collaborates with science and management institutions to maintain a contemporary understanding of Reef health and the impacts of climate change on the World Heritage Area.

The Australian Institute of Marine Science (AIMS), the Bureau of Meteorology, CSIRO, and other research institutions continue to deliver monitoring and research that documents the long-term trend of Reef conditions and climate patterns. This includes multiple monitoring programs under the Reef 2050 Integrated Monitoring and Reporting Program.

We have seen the Reef bounce back before from severe impacts such as the consecutive bleaching events in 2016 and 2017. This was followed by widespread coral recovery between 2017 and 2022.

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.

The future of the Great Barrier Reef is in everyone’s hands including ours, and yours.

You can do your bit to help protect the Reef by following a few simple steps:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef Health update | June 2024

This Reef Health update is based on data collected during May, 2024.

Winter has brought welcome relief for the Great Barrier Reef and ocean temperatures continue to fall, despite being still above average for this time of year.

The Reef Authority is working with partners to assess the impact of the summer’s mass coral bleaching event that affected all three regions of the Great Barrier Reef. Many reefs remain bleached to varying extents with coral colonies expected to transition to recovery or mortality in the coming months.

We will not know the full impact this bleaching event has had on the long-term trend in coral cover until the Australian Institute of Marine Science’s Long-term Monitoring Program’s  report on coral reef condition is released in 2025.  

Conditions

Sea surface temperatures across the Reef are now below the threshold that typically causes heat stress to corals. However, sea surface temperatures were still about 0.8 °C above the May average and are currently about 0.7 °C above the June average.

The El Niño-Southern Oscillation (ENSO) is currently neutral with some models predicting La Niña conditions in the Pacific Ocean later this year. This can include increased rainfall across much of Australia, cooler daytime temperatures (south of the tropics) and warmer overnight temperatures (in the north).

The greatest rainfall totals for May were received in the Wet Tropics Catchment Region where up to 400 mm was recorded.

The long-range forecast for June to August indicates above average winter rainfall is likely for Queensland’s north tropical coast. However, this is not expected to reach levels that will impact the Marine Park.  

Reef Health

During May 1150 in-water surveys were conducted in the Marine Park, of which 985 were Reef Health Impact Surveys   a quantifiable survey method used mostly by the Reef Authority, Queensland Parks and Wildlife Service and researchers as well as trained tourism operators.

The Southern Region reported the greatest bleaching prevalence with most surveyed reefs exhibiting bleaching of 11−30 per cent of coral cover, and more than 90 per cent on some reefs.

Low to medium levels of bleaching (1−30 per cent of coral cover bleached) were recorded in the Central and Northern regions.

Variable levels of coral mortality have been recorded in all regions of the Reef. The cumulative impacts to the Reef over the past summer have varied greatly, in large part due to the sheer size and biodiversity of the Marine Park. 
There was no to minor levels of coral damage observed in Northern and Southern Reef regions, with mostly minor levels in the Central Region. This is damage associated with various impacts including cyclones or anchor damage.

There was mostly no coral disease observed in the Central and Southern regions with minor to moderate levels of coral disease in the Northern Region.

Crown-of-thorns starfish are at outbreak densities on some reefs in the Swains in the Southern Region while isolated outbreaks of this coral-eating starfish remain on reefs offshore Townsville and Innisfail in the Central Region.

South-easterly trade winds have hindered control operations for this starfish in the Northern Region. Once the weather allows, control efforts will resume in to address the primary outbreak near Lizard Island and offshore Port Douglas.

Management Actions

We rely heavily on key partners including tourism operators and Traditional Owners to conduct surveys which improve our understanding of the variability of heat stress response and help to quantity any coral mortality that has occurred post summer.

The Reef Authority collaborates with science and management institutions to maintain a contemporary understanding of Reef health and the impacts of climate change on the World Heritage Area.

The Australian Institute of Marine Science (AIMS), the Bureau of Meteorology, CSIRO, and other research institutions continue to deliver monitoring and research that documents the long-term trend of Reef conditions and climate patterns. This includes multiple monitoring programs under the Reef 2050 Integrated Monitoring and Reporting Program.

We have seen the Reef bounce back before from severe impacts such as the consecutive bleaching events in 2016 and 2017. This was followed by widespread coral recovery between 2017 and 2022.

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

The future of the Great Barrier Reef is in everyone’s hands including ours, and yours. You can do your bit to help protect the Reef by following a few simple steps: 

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef Health update | 24 May 2024

In March this year, the Reef Authority announced a mass coral bleaching event following aerial surveys which recorded varying levels of bleaching from Gladstone in the south to reefs beyond Lizard Island in the north. This was followed in April with the National Oceanic and Atmospheric Administration in the US declaring a fourth global mass coral bleaching event affecting reefs across more than 53 countries.

The Reef Snapshot: Summer 23-24 was released on 17 April 2024, detailed conditions on the Reef and confirmed the cumulative impacts experienced across the Reef the 2023-24 summer were higher than previous summers.    

Temperature

Sea surface temperatures across the Marine Park are currently below the threshold that typically causes heat stress to corals; however they are still 1 degree above the average for May. 

The El Niño weather pattern has ended as sea surface temperatures in the Central Pacific cooled to neutral El Niño–Southern Oscillation (ENSO) levels in April.

The month of May has seen low rainfall marking the start of northern Australia's dry season.

Reef Health

As detailed in the Reef Snapshot: Summer 23-24, the Great Barrier Reef has been subjected to cumulative impacts over summer.

• Two cyclones crossed the Reef this summer: Cyclone Jasper crossed the Great Barrier Reef north of Port Douglas as a category 2 in December and Cyclone Kirrily crossed the Reef offshore from Townsville as a category 3 in January. Damage to corals by cyclonic waves was reported in the northern and central regions after these events.
• Flood plumes associated with Cyclone Jasper led to freshwater coral bleaching and some mortality, particularly among inshore environments.
• The level of heat stress exposure across the Reef over summer was unprecedented.

Results from aerial and in-water surveys completed to date reveal the bleaching is variable across the Reef, ranging from no bleaching detected in the least exposed areas on some reefs up to over 90 per cent coral cover bleached in the most exposed areas on other reefs. 

We have recorded coral mortality and bleaching across all three regions of the Reef. Corals in the northern and southern sections of the Reef were most affected by heat stress and subsequent bleaching. Coral mortality has been recorded mainly on the shallowest parts of reefs but extending down to 20 metres on those most affected.

Evidence of coral recovery is also being observed, mainly of partially bleached corals. In general, partially bleached corals have a greater likelihood of recovering than fully bleached corals.

Since the beginning of summer, more than 8300 in-water surveys on 273 reefs have been submitted through the Reef Authority’s Eye on the Reef Program by key contributors such as tourism operators, the Crown-of-thorns Starfish Control Program, and Queensland Parks and Wildlife Service. In addition, more than 60,000 images have been collected through the Tourism Reef Protection Initiative, providing a valuable record of coral health. This data will help Reef managers and scientists determine the overall impact of the event, including an assessment of coral recovery vs coral mortality.

Observations to date show that the 2024 coral bleaching event is significant – but the severity of coral bleaching has been variable across the entirety of the Great Barrier Reef.  We will not know the full impact this event has had on the long-term trend in coral cover until the Australian Institute of Maine Science’s Long-Term Monitoring Program Annual Summary Report of Coral Reef Condition in 2025.

What we do know is that the Great Barrier Reef, thanks in part to its sheer size and amazing biodiversity, is a resilient ecosystem.

