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.