Updated: 13 June 2016
Our surveys to assess the extent and severity of coral bleaching on the Great Barrier Reef are now complete.
The final leg of surveys was conducted in the remote far north around Cape Grenville.
Our preliminary findings — compiled before the latest Cape Grenville trip — show 22 per cent of coral on the Reef has died due to the worst mass bleaching event on record.
Eighty-five per cent of this mortality occurred in the 600 kilometre stretch between the tip of Cape York and just north of Lizard Island.
Overall, the area below Cairns has escaped significant mortality.
There also continues to be severe bleaching from the tip of Cape York down to some reef areas offshore of Townsville.
In the coming weeks, we will compile and publish a more complete assessment of the bleaching event, before dive teams head back out in October to assess recovery rates of live bleached corals.
- A map is available of average mortality levels at individual reefs to date.
- A map is available summarising the observed bleaching and coral mortality to date.
Coral mortality to date
Far Northern Management Area
From the tip of Cape York to just north of Lizard Island, coral mortality on reefs ranges from very high (50 per cent or more) to low levels (between 0.1 and 9.9 per cent).
Based on initial results of in-water surveys, the average coral loss is 50 per cent in this area.
Cairns–Cooktown Management Area
Between Lizard Island and Tully, coral mortality on reefs ranges from high (between 30 and 49.9 per cent) to low levels (between 0.1 and 9.9 per cent).
Based on initial results of in-water surveys, the average coral loss is 16 per cent in this area. (Note: Surveys around Lizard Island were conducted in March. More recent reports indicate mortality levels are likely to be higher in this management area.)
Townsville–Whitsunday Management Area
Between Tully and the Whitsundays, coral mortality on reefs ranges from medium levels (between 10 and 29.9 per cent) to no mortality.
Based on initial results of in-water surveys, the average coral loss is 3 per cent in this area.
Mackay–Capricorn Management Area
South of Mackay, no bleaching-induced mortality has been detected.
Sea surface temperatures
Bleaching occurs when live corals are stressed, in this case from overheating. If the waters cool down quickly enough, the corals can survive, but if the corals remain stressed for many weeks, they will die off.
According to the Bureau of Meteorology, the Reef recorded its highest average sea surface temperatures for February, March and April since records began in 1900.
Reef waters are still warmer than average for this time of year.
As at 7 June 2016, sea surface temperatures for most of the Marine Park are between one and 2.5 degrees Celsius above the June average (using a baseline from 2002–2011).
This year’s mass coral bleaching on the Great Barrier Reef was triggered by record-breaking sea surface temperatures.Read more on Record-breaking sea surface temperatures
Fishers and spearfishers should consider leaving plant-eating fish to help control seaweed and enable coral larvae to settle and create new colonies.Read more on Responsible reef practices – Spearfishing
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