We have seen the Reef bounce back before from severe impacts such as the consecutive bleaching events in 2016 and 2017. This was followed by widespread coral recovery between 2017 and 2022.

Management Actions

Ongoing ecosystem management actions such as enforcing compliance with the Reef’s zoning plan and controlling the coral-eating crown-of-thorns starfish are critical in supporting and building the Reef’s resilience.

However, this resilience is likely to be constrained by escalating climate change, which is driving more frequent and severe events, including mass coral bleaching.

Safeguarding the long-term future of the world’s coral reefs requires urgent global action to reduce greenhouse gas emissions.

Staff from the Australian and Queensland government are out patrolling the Marine Park as part of the Reef Joint Field Management Program, monitoring and ensuring zoning laws and Marine Park rules are being followed.

Everyone who visits the Great Barrier Reef can do their bit to help protect it. When anchoring boats:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef health update | 26 April 2024

Sea surface temperatures across the whole Great Barrier Reef Marine Park have now cooled to below the average summer maximum. 

Sea surface temperatures are now below the threshold that typically causes heat stress to corals. However, temperatures are still higher than average for April. 

Over the coming months, the Reef Authority will continue working with our partners from Queensland Parks and Wildlife Service under the Reef Joint Field Management Program, the Australian Institute of Marine Science, COTS Control Program, Tourism Operators, and researchers to continue in-water surveys to determine the effects of coral bleaching at varying depths and habitats. This data, alongside the Long-term Monitoring Program information from the Australian Institute of Marine Science, will allow us to quantify any coral mortality that has occurred this summer. 

This is our last weekly Reef Health Update for the 2023–24 summer. From May, we will continue to keep you updated with what’s happening in the Marine Park with monthly updates via this page, and on the Reef Authority’s social media accounts.

Reef health

A total of 730 in-water surveys were conducted in the Marine Park between 10 April–24 April, of which 690 were Reef Health Impact Surveys. 

Coral bleaching was reported on all surveyed reefs. Most reefs surveyed in the Southern Regions had more than 60 per cent of coral cover with coral beaching. Most reefs surveyed in the Central Region exhibited coral bleaching on more than 10 per cent of coral cover while reefs north had more than 30 per cent of coral cover bleached. Variable levels of coral mortality were observed in the Southern and Central regions. 

In the Central region, some minor impacts of damage (e.g. anchor damage, fishing lines etc) and disease were recorded. Mostly no impacts of damage and disease were recorded in the Northern and Southern regions.

The Crown-of-thorns starfish (CoTS) control program has reported emerging primary outbreaks near Lizard Island and offshore Port Douglas. There are also isolated outbreaks offshore Townsville and the Whitsundays, and persistent outbreaks in the offshore Swains Reefs.

Temperature

In some welcome news, the sea surface temperatures across the whole Marine Park have now cooled to below the average summer maximum. 

However, the sea surface temperatures remain above the long-term monthly average for April, with temperatures 1.5°C above average in the Northern Region; 1.25°C above average in the Central; and 1°C above average in the Southern Region. 

While water temperatures are above the monthly average, they are below the threshold that typically causes heat stress to corals.

Rainfall

Heavy rainfall of up to 300mm was received in the Cape York Catchment this past week, but this has not affected the increasing salinity levels north of Cairns. Salinity levels in this area are forecasted to continue increasing to near average levels next week. 

There is a chance that increased cloud and rainfall in the Western Pacific this week could result in increased showers across parts of far northern Queensland.

Reef management

The Reef Authority is working closely with the Australian Institute of Marine Science and the broader observer network to complete further surveys to get a better understanding of the full extent and severity of coral bleaching across the Great Barrier Reef. We will continue to report on what we find, in monthly Reef Health Updates from May. 

Staff from the Australian and Queensland government are out patrolling the Marine Park as part of the Reef Joint Field Management Program, monitoring and ensuring zoning laws and Marine Park rules are being followed. 

Everyone who visits the Great Barrier Reef can do their bit to help protect it. When anchoring boats:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef health update | 19 April 2024

The Reef Snapshot: Summer 2023−24 was released this week, detailing the widespread coral bleaching event on the Great Barrier Reef.

The aerial survey map of bleaching prevalence and key findings of impacts on the Great Barrier Reef over the past summer are included in the Snapshot.

Additional in-water surveys over the next few months are vital to fully understand the variability of heat stress response from different coral species at varying depths and habitats, and to quantify any coral mortality that has occurred.

Preliminary results suggest similar patterns of coral bleaching prevalence when comparing aerial survey data to in-water survey (down to 5 metres depth) data conducted over the same period (22 February–31 March 2024).

International climate models indicate El Niño has ended as sea surface temperatures in the Central Pacific have cooled to neutral El Niño–Southern Oscillation (ENSO) levels. ENSO levels are predicted to remain neutral until at least July 2024.

A tropical low weather system is predicted to form between Queensland and Papua New Guinea in the coming week, with current predictions suggesting the system to be slow moving and may approach Cape York. A second tropical low may also form today in the far northern Coral Sea, expected to track south by Saturday, which could contribute to strengthening wind and wave action in the Marine Park.

Reef health

A total of 661 in-water surveys were conducted in the Marine Park, of which 633 were Reef Health Impact Surveys. These surveys, involving trained participants, provide a robust, quantifiable survey method that is efficient and effective.

Coral bleaching was reported on all surveyed reefs this week, with most surveyed reefs exhibiting bleaching of more than 31 per cent of coral cover.

Some coral mortality has been observed. Other impacts to coral observed this week includes impacts of damage but no impacts from disease.

Crown-of-thorns starfish (CoTS) control program reports emerging primary outbreaks near Lizard Island and offshore Port Douglas (northern Great Barrier Reef), isolated outbreaks offshore Townsville and the Whitsundays (central), and persistent outbreaks in the offshore Swains Reefs (southern).

Temperature

Heat stress continues to accumulate in very limited areas of the Northern Region of the Marine Park; however, temperatures are under the average summer maximums in the Central and Southern regions.

Sea surface temperatures across the Marine Park are mostly ~1.5°C above the long-term monthly average for April in Northern Region; and ~1°C above average in the Central and Southern regions.

Rainfall

Conditions were mostly dry for the Marine Park in the past week, with exception of Wet Tropics catchment area receiving up to 300 mm total weekly rainfall. This has led to the continuation of above average streamflow in these catchments that drain into the Marine Park resulting in the persistence of low salinity levels in waters north of Cairns.
However, salinity level has increased over the past week between Cairns and Cape Melville and are forecast to continue increasing this week. Low salinity levels are expected to persist in waters north of Lockhart River.

Reef management

The Reef Authority is continuing to work with the Australian Institute of Marine Science, Queensland Parks and Wildlife Service, Crown-of-thorns starfish control program, tourism operators, and researchers to coordinate targeted in-water surveys. The data from these surveys, combined with the aerial surveys, will give a greater overview of the severity of coral bleaching. 

Everyone who visits the Great Barrier Reef can do their bit to help protect it. When anchoring boats:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.

Reef health update | 12 April 2024

Heat stress continues to accumulate in the Northern Region, while slowing in the Central and Southern Region. 

The completed aerial surveys covered 1080 reefs from the southern end of the Great Barrier Reef Marine Park to the Torres Strait. The aerial surveys showed prevalent bleaching (>10 per cent coral cover bleached) was present on over 60 per cent of surveyed reefs. Low to no bleaching was evident on 94 per cent of surveyed reefs in the Torres Strait. Very high to extreme bleaching prevalence was most common in reefs both inshore and offshore in the Southern Region, whilst very high bleaching prevalence was most common in inshore and mid-shelf reefs in the Central Region and Northern Region. 

