Relief for recovering Reef as monsoon cools waters

Reporting by Australian Institute of Marine Science

A late summer monsoon in 2026 brought the Great Barrier Reef a reprieve from unfolding coral bleaching, aiding its initial recovery from recent climate-induced disturbances, according to the Australian Institute of Marine Science’s (AIMS) annual survey report on the ecosystem.

Coral cover across all three regions of the Reef increased slightly or remained at similar levels to that recorded last year, indicating limited impacts from 2025’s mass bleaching event, and the regional bleaching event in the Northern and Central regions recorded earlier in 2026.

The Reef faced other impacts from flooding and two tropical cyclones including Narelle, but most of the surveys for this report were completed before its passage as a category 5 system over the Northern region