2016 coral bleaching event

Climate change triggered a global coral bleaching event in 2014, affecting a significant proportion of the world’s coral reefs.

In 2016, the Great Barrier Reef Marine Park was affected by the worst coral bleaching on record.

As a direct result, an estimated 29 per cent of shallow-water coral was lost across the Marine Park — this equates to the loss of more than one in every four shallow water corals (to a depth of approximately 10 metres).

Coral bleaching did extend to deeper corals beyond depths divers typically survey to, but mortality cannot be systematically estimated. Shallow water corals are the most diverse and productive corals and most important to the tourism industry.

However, the impacts from the bleaching were highly variable across the 344,400 square kilometre area of the Great Barrier Reef Marine Park — an area bigger than Italy.

While over 75 per cent of this coral mortality occurred in the far northern region, the southern Great Barrier Reef had little or no mortality from bleaching in 2016.

The impacts of this bleaching event are currently ongoing .

A summary of regional findings is below and a Final Report - 2016 Coral Bleaching Event on the Great Barrier Reef is also available.

2016 coral mortality

Map of the Great Barrier Reef Marine Park that shows the level of coral loss by November 2016
Far northern management area

Cape Grenville region

From the tip of Cape York Peninsula to Lloyd Bay, most reefs surveyed had extreme (75 per cent or more) mortality by late 2016, however outer shelf reefs fared better.

By late 2016, bleaching-induced coral loss was very high on average in this region.

Live coral cover was reduced to very low levels at inshore and mid-shelf survey reefs, but cover remained moderate to high at outer shelf reefs.

Princess Charlotte Bay region

From Lloyd Bay to just north of Lizard Island, coral mortality on surveyed reefs ranged from extreme (75 per cent or more) to moderate levels (between 10 and 29.9 per cent) by late 2016, with outer-shelf reefs faring better.

By late 2016, bleaching-induced coral mortality was very high on average in this region.

Live coral cover was reduced to very low levels inshore, with low to moderate cover at mid and outer shelf survey reefs.

Cairns/Cooktown management area

Lizard Island region

In the Lizard Island region, most reefs surveyed had extreme (75 per cent or more) or very high (between 50 and 74.9 per cent) mortality by late 2016. This also followed other recent declines in coral cover in the region.

By late 2016, bleaching-induced coral mortality was very high on average in this region.

Live coral cover was reduced to very low levels at all survey reefs across the shelf.

Cairns–Port-Douglas region

From just south of Cooktown to Tully, coral mortality on surveyed reefs ranged from high (between 30 and 49.9 per cent) to low levels (between 0.1 and 9.9 per cent) by late 2016.

By late 2016, there was a medium level of bleaching-induced coral mortality on average in this region.

Live coral cover was generally moderate to high in late 2016 in this region.

Townsville/Whitsundays management area

Townsville region

Between Tully and just north of Bowen, coral mortality on surveyed reefs generally ranged from medium levels (between 10 and 29.9 per cent) to low levels, with outer shelf survey reefs having higher mortality (up to very high) and mid-shelf survey having low mortality.

By late 2016, there was a medium level of bleaching-induced coral loss on average in this region.

Live coral cover was generally moderate to high in late 2016 in this region.

Whitsundays region

Between Bowen and Shoalwater Bay, most reefs escaped without bleaching-induced mortality, but two of the surveyed reefs had medium (between 10 and 29.9 per cent) to low mortality.

By late 2016, a low level of coral loss was recorded in this region.

Live coral cover was moderate to high in late 2016 in this region.

Mackay/Capricorn management area

Rockhampton region

South of Shoalwater Bay, no bleaching-induced mortality was detected in 2016.

Live coral cover remained high at mid and outer shelf reefs, but moderate inshore.

Record-breaking temperatures

Mass coral bleaching on the Great Barrier Reef in 2016 was triggered by record-breaking sea surface temperatures.

The rising temperatures reflect the underlying trend of global ocean warming caused by climate change.

A strong El NiƱo also resulted in little monsoon activity and, as a consequence, long periods without cloud cover which would typically have offered corals some respite from heat stress.

According to the Australian Bureau of Meteorology, the Great Barrier Reef recorded its hottest-ever average sea surface temperatures for February, March and April since records began in 1900.

Map showing ocean temperatures around much of Australia were either above average or the highest on record.

Above: Highest on record refers to highest sea surface temperature value since 1900. Decile 10 is the highest 10 percent of records — this category is 'very much above average'. Analysis supplied by the Bureau of Meteorology. Based on the ERSST v4 dataset produced by the National Oceanic and Atmospheric Administration. © Australian Bureau of Meteorology

February 2016

In February 2016, the average sea surface temperature over the Great Barrier Reef was 1.1 degrees higher than the 1961–1990 average.

Further information on graphs is available from the Bureau of Meteorology.

Bar graph of sea surface temperature anomalies for February between 1900 and 2016

© Australian Bureau of Meteorology.

March 2016


In March 2016, the average sea surface temperature over the Great Barrier Reef was 1.3 degrees higher than the 1961–1990 average.

Sea surface temperature anomalies for March between 1900 and 2016

© Australian Bureau of Meteorology.

April 2016

In April 2016, the average sea surface temperature over the Great Barrier Reef was one degree higher than the 1961–1990 average.

Bar graph showing sea surface temperature anamolies for April between 1900 and 2016

© Australian Bureau of Meteorology.

Heat stress patterns

The heat stress was not uniform across the Reef over the hottest period of the year, between December 2015 and March 2016.

The below map shows how heat accumulated over the Reef by the end of March, increasing the risk of coral bleaching.

Local weather patterns, including rain and heavy cloud from ex-cyclone Winston, meant the intensity of coral bleaching in each region varied.

Map of Great Barrier Reef coastline showing heat stress was not uniform across the Reef over summer

Above: The scale used is an indicator of coral bleaching risk. One degree heating day (DHD) is one degree above the long-term average temperature for one day.