Coordinated in-water surveys are underway to assess how different coral species at different depths and habitats have responded to the accumulated heat stress, and whether any coral mortality has occurred. The Reef Authority in collaboration with science partners, the Australian Institute of Marine Science and CSIRO, will release the Reef Snapshot for Summer 2023-24 next week, which will provide a summary of conditions and impacts over summer and detailed findings from the aerial surveys. 

Tropical Cyclone Paul is situated in the far northern Coral Sea, tracking towards Cape York Peninsula over the weekend and expected to weaken to a tropical low by Saturday. The tropical system is predicted to cross the Marine Park and may result in elevated wind and wave action in the Central and Northern Region of the Marine Park.

Reef health

This week, a total of 68 in-water surveys were conducted across our observer network. Of these, 49 were Reef Health Impact Surveys and all reported coral bleaching of minor to moderate impact. Again, variable levels of coral mortality were found. Other impacts included minor coral damage and disease. 

A persistent crown-of-thorns starfish (CoTS) outbreak continued at offshore Swain Reefs, and isolated outbreaks were found on reefs offshore Townsville and in the Whitsundays. There is also an emerging outbreak near Lizard Island and offshore Port Douglas.

Temperature

Sea surface temperatures are up to 2°C above average across the Marine Park for this time of year. 

Over the past three months the Northern Region has accumulated 12 degree heating weeks, the Southern Region 11 degree heating weeks and the Central Region eight degree heating weeks. 

Sea surface temperatures in the central tropical Pacific are forecasted to return to ENSO-neutral later in autumn 2024.

Rainfall

The Fitzroy catchment received 150mm across the Marine Park, where Central and Northern catchments received up-to 100mm. 

Salinity levels between Cairns and Cape Melville are predicted to increase from 33 to 34 PSU over the week as rainfall eases across the Marine Park.

Reef management

The Reef Authority is continuing to work with the Australian Institute of Marine Science, Queensland Parks and Wildlife Service, crown-of-thorns starfish control program, Tourism Operators, and researchers to coordinate targeted in-water surveys. 

The data from these surveys, combined with the aerial surveys, will give a greater overview of the severity of coral bleaching.

Reef health update | 5 April 2024

Aerial surveys conducted over the Great Barrier Reef have been completed and confirm widespread bleaching across all three regions of the Marine Park.

The surveys conducted by the Reef Authority and the Australian Institute of Marine Science assessed more than 1000 individual reefs, including 836 reefs in the Marine Park and 244 reefs in the Torres Strait region.

Reef health

Of the reefs surveyed by air in the Great Barrier Reef Marine Park:

• A quarter of individual reefs surveyed recorded no to low levels of bleaching. This included reefs in the far north, along the outer shelf north of Port Douglas and north of Lockhart River where less bleaching was observed. 
• Half recorded high or very high levels of coral bleaching. Very high bleaching was found on many of the inshore reefs in the central region of the Marine Park. Several mid-shelf reefs from Innisfail to Cape Melville, including the Lizard Island region, were also affected by very high and extreme levels of bleaching. 
• Less than 10 per cent had extreme levels of coral bleaching. High to extreme levels of bleaching were common in both offshore and inshore reefs in the southern region of the Marine Park.

This week, 63 in-water surveys were conducted across our observer network. Of these, 52 Reef Health Impacts Surveys were carried out and most reported coral bleaching of moderate to severe impact. Variable levels of mortality have been found.  

A persistent crown-of-thorns starfish (CoTS) outbreak continued at some reefs in the offshore Swain Reefs, and isolated outbreaks were found on reefs offshore Townsville and in the Whitsundays. There was also a continued build-up of crown-of-thorns starfish in the northern region with increasing densities near Lizard Island and offshore Port Douglas.

The Reef Authority in collaboration with science partners, the Australian Institute of Marine Science and CSIRO, will soon release the Reef Snapshot for Summer 2023-24, which will provide a summary of conditions over the Great Barrier Reef during the past summer, including impacts from elevated sea surface temperatures, cyclones and flooding.

Temperature

Sea surface temperatures remain 0.5-1.5 degrees above average for this time of year.

A build-up of heat stress is again starting to accumulate in the northern and offshore central region but continues to plateau in the southern region.

Rainfall

Above average March rainfall was recorded for Far North Queensland, resulting in very high streamflow in catchments that drain into the Marine Park. 
This has reduced salinity levels in areas between Cairns and Cape Melville, and north of Princess Charlotte Bay. Flood plumes may result in additional stress on reefs already experiencing prolonged heat exposure.

Reef management

The Reef Authority is continuing to work with the Australian Institute of Marine Science, crown-of-thorns starfish control program, Tourism Operators, and researchers on further in-water surveys.  

The data from these surveys, combined with the aerial surveys, will give a greater overview of the severity of bleaching among different coral types, habitats, and depths. In-water surveys are critical to quantify coral mortality due to bleaching and heat stress over the coming months.  

Over the current holiday period, Marine Park compliance patrols are out in force, particularly at known illegal fishing hotspots, to ensure Marine Park users are doing the right thing to minimise additional stress to the Great Barrier Reef.

Everyone who visits the Great Barrier Reef can do their bit to help protect it.  When anchoring boats:

• Use public moorings where available and do not anchor within no-anchoring areas – they are there to protect the coral.
• Where possible, anchor in sand or mud away from corals and other fragile marine environments. Suitable areas often show up as flat and smooth on your sounder.
• Never wrap anchor rope or chain around bommies or large coral heads.
• If anchoring overnight, anchor before nightfall and double-check the swing room.
• Use your sand anchor and reef pick appropriately to minimise damage.
• Motor towards the anchor when hauling it in and retrieve the anchor when the line is vertical.
• If the anchor is caught on a reef, free it by hand wherever possible.
• Do not force the anchor free by motoring forward.
• Keep watch to make sure the anchor isn’t dragging.    

Reef Health Update | 28 March 2024

Aerial surveys across the far northern region of the Great Barrier Reef, from north of Lizard Island up to and including the Torres Straits, have continued this week. These surveys conclude the campaign of aerial surveys over the Reef.

To date, the Reef Authority and Australian Institute of Marine Science (AIMS) scientists have surveyed 588 individual reefs.

Widespread bleaching of shallow-water corals between Cape Melville (north of Cooktown) and Bundaberg in the south has been recorded.

This coral bleaching event is still unfolding and we are regularly receiving new information that helps us understand the impacts to date.

Reef health

The results of the 588 aerial surveys that have been analysed so far span the areas of the Reef that recorded some of the highest levels of heat stress over the summer months. While there is considerable variability in how much coral bleaching was observed on those reefs, high proportions of the corals that could be seen from the air were clearly bleached. 

Now that we have completed all of the aerial surveys the Reef Authority team and AIMS are now analysing the results. In-water surveys are underway to complement the aerial work. Recent in-water survey data have documented mortality amongst severely bleached corals. 

Crown-of-thorns starfish (CoTS) outbreaks remain at some reefs in the offshore Southern Region (Swain Reefs) and there are isolated outbreaks on some reefs offshore Townsville and the Whitsundays in the Central Region. There is also a CoTS outbreak in the Northern Region, with increasing densities near Lizard Island and offshore Port Douglas.

Temperature

The pattern of coral bleaching on the Reef is consistent with the levels of heat stress that have built up during the Australian summer months. 

