Sea surface temperatures continued to cool, dropping by a further 0.4–0.6°C this week across the Marine Park.

Ex-Tropical Cyclone Maila has weakened and was downgraded to a tropical low on 11 April. The system crossed the Cape York Peninsula on 15 April, bringing moderate to heavy rainfall in some areas.

Encouragingly, the National Oceanic and Atmospheric Administration (NOAA) has now reduced the Coral Reef Watch Bleaching Alert Status to no stress conditions across the entire Great Barrier Reef Marine Park, following further drops in sea surface temperatures - reflecting heat stress easing across the Marine Park.

Since Ex-Tropical Cyclone Narelle, reports from the Eye on the Reef network have identified coral damage on some outer reefs in the Northern region. In response, the Reef Authority and Queensland Parks and Wildlife Service will carry out targeted Reef Health Impact Surveys in the Far Northern region in the coming weeks, weather permitting.

Temperature

Despite the recent cooling, sea surface temperatures remain 0.4–0.5°C above the long-term April average. The Far Northern and Northern regions are still experiencing the effects of accumulated marine heatwave exposure from earlier in summer, which may cause bleaching in some coral species.

Rainfall

Weekly rainfall totals were below average across most of the Marine Park catchments over the past week.

Reef health

Over the past week, 42 Reef Health Impact Surveys were conducted across seven reefs in the Marine Park.

In the Northern region, six reefs were surveyed, with coral bleaching ranging from low (1–10%) to very high (61–90%). These bleaching patterns in the Northern region are likely linked to heat stress and flood plume impacts that accumulated over the summer. Coral damage was also recorded on four of the six Northern reefs surveyed, ranging from low to severe, likely caused by storm impacts from Ex-Tropical Cyclone Narelle. Two reefs in the Northern region also recorded moderate levels of coral disease.

Limited surveys in the Far Northern region mean the full extent of coral bleaching is still emerging, but elevated levels are expected given its prolonged exposure to above-average sea surface temperatures.

In the Southern region, one reef was surveyed and no bleaching was recorded.

Additional Eye on the Reef observations from across the Marine Park reported bleaching on 16 of 32 reefs surveyed across the Marine Park.

Crown-of-thorns starfish control

The Crown-of-thorns Starfish Control Program continues to manage ongoing outbreaks across the Marine Park, with updates shared in the first weekly Reef Health Update of each month.

Reef health update | 9 April 2026

Sea surface temperatures continued to cool this week, dropping by 0.2–0.4°C across most of the Marine Park.

Tropical Cyclone Maila (37U) has now formed in the Solomon Sea and has rapidly intensified into a Category 5 system. Current Bureau of Meteorology forecasts show the system tracking into the Coral Sea, with a likely coastal crossing near Cape York Peninsula this weekend or early next week. Maila is expected to bring localised heavy rainfall, increasing the risk of flood plumes in the Marine Park and possible damage to coral and seagrass habitats from strong waves.

Encouragingly, coral bleaching alert levels have eased. The USA’s National Oceanic and Atmospheric Administration (NOAA), which monitors ocean temperatures globally, has downgraded the Northern, Central, and Southern regions to no stress conditions, following further drops in sea surface temperatures - reflecting heat stress easing across the Marine Park.

Temperature

Despite recent decreases in sea surface temperatures, they remain around 0.6–0.7°C above the long-term April average. The Far Northern and Northern regions are still experiencing the effects of accumulated marine heatwave exposure from earlier in summer, which may cause bleaching in some coral species.

Rainfall

Weekly rainfall across most catchments was average or below average, with totals generally under 100mm except for the Wet Tropics region receiving up to 150mm.

Rainfall in March was higher than usual across most Marine Park catchments, with the Cape York, Fitzroy and Burnett–Mary catchments having some of the highest March rainfalls recorded.

Reef health

Over the past week, 19 Reef Health Impact Surveys were completed across five reefs in the Marine Park.

In the Northern region, four reefs were surveyed with high (31–60%) to very high (61–90%) coral bleaching recorded on three reefs. These bleaching patterns in the Northern region are likely linked to heat stress accumulated over the summer combined with earlier flood plume impacts. All four reefs surveyed in the Northern region also showed severe coral damage, likely caused by storm impacts associated with Ex-Tropical Cyclone Narelle.

Limited surveys in the Far Northern region mean the full extent of coral bleaching is still emerging, but higher levels are expected given its prolonged exposure to above-average sea surface temperatures.

In the Central region, one reef was surveyed and no bleaching was recorded.

Additional Eye on the Reef observations from across the Marine Park reported bleaching on 11 of 19 reefs. No coral disease was recorded during the period.

Crown-of-thorns starfish control

As of 31 March 2026, the Crown-of-Thorns Starfish Control Program and Reef Joint Field Management Program response teams have surveyed and, where needed, culled starfish on 187 reefs this financial year.

Of these reefs:

Crown-of-thorns starfish are at sustainable levels on 80 reefs (43%).

Active culling is underway on 60 reefs (32%) to suppress outbreaks.

Starfish have been detected on 47 reefs (25%), and these reefs will be targeted for culling based on priority and actioned when operationally feasible.

The program uses a science-based prioritisation process to focus effort on reefs with high ecological and economic value, with the aim of maximising coral protection.

Sea surface temperatures continue to ease across the Marine Park this week, dropping by around 0.1–0.2°C.

Heavy rainfall from ex-Tropical Cyclone Narelle caused a major flood in the Far Northern region, with the Pascoe River reaching 19.3 metres - the highest level recorded in more than 50 years and likely a one-in-200-year event. The flood plume may affect nearby ecosystems like seagrass meadows and inshore reefs by lowering salinity and increasing exposure to sediments, nutrients, and pesticides.

The Bureau of Meteorology forecasts a tropical low (37U) may form near the Solomon Islands by Thursday, with a moderate to high chance of developing into a cyclone over the weekend. At this stage, it is expected to stay away from the Queensland coast over the next week.

Temperature

Despite recent decreases in sea surface temperatures, they remain around 0.7°C above the long-term monthly average. The Far Northern and Northern regions are still experiencing the effects of accumulated marine heatwave exposure from earlier in summer, which may cause bleaching in some corals species.

Rainfall

Weekly rainfall totals were mostly average or below average across the Marine Park catchment areas during the past week, with up to 100mm of rain recorded over the reporting period.

Reef health

Over the past week, 43 Reef Health Impact Surveys were conducted across seven reefs in the Marine Park. In the Northern region, five reefs were surveyed with coral bleaching ranging from low (1–10%) to very high (61–90%). In the Central region, two reefs were surveyed and no coral bleaching was observed.

Limited surveys in the Far Northern region mean the full extent of coral bleaching is still emerging, but higher levels are expected given its prolonged exposure to above-average sea surface temperatures.

Additional Eye on the Reef observations from across the Marine Park reported bleaching on 9 out of 24 reefs.

High levels of bleaching in the Northern region may be linked to prolonged heat exposure and impacts from flood plumes. Surveys also recorded moderate to extreme coral damage on three Northern reefs, likely from storm impacts related to Ex-Tropical Cyclone Narelle. One Central reef showed low damage from storms activity, and one reef had moderate coral disease.

Crown-of-thorns starfish control

The Crown-of-thorns Starfish Control Program continues to manage ongoing outbreaks across the Marine Park, with updates shared in the first weekly Reef Health Update of each month.