The Great Barrier Reef last year saw its hottest December on record since 1900. 

The Great Barrier Reef Marine Park Authority (GBRMPA) has released its Reef Snapshot for the 2021-22 summer. 

The report outlines how, despite La Niña conditions, the Great Barrier Reef’s waters warmed early in December 2021, exceeding historical summer maximums that typically occur in the hottest summer months.

The snapshot shows that ocean temperatures continued to accumulate heat throughout the summer until early April 2022, which led to the fourth mass bleaching event in seven years.

Experts say that the February 2022 marine heatwave being the first-ever experienced during La Niña conditions and the fourth mass bleaching event since 2016 reflects the growth in frequency and intensity of the threat of heat to the reef system.

The scale of coral mortality is not yet known, but recurrent bleaching events profoundly change the composition of coral communities on the Reef. 

Reports of low coral mortality may reflect shifts in the composition of coral communities, with assemblages being more dominated by resilient and stress-tolerant corals, but an overall loss of biodiversity in the ecosystem. 

To this end, marine biologists say urgent work is still needed to devise a meaningful national plan to reduce the domestic greenhouse gas emissions that are causing water temperatures to rise, and it must be done fast enough for the Reef to survive. 

The snapshot is a new initiative from the Great Barrier Reef Marine Park Authority, the Australian Institute of Marine Science (AIMS) and CSIRO, taking over the important aerial survey work of the National Coral Bleaching Taskforce, led by Professor Terry Hughes. 

The initiative was originally undertaken by a group of scientists, largely working in universities, who felt that the public should be informed about the extent of coral bleaching on the Great Barrier Reef. 

The work has been carried on in the wake of Dr Hughes’ retirement, but the delayed release of the report suggests the bureaucracy and constraints of large institutions are still inhibiting the release of important information to the Australian public.