Sea surface temperatures continue to decline in the Central and Southern Regions Marine Park; however, are still above the long-term monthly average. 

The southern region of the Marine Park has accumulated unprecedented build-up of heat stress, reaching 14.5-degree heating weeks; the Central Region accumulated just over 12-degree heating weeks and almost 12-degree heating weeks in the Northern Region. 

International climate models suggest the El Niño weather event is decaying, with sea surface temperatures in the central Pacific predicted to return to more neutral levels in May. 

The Great Barrier Reef is one reef system of many around the world that have experienced mass bleaching over the past 12 months. 

Unprecedented summer heat stress in many northern hemisphere coral reefs, such as the Gulf of Mexico, the Caribbean, and Florida Keys, caused widespread, severe coral bleaching and mortality.

Rainfall

Weekly rainfall totals in the Marine Park catchments of up to 300 mm were recorded in the Wet Tropics and up to 400 mm in the Cape York Catchment Region. 

Heavy rainfall has led to very high streamflow in these catchments that drain into the Marine Park with salinity levels as low as 33 PSU persisting between Mission Beach and Cape Melville, and north of Lockhart River.

Flood plumes resulting from freshwater inundation could result in additional stress on coral reefs that have already experienced prolonged heat stress. 

The Marine Monitoring Program (MMP) team have been conducting scheduled monitoring and reactive flood event monitoring, particularly in the Cape York and Wet Tropics catchments to assess water quality in the Reef following the heavy rains, land slips and erosion in the north.

Reef management

The Reef Authority is focused on long-term, local-scale actions to reduce pressure on the Reef year-round – but especially during times of stress.

We’re continuing to target our management actions to make sure any additional stress to the Reef is minimised during this time. 

The crown-of-thorns starfish control program has adapted its approach and is helping gather information about bleaching. This will inform future control efforts to reduce pressures from starfish predation on priority reefs. 

The public is also being called upon to do their part and pay extra attention to the Marine Park zoning rules over the holiday period. The zoning rules help protect the Reef’s precious biodiversity, which is critical at this time of increased stress.

Reef Health Update | 22 March 2024

This week, the Reef Authority has continued working with the crown-of-thorns starfish control program, tourism operators, the Australian Institute of Marine Science and researchers to conduct in-water surveys to better understand of current conditions in the Marine Park. 

Aerial surveys have also resumed this week in the southern Great Barrier Reef, covering the Swains and offshore reefs up to the Whitsundays. These surveys covered 230 reefs, and observed varying levels of coral bleaching on all reefs surveyed. 

Aerial surveys to collect further data from the far-north will continue over coming weeks. The patterns of coral bleaching observed from the aerial surveys are consistent with the heat stress that built up over the summer months in the southern Great Barrier Reef. rial surveys will continue as soon as it’s safe to do so.

Temperature

Recent changes in weather patterns means the build up of heat stress has peaked and is now starting to plateau across the Marine Park.

Heavy rainfall, elevated wind and wave actions associated with weather systems offshore Mackay and northern Australia this past week have had a cooling effect on sea surface temperatures in the Northern and Southern regions, although sea surface temperatures remain above average across the Marine Park.

International climate models suggest the El Niño weather event is decaying, with sea surface temperatures in the central Pacific predicted to return to more neutral levels in May.

Rainfall

In the Far North, the Wet Tropics recorded 400 mm of rainfall, and there has been up to 300 mm in the Cape York Catchment. 

There are low salinity levels between Cardwell and Cape Melville, and north of Lockhart River resulting from above average streamflow in these catchments that drain into the Marine Park.

Reef health

A total of 193 in-water surveys were conducted in the Marine Park between 13 March–20 March 2024. 

Mostly minor to moderate impacts were recorded across surveyed reefs in the past week, noting that the coral bleaching event is still unfolding and its full effects won’t be evident until it ends. Crown-of-thorns starfish outbreaks were found at some reefs in the offshore Southern Region (Swain Reefs), and there were isolated outbreaks on some reefs offshore Townsville and the Whitsundays in the Central Region. 

Outbreaks of these coral-eating starfish continue to build up in the Northern Region with increasing densities near Lizard Island and offshore Port Douglas.

Reef management

The Reef Authority will continue working with our partners to coordinate surveys and get an understanding of what is happening across the Marine Park. 

We’ll continue to target our management programs in the areas that need them most in the coming weeks and as we get more data from in water and aerial surveys.

Reef Health Update | 15 March 2024

This week in-water surveys are continuing, to determine the effects of coral bleaching at a range of depths, so we can better understand the impact of this widespread coral bleaching event across the Marine Park.

Aerial surveys to date have observed variable but widespread coral bleaching across two-thirds of the Marine Park. Aerial surveys across the remainder of the Marine Park, the far northern region from Lizard Island to the Torres Strait, and in the offshore southern Swains region, and the offshore southern region have not been able to occur due to weather conditions. These aerial surveys will continue as soon as it’s safe to do so.

Temperature

Thermal stress continues to accumulate across the Marine Park, however sea surface temperatures have started to decrease as a result of high winds and swell.

Despite some cooler conditions, thermal stress continues, with sea surface temperatures remaining above the long-term average across the Marine Park.  

Sea surface temperatures across the Marine Park range from 0–2.5°C above the long-term monthly average, with the highest anomalies in the northern and southern region.  

A low-pressure system offshore Mackay, and several weak low-pressure systems along northern Australia are expected to bring further cloud cover, heavy rainfall and elevated wind and wave action across the Marine Park, potentially having a cooling effect in these areas.
 

Rainfall

The greatest weekly rainfall totals in the past week were recorded in the Wet Tropics with over 400 mm and up to 400 mm in the Cape York Catchment Region. This has resulted in above average streamflow within these catchments that drain into the Marine Park.  

This is expected to continue to reduce salinity in coastal and inshore areas between Cardwell and Cape Melville, and north of Lockhart River.
 

Reef health

A total of 107 in-water surveys were conducted in the Marine Park between 6 March–13 March.

In the southern region, mostly severe impacts of coral bleaching and minor impacts of damage (e.g. anchor damage, fishing lines etc.) and disease were recorded.

Mostly moderate impacts of bleaching, and minor impacts of damage and disease were found in the central region. Surveys are also being conducted in the northern region that will be reported in the coming weeks.

An outbreak of the coral-eating crown-of-thorns starfish continues at some reefs in the offshore southern region and isolated outbreaks remain on a few reefs offshore in the Central Region. There are also increasing densities of crown-of-thorn starfish near Lizard Island and offshore Port Douglas.  
 

Reef management

The Reef Authority continues to monitor conditions on the Reef and to plan, prepare and respond accordingly to any events that occur.

The Reef Authority is working closely with the Australian Institute of Marine Science and the broader observer network to complete further surveys to get a better understanding of the full extent and severity of coral bleaching across the Great Barrier Reef.

Staff from the Australian and Queensland government are out patrolling the Marine Park as part of the Reef Joint Field Management Program, monitoring and ensuring zoning laws and Marine Park rules are being followed.  

This week, our team of specialists in the crown-of-thorns starfish control program met to review where crown-of-thorns starfish outbreaks are occurring, and how we can target the control program to reduce crown-of-thorns starfish predation on reefs that have been affected by recent coral bleaching and cyclone impacts.

We’ll continue to target our management programs in the areas that need them most in the coming weeks and as we get more data from in water and aerial surveys.

Reef health update – 08 March 2024

Aerial surveys conducted by the Reef Authority in collaboration with scientists from the Australian Institute of Marine Science spanning two-thirds of the Marine Park have now been completed.

