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Great Barrier Reef health update

by Great Barrier Reef Marine Park Authority 1 Feb 03:56 UTC
Coral reef © Mark Ullman

A tropical low near the southern coast of the Gulf of Carpentaria caused significant rainfall and cloud cover across northern Australia over the past week, including across the Great Barrier Reef catchment.

Most of the Great Barrier Reef coast and catchment received rainfall, with the highest totals between Princess Charlotte Bay in the far north and Shoalwater Bay in the south.

However, this rainfall has not resulted in flooding of the catchment's major river systems and it is expected to have negligible impacts on the Marine Park.

The recent rain and cloud cover conditions over much of the Marine Park may have some cooling influence on sea surface temperatures over the coming weeks and this will continue to be monitored.

Temperature

The Bureau's ReefTemp indicates sea surface temperatures in the Marine Park have increased since the previous update.

As of 27 January, some inshore to mid-shelf areas in the Far Northern and Southern management areas were 2 to 2.5 degreesC above the January average.

These are the areas that have also accumulated the most thermal stress in the Marine Park since the start of summer.

Local and regional weather conditions will have a key influence on sea surface temperatures over the next few weeks, and we will continue to monitor the situation closely.

The United States National Oceanic and Atmospheric Administration (NOAA) is indicating that parts of the Torres Strait — and the most northern part of the Far Northern management area — are on Bleaching Alert Level 1.

The area from approximately Shelburne Bay south to Cairns is on Bleaching Warning.

From Cairns to the southern boundary of the Marine Park, most inshore to mid-shelf areas are on Warning, while outer shelf areas are on Watch.

In-water temperature loggers monitored by the Australian Institute of Marine Science are currently indicating a high risk of bleaching at Thursday Island in the Torres Strait, and a medium risk of bleaching at Lizard Island in the northern Marine Park.

All other logger locations south of Lizard Island currently indicate no or low risk of bleaching.

Forecast tools from both the Bureau and NOAA agree that some level of thermal stress is likely to be seen throughout the Marine Park in February.

Bleaching levels explained

The United States National Oceanic and Atmospheric Administration (NOAA) use several categories in their heat stress monitoring for coral reefs.

  • No stress: there is no stress level for corals, no hotspots and no bleaching.
  • Bleaching Watch: there is at least one temperature hotspot in the area and marine managers are keeping an eye on this area.
  • Bleaching Warning: bleaching is possible, there are several hotspots with elevated temperatures.
  • Bleaching Alert Level One: significant bleaching is likely, there multiple hotspots with elevated temperatures.
  • Bleaching Alert Level Two: the highest level, severe bleaching and significant mortality are likely.

Reef health

Reports from our Eye on the Reef network indicated isolated instances of low level coral bleaching and coral disease in the Marine Park.

Active crown-of-thorns starfish outbreaks continue in the central and southern Marine Park.

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