These surveys confirm a widespread, often called mass, coral bleaching event is unfolding across the Great Barrier Reef.

Aerial surveys have been completed on over 300 inshore, midshelf and offshore reefs, from Cape Melville north of Cooktown to just north of Bundaberg (southern boundary of the Marine Park). Further surveys will be undertaken pending favourable weather conditions.

Aerial surveys of the Reef have revealed prevalent shallow water coral bleaching on most surveyed reefs and results are consistent with patterns of heat stress that has built up over summer.

Heat stress has not been even across the Reef, and coral bleaching observed is variable.

This unfolding coral bleaching event follows similar reports from reefs around the world during the past 12 months. These Northern Hemisphere reefs have suffered coral bleaching as a result of climate change-driven elevated ocean temperatures, amplified by El Niño conditions in the Pacific Ocean.

While aerial surveys show that this coral bleaching event is widespread, the severity and depth of coral bleaching can only be assessed through in-water surveys. We are continuing to conduct in-water observations with research partners and extended observer network.

This information is critical to informing Reef management, providing a greater understanding of what is happening so we can target management actions to protect the Reef and strengthen its resilience.

Importantly, the Reef has demonstrated its capacity to recover from previous coral bleaching events, severe tropical cyclones, and crown-of-thorns starfish outbreaks.

Bleaching of corals does not always result in coral mortality, with some corals being able to recover if conditions cool.
 

Reef management

Based on the data we’re receiving from a wide range of sources, the Reef Authority in collaboration with the Australian Institute of Marine Science, will be conducting broadscale aerial surveys in the coming weeks to understand the spatial extent of bleaching in all regions of the Marine Park.

The results of these surveys, along with other data from satellite observations and in-water surveys provided by our extended partner network, will help determine the prevalence and spatial extent of coral bleaching in these regions, and overall will provide a more comprehensive understanding of conditions across the Reef.

The Crown-of-thorns Starfish Control Program team has been undertaking control efforts and surveillance at numerous reefs during the past month.

Marine Park rangers from our Reef Joint Field Management Program are continuing to undertake in-water surveys and aerial surveillance throughout the Marine Park as part of routine observations.

On-water programs such as crown-of-thorns starfish control, Land and Sea Rangers, Eye on the Reef, Master Reef Guides, the Tourism Reef Protection Initiative, and our science partners, all play a role in improving our understanding of Reef health and undertaking activities to enhance resilience.

Reef health update – 01 March 2024

 Summer is a high-risk period, and we are continuing to monitor and respond to impacts on the Reef, with our partners.

Sea surface temperatures continue to exceed monthly averages across the Marine Park.

Last week, together with the Australian Institute of Marine Science, we undertook aerial surveys in the southern region of the Marine Park over reefs in the Keppel Group, Capricorn-Bunker Group, and surrounds.

These surveys confirmed reports of extensive bleaching in this area, within both nearshore and mid-shelf areas.

This is in line with spatial patterns of accumulated heat exposure in the southern region which has experienced elevated sea surface temperatures for up to 13 weeks.

In-water surveys will provide better detail on the depth and severity of coral bleaching at the coral colony level within the southern region, as we continue to receive data from our extended observer network.

Some reefs between Mackay and Whitsundays were also surveyed with limited bleaching observed on these reefs. Further surveys will be undertaken in these areas and others in the central region over the weekend.

Available data from in-water surveys in both the central and northern region, and preliminary aerial surveys from the central region, indicate minor to moderate bleaching on surveyed reefs in these regions, primarily in shallow reef habitats.
 

Temperature 

Thermal stress is continuing to accumulate, with sea surface temperatures remaining above the long-term average across the Marine Park.

The highest anomalies are in the northern and southern regions of the Marine Park.

Exposure to elevated sea surface temperatures (degree heating weeks) is approximately eight weeks in the northern region, and approximately 10 weeks in the central region.

Persistent cloud cover for approximately 12 days, has had some cooling effect on sea surface temperatures just north of Townsville in the nearshore central region, however, sea surface temperature anomalies remain above average.
 

Rainfall

Over the past week, northern catchments have received up to 150mm of rainfall.

Rainfall totals across the central catchments has been up to 400mm, and up to 100mm in the southern catchment areas.

The Wet Tropics catchment has recorded over 570mm of rainfall, resulting in above average streamflow in the catchments that drain freshwater into the Marine Park, leading to reduce salinity in nearshore areas where freshwater intrusion has occurred.
 

Reef health

A total of 215 in-water surveys were conducted in the Marine Park between 21 – 28 February, in the southern region the reports documented coral bleaching impacts that were mostly very high, with no impacts of coral damage and minor impacts of coral disease.

Mostly minor to moderate impacts of bleaching were recorded in the central and northern regions with other minor impacts of damage (e.g. anchor damage, fishing lines etc.) and disease.

An outbreak of crown-of-thorns starfish remains persistent at some reefs in the offshore southern region (Swain Reefs) and isolated outbreaks remain on a couple of reefs offshore Townsville and the Whitsundays in the central region.

The northern region continues to be a hot spot for outbreaks of crown-of-thorns starfish, with high densities detected at reefs near Lizard Island and offshore Port Douglas.
 

Reef management

Based on the data we’re receiving from a wide range of sources, the Reef Authority in collaboration with the Australian Institute of Marine Science, will be conducting broadscale aerial surveys in the coming weeks to understand the spatial extent of bleaching in all regions of the Marine Park.

The results of these surveys, along with other data from satellite observations and in-water surveys provided by our extended partner network, will help determine the prevalence and spatial extent of coral bleaching in these regions, and overall will provide a more comprehensive understanding of conditions across the Reef.

The Crown-of-thorns Starfish Control Program team has been undertaking control efforts and surveillance at numerous reefs during the past month.

Marine Park rangers from our Reef Joint Field Management Program are continuing to undertake in-water surveys and aerial surveillance throughout the Marine Park as part of routine observations.

On-water programs such as crown-of-thorns starfish control, Land and Sea Rangers, Eye on the Reef, Master Reef Guides, the Tourism Reef Protection Initiative, and our science partners, all play a role in improving our understanding of Reef health and undertaking activities to enhance resilience.

Reef health update – 23 February 2024

In-water surveys provided through our extended observer network, and aerial observations conducted as part of our routine Reef Joint Field Management Program, indicate minor to moderate bleaching for surveyed reefs across the Marine Park.

The Reef Authority has also received reports of severe bleaching in the southern region, around reefs in the Keppel Group and Capricorn-Bunker Group, primarily to fast growing coral types in shallow reef habitats.
 

Temperature 

Thermal stress is continuing to accumulate, with sea surface temperatures 0–2°C above average across the Marine Park.

The highest anomalies are in the nearshore central region and the lowest anomalies are in the nearshore northern region.

Elevated sea surface temperatures have been observed in the central and southern regions, between Airlie Beach and the southern boundary of the Marine Park, for approximately nine to 11 weeks, and for approximately seven weeks in the northern region.

Data from a limited number of the Australian Institute of Marine Science’s in-water temperature loggers, suggest there has been no cooling effect on the sea surface temperatures from the sustained cloud cover in the northern and central regions over the past week.
 

Rainfall

Over the past week, a tropical low and monsoon trough brought heavy rainfall to northern catchments, with some areas receiving up to 300mm.

Rainfall totals across the central and southern catchment areas ranged from 5––200mm.

Greatest weekly rainfall totals were recorded in the Wet Tropics catchment area resulting in above average streamflow in catchments that drain freshwater into the Marine Park, leading to reduced salinity where freshwater intrusion has occurred.
 

Reef health

Of the 187 surveys conducted in the central and southern region of the Marine Park between 14 and 21 February, most reported minor to moderate coral bleaching, minor coral disease, and minor damage.

Known crown-of-thorns starfish outbreak densities continue to be highest at some reefs in the offshore southern region at the Swains Reefs. Isolated outbreaks remain on a couple of reefs in the central region offshore Townsville and the Whitsundays.

Increasing densities of the coral-eating starfish, near Lizard Island and offshore Port Dougals, indicate the continued build-up of a primary crown-of-thorns starfish outbreak in the northern region.
 

Reef management

The Reef Authority in collaboration with the Australian Institute of Marine Science, will conduct a helicopter survey this weekend to assess the extent of coral bleaching on reefs in the Keppel Group and Capricorn-Bunker Group. This follows several reports of coral bleaching in the southern region of the Great Barrier Reef from our management partners and observer network.

The results of these surveys will help determine the prevalence and spatial extent of coral bleaching in this area.

The Crown-of-thorns Starfish Control Program team has been undertaking control efforts and surveillance at more than 40 reefs during the past month.

Marine Park rangers from our Reef Joint Field Management Program are continuing to undertake in-water surveys and aerial surveillance throughout the Marine Park as part of routine observations.

On-water programs such as crown-of-thorns starfish control, our Reef Joint Field Management Program, Eye on the reef, and the Tourism Reef Protection Initiative all play a part in improving our understanding of reef health and undertaking activities to enhance resilience.

Reef health update – 16 February 2024

Surveys and observations over the past week indicate minor to moderate coral bleaching in all regions of the Marine Park, primarily fast-growing coral types in shallow reef habitats.

Preliminary observations, post tropical cyclone Kirrily, continue to show some branching and plate coral species impacted on a limited number of inshore and mid-shelf reefs off Townsville.

There are no reports of flood plumes affecting the Reef after the rainfall from tropical cyclone Kirrily.

Temperature 

Thermal stress is continuing to accumulate across the Marine Park — sea surface temperatures are exceeding monthly averages and currently 1–2°C above average across the Marine Park.

The highest anomalies are in the nearshore central and southern region, where there’s been prolonged exposure to above average temperatures for several weeks.

Rainfall

Over the past week, a surface trough and humid air masses across northern Australia brought variable rainfall to Reef catchment areas with some receiving up to 200mm.

The monsoon trough is currently active over northern Australia and is predicted to bring increased rainfall and cloud cover to northern Reef catchment areas over the next few days.

Reef health

Of the 255 surveys conducted in the Marine Park between 7 February – 14 February 2024, most reported minor impacts of coral disease and damage.

Known crown-of-thorns starfish densities are highest at some reefs in the outer southern region. Isolated outbreaks remain on a couple of reefs offshore Townsville and in the Whitsundays.

Higher densities of the coral-eating starfish, near Lizard Island and offshore Port Douglas, indicate the continued build-up of a primary crown-of-thorns starfish outbreak in the northern region.

Reef management

As Australia’s key management agency for the Reef, we monitor Reef health year-round and use a range of regulatory tools to manage the Reef like our zoning plan, plans of management, and permits.

On-water programs like crown-of-thorns starfish control, our Reef Joint Field Management Program, Eye on the Reef, and the Tourism Reef Protection Initiative all play a part in building resilience and providing observations.

You can help by reporting what you see through the Eye on the Reef app, following the zoning rules, and reporting sick, injured, dead, or orphaned animals to 1300 ANIMAL (1300 264 625).
 

Reef health update – 9 February 2024

Early observations indicate wave energy from ex-tropical cyclone Kirrily predominately impacted branching and table coral species at inshore and mid-shelf reefs off Townsville. 

Further impacts –– from waves and flood plumes –– to exposed reefs in the Marine Park will be assessed in the coming weeks as model outputs, observations and survey data becomes available. 

Temperature 

Sea surface temperatures are above average across the Marine Park.

In the Central and Southern Regions, it is about 1–1.5°C above average, while parts of the inner Central and Southern Regions are about 1.5–2°C above average. 

Sea surface temperatures in the Northern Region are up to 1°C above average. 

With sea surface temperatures still exceeding monthly averages, thermal stress is continuing to accumulate across the Marine Park.  

Rainfall

Over the past week, a low-pressure trough brought variable rainfall to Reef catchment areas with some areas receiving up to 150mm. 

All impacts from the rainfall entering the Reef will be monitored through surveys conducted as part of the Marine Monitoring Program.

Reef health

Minor to moderate levels of coral bleaching in the Marine Park have been reported, mainly from shallow reef habitats. 

Of the 178 surveys conducted in the Marine Park between 31 January and 7 February 2024, most reported minor impacts of disease, and damage, mainly from shallow reef habitats. 

Within in the Marine Park, the highest known outbreak density of crown-of-thorns starfish continues at some reefs in the outer Southern Region, and isolated outbreaks remain on a couple of reefs in the Central Region. 

Reef management

The Reef Authority continues to monitor conditions on the Reef –– planning, preparing, and responding accordingly to any events over the high-risk summer period. 

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.

Sick, injured, dead, or orphaned animals can be reported to 1300 ANIMAL (1300 264 625).
 

Reef health update – 2 February 2024

Tropical cyclone Kirrily crossed the Great Barrier Reef Marine Park (Marine Park) as a category three system on Thursday 25 January 2024, making landfall as a category two. 

Any potential impacts –– from waves and flood plumes –– to exposed reefs in the Marine Park will be assessed in the coming weeks as model outputs, observations and survey data becomes available. 

Temperature 

Increased cloud cover and rainfall in the northern region have cooled sea surface temperatures to near average. 

In the central and southern regions, sea surface temperatures were ~1°C above average, with parts of the inner central region and southern region reaching ~1.5°C.
As sea surface temperatures exceed monthly averages, thermal stress is accumulating across the Marine Park, which may affect thermally sensitive coral species in shallow reef habitats.

Rainfall

The active monsoon trough, combined with the tropical low system, brought variable rainfall — from 15mm to 400 mm — to catchments connected to the Great Barrier Reef. 

Rainfall from the active monsoon and ex Tropical Cyclone Kirrily may cause reduced salinity of inshore areas, particularly between Cooktown and Bowen.

Any impacts from the rainfall entering the Reef will be monitored through surveys conducted as part of the Marine Monitoring Program.

Reef health

Of the 170 surveys conducted in the Marine Park between 24-31 January 2024, most recorded none to minor impacts of coral bleaching, disease, and damage. 

Within in the Marine Park, the highest known outbreak density of crown-of-thorns starfish continues at some reefs in the outer southern region. 

A severe, isolated outbreak remains on a couple of reefs offshore Townsville and the Whitsundays in the central region. 

Reef management

The Reef Authority continues to monitor conditions on the Reef –– planning, preparing, and responding accordingly to any events over the high-risk summer period. 

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.

Sick, injured, dead, or orphaned animals can be reported to 1300 ANIMAL (1300 264 625).

Reef health update — 25 January 2024

We are closely monitoring Tropical Cyclone Kirrily off the Queensland coast. At this stage, it is predicted to cross near Townsville as a Category 2 system. High winds and wave action are expected throughout the Great Barrier Reef Marine Park. 

Temperatures

Sea surface temperatures are up to one degree above average for all regions of the Marine Park, with the inner Southern Region about one and a half degrees above average. 

Rainfall

Over the last week an active monsoon trough, combined with the tropical low, saw more than 400 mm of rainfall in Cape York and the Wet Tropics catchment. 

Northern Region catchments received between 50-400 mm of rainfall, and between 5-400 mm fell in the Central catchment. However, less than 100 mm fell in the Southern catchment areas.

Any impacts from the rainfall entering the Reef will be monitored through surveys conducted as part of the Marine Monitoring Program.

Reef health

We are keeping a close eye on Tropical Cyclone Kirrily. Like with any cyclone, the impact on the Reef will depend on a range of factors including its intensity, duration, and path.

Of the 227 surveys conducted in the Marine Park between 17 – 24 January 2024, most recorded none to minor coral bleaching, disease, and damage. 

Within the Marine Park, the highest known outbreak density of crown-of-thorns starfish continues at some reefs in the outer Southern Region. Isolated severe outbreaks remain on a couple of reefs in the Central Region. 

Reef management 

Reef Authority monitor conditions on the Reef year-round, stepping up its efforts over the high-risk summer period.

Remember when 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.

Sick, injured, dead, or orphaned animals can be reported to 1300 ANIMAL (1300 264 625).

Reef health update – Friday 19 January 2024

The Reef Authority monitors Reef health year-round, ramping up our monitoring over summer, which is a typically high-risk period from elevated temperatures and cyclones. 

This includes a tropical low in the Coral Sea expected to develop into a tropical cyclone early next week, which may bring increased rain, and add to rainfall and cloud cover in northern and central areas. 

Temperatures

Sea surface temperatures were up to one degree above average for all regions in the Marine Park. High cloud cover may have cooled sea surface temperatures in the Northern and Central regions; however, we don't have reliable satellite data due to the cloud cover. 

Rainfall

Over the last week up to 400 mm of rain fell in northern catchment areas, and between 100-400 mm in the Cape York catchment. Central and southern catchments received between 5-100 mm.

Reef health

There is minor and isolated bleaching on just a few reefs in coastal areas in the path of ex-Tropical Cyclone Jasper, most likely from freshwater flood plumes entering the Marine Park.

Some reefs exposed to high wave energy from ex-Tropical Cyclone Jasper show minor impacts. 

Of the 140 Reef health surveys conducted in the Marine Park between 10 - 17 January 2024, most recorded none to minor coral bleaching, or impacts of coral disease and damage. 

Within the Marine Park, the highest known outbreak density of crown-of-thorns starfish continues within the Swains Reefs in the Southern region, with a severe isolated outbreak persisting in the Central Region. High densities of crown-of-thorns starfish continue to build up in the Northern Region.

Reef management 

We are keeping a close eye on the tropical low in the Coral Sea, drawing on information from the Bureau of Meteorology and other sources.

In the Marine Park, we'll soon receive updates from the three Cairns based Crown-of-thorns Starfish Control program vessels and other surveys.

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.

Sick, injured, dead, or orphaned animals can be reported to 1300 ANIMAL (1300 264 625).

Reef health update – Friday 12 January 2024

The Great Barrier Reef Marine Park Authority (Reef Authority) continues to collaborate with partners to assess any potential impacts on key habitats such as coral reefs, seagrass meadows and islands following the elevated wave energy and flood plumes caused by ex-Tropical Cyclone Jasper.

Temperatures

Sea surface temperatures in the Northern and Central Regions are up to one degree above average, with the Southern Regions about half a degree above average. 

Rainfall

Over the last week up to 120 mm of rain fell in the southern catchment area of the Marine Park, however in the central and northern catchment areas, it was limited to 10 mm total rainfall.

Reef health

Heavy rainfall from ex-Tropical Cyclone Jasper — resulting in freshwater flood plumes entering the Marine Park and decreasing water salinity — led to some minor and isolated freshwater coral bleaching. 

Observations from a limited number of surveys indicate damage from high wave energy associated with ex-Tropical Cyclone Jasper is limited to smaller coral colonies and isolated plate corals resulting from exposure to only moderate wave energy. 

Of 74 Reef health surveys conducted in the Marine Park between 1 – 10 January 2024, 56 recorded none to minor coral bleaching. 

Reef management 

The Reef Authority continues to monitor conditions on the Reef and work with tourism operators to assist their quick return to operations in the Cairns and Port Douglas areas following ex-Tropical Cyclone Jasper. 

Analysing surveys from additional sites over the coming weeks will provide more extensive observations and allow a more detailed assessment of all aspects of Reef health. The three Cairns based Crown-of-thorns Starfish Control program vessels will also be providing updates.

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.

Sick, injured, dead, or orphaned animals can be reported to 1300 ANIMAL (1300 264 625).

Reef health update – Friday 05 January 2024

Tropical Cyclone Jasper entered the Great Barrier Reef Marine Park (Marine Park) as a Category 2 system on 13 December 2023, resulting in intense winds, high rainfall, and flooding in coastal communities between Innisfail and Cooktown. 

The Great Barrier Reef Marine Park Authority (Reef Authority) continues to collaborate with partners to assess any potential impacts on key habitats such as coral reefs, seagrass meadows and islands following the elevated wave energy and flood plumes caused by the cyclone.

Temperatures

During December, sea surface temperatures between Cairns and Townsville were slightly below average, likely due to cloud cover and flooding caused by ex-Tropical Cyclone Jasper. 

The remaining areas of the Marine Park had slightly above average sea surface temperatures, with very limited areas of the Northern Region reaching the highest. 

Rainfall

Up to 100mm of rain fell in the northern and central catchments areas of the Marine Park, with up to 200mm falling in the southern catchment areas. 

Reef health

Extensive flood plumes entering the Marine Park have decreased water salinity in coastal areas between Cooktown and Townsville.

Surveys conducted at a limited number of sites between Cairns to Cape Tribulation indicate that impacts from Tropical Cyclone Jasper were patchy, with some parts of the reef largely untouched while other areas of the same reef show some wave damage, primarily to branching and plate coral species.

Some isolated and minor coral bleaching was also seen at some reefs, likely resulting from freshwater inflow from flooding.

Reef management 

The Reef Authority continues to monitor conditions on the Reef –– planning, preparing, and responding accordingly to any events over the high-risk summer period. It is currently working with tourism operators to assist their quick return to operations in the Cairns and Port Douglas areas following Tropical Cyclone Jasper. 

Working with our extended observer network, we are still building our understanding of the impacts of the cyclone and flooding. Analysis of surveys at additional sites over the coming weeks will provide more extensive observations and allow a more detailed assessment of all aspects of reef health.

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 – 20 December 2023

Our thoughts are with our far north Queensland staff, communities, First Nations people, reef dependent industries, and businesses impacted by major flooding from ex-tropical cyclone Jasper. 

Our immediate focus continues to be on the safety of people, property, and helping businesses recommence operations as soon as possible.

The Reef Authority is working with partners to assess any potential impacts to the Great Barrier Reef Marine Park and islands. 

Temperatures 

We expect to see some cooling effects on sea surface temperatures from the winds, waves, cloud cover and rain generated by ex-tropical cyclone Jasper. 

The ex-tropical cyclone’s extent and persistence meant much of the Reef was covered by clouds, therefore satellite information on sea surface temperatures north of Cairns is currently unavailable — we need clearer conditions to get an accurate picture from the satellites.

Cyclone, rainfall and flooding

The resulting low-pressure system from ex-tropical cyclone Jasper generated significant rainfall and flooding for coastal communities north of Cardwell up into Cape York Peninsula.

For Reef health, the key watch points are the impact of this rainfall and flooding on seagrass meadows and coral reefs in north Queensland and direct wave impacts to coral reefs along the path of the cyclone. 

Impacts will be greater closer to the path of the eye of the cyclone but will be patchy further out. We won’t know the full extent until we receive further information from in the field. 

We’ve received some very preliminary reports from a few of our partners who have been able to access a small number of sites offshore from Cairns and Port Douglas, and these appeared to have fared reasonably well.

The ability to access more offshore sites will slowly increase over the coming weeks, allowing Eye on the Reef surveys to be conducted and more extensive observations of all aspects of reefs that will be required to give a complete picture of the impact. 

Reef management 

We are supporting rescue and recovery efforts coordinated by the Queensland-led disaster management framework, and we are in close contact with permit holders and other Reef partners.

The Reef Authority will be building our understanding of the impacts of ex-tropical cyclone Jasper over the next few weeks.

We will continue to make a full assessment using the results of models and surveys from our extensive network of observers both above and below the water — when it is safe to do so.

Reef health update – 15 December 2023

Tropical cyclone Jasper crossed the Queensland coast as a category 2 system on Wednesday 13 December.

Details of wind and wave strength, including any potential impacts in the Great Barrier Reef Marine Park (Marine Park), will be assessed in the coming weeks as model outputs, observations and survey data becomes available. 

Temperature and rainfall

Since 1 December 2023, sea surface temperatures for most of the Marine Park’s Northern and Central regions were slightly below average due to increased cloud cover from tropical cyclone Jasper.  

Currently, maximum air temperature is around average for most of the Marine Park catchments when compared to the long-term average. 

Heavy rainfall, caused by tropical cyclone Jasper, occurred in the Cairns to Daintree areas.

Low to severe heatwave conditions have eased in most of the Cape York (Far North Queensland) catchment area.  
 

Reef health

In November, the highest known outbreak density of crown-of-thorns starfish remains within the Swains Reefs in the Southern region of the Marine Park.

A severe isolated outbreak persists on Banfield Reef, which is offshore Townsville (North Queensland). 

Reef management

The Reef Authority continues to monitor conditions on the Reef –– planning, preparing, and responding accordingly to any events over the high-risk summer period. 

We will continue to work with our extended network of observers to assess reefs in those areas affected by tropical cyclone Jasper once conditions make this possible. 

The Reef Authority will work with tourism operators to facilitate a quick return of their operations in the Cairns and Port Douglas areas.  

Further, the Reef Authority authorised tourism operators, Traditional Use of Marine Resource Agreement holders, and crown-of-thorns starfish control program teams to reorient or reattach corals overturned or broken by cyclone Jasper.  

This authorisation remains valid for one month as part of assisting the recovery from cyclone Jasper. 

By doing this quickly after corals are broken off and overturned, it gives those corals a chance to reestablish on the Reef and continue providing habitat to other Reef animals. 

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 – 8 December 2023

The Reef Authority continues to monitor conditions on the Reef and prepare for the upcoming summer –– we are keeping a close eye on tropical cyclone Jasper, which is currently in the Pacific. 

As of December 7, tropical cyclone Jasper is tracking as a category 3, and most models predict the system will approach the Queensland coast early next week. 

El Niño conditions and a positive Indian Ocean Dipole are continuing, expected to persist until at least April 2024, increasing the likelihood of a relatively dry and warm summer in the region. 

Forecast models predict sea surface temperatures are likely to peak during January-February 2024 earlier than previous predictions. 
 

Temperatures 

During November, sea surface temperatures throughout most of the Marine Park increased from slightly below to slightly above average. 

Some areas of the Reef’s Southern region (mostly in the Capricorn Cays area) and coastal Central region remained slightly above the monthly average for most of November.

Throughout April–November, global sea surface temperatures were highest on record for their respective months. 

Since late November, there’s been a severe heatwave underway in the Cape York catchment area and it is predicted to continue through to mid-December.
 

Rainfall

Average rainfall across Queensland in November was approximately 51 per cent above the long-term average rainfall, with most catchment areas for the Marine Park receiving up to 200mm for the month. 

Rainfall was lowest in the Cape York catchment area (5mm – 25mm) due to atmospheric conditions. 

The monthly forecast predicts a 75 per cent chance of below-average rainfall compared to the historical average for December.  

Reef health

Of the 1450 Reef health surveys conducted between 1 November – 30 November 2023, 60 surveys recorded mostly minor impacts of coral bleaching in the Marine Park. 

Some minor coral disease and damage were reported in all regions.

Within the Marine Park, the highest known outbreak density of crown-of-thorns starfish continues within the Swains Reefs in the Southern region, with a severe isolated outbreak persisting on the Banfield Reef (North Queensland).

Reef management

The Reef Authority continues to maintain a close watch for any changes in Reef conditions, paying particular attention to the developing cyclone and preparing to respond to any impacts.

In November, our annual pre-summer workshop was held with management partners, Traditional Owners, scientists, tourism, and reef-dependent industry representatives.

Workshop participants focused on current conditions and the latest environmental forecast modelling to understand the likely outlook for summer, and to plan a coordinated approach for the months ahead.

While it is too early to tell exactly what summer will bring and what local and regional conditions will ultimately influence Reef health outcomes, Reef protection continues to be a year-round activity. 

We are working with our partners to protect and strengthen the resilience of the Reef through a range of management actions, including controlling 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.

Protecting the Great Barrier Reef over summer 

While reef protection is a year-round effort, as we come into summer, we're monitoring Reef conditions closely and keeping an eye on the Reef. 

Protecting the Great Barrier Reef requires a partnership involving the Australian and Queensland governments, Traditional Owners, scientists, Tourism operators and industries.

On the water and in the catchment, we're working together to protect the world's natural wonder.

While it's too early to tell exactly what summer will bring, local and regional conditions will ultimately influence Reef health outcomes; the Reef Authority remains focused on reducing cumulative pressures on the Reef.

Discover how the Reef Authority, together with our science and management partners, assess the extent, severity and prevalence of coral bleaching events on the Great Barrier Reef.

From outer space to underwater, you will see the complex monitoring and reporting that happens before, during and after a coral bleaching event on the Reef. 

As part of the summer Reef health response, marine managers and scientists from the Reef Authority, Australian Institute of Marine Science, and James Cook University developed a framework to describe and categorise coral bleaching on the Great Barrier Reef.

This framework describes bleaching events in a clear and consistent way — and enables comparisons to be made between years, over time, and across the Reef.

It considers the four key components that contribute to coral bleaching: exposure, colony response, spatial extent, and prevalence.

• Exposure: satellites, weather stations, gliders and data loggers provide information on the duration of heat stress — how hot, how long, and where.
• Colony response: once coral has been exposed to temperatures, in-water surveys are used to consider how the coral responds — severity, loss of zooxanthellae, mortality, survival.
• Prevalence: in-water and aerial surveys look at what area and what parts of the Reef have been impacted e.g. is it just the reef flat or a bigger area — what percent is impacted, which habitats, at what depths.
• Spatial: broadscale aerial surveys and in-water observations are used to determine whether the scale of impacts — local, regional, widespread, or the total Reef area.

The Reef Authority, Australian Institute of Marine Science, and James Cook University developed the above framework and coral bleaching categories for the Great Barrier Reef.

There are five bleaching event impact categories for the Great Barrier Reef.

At the end of the summer (not week-to-week), the bleaching impact framework will be used to assess how the Reef fared over the summer. Based on the assessment, a category (one to five) will be assigned to describe the bleaching impact. Below is an outline of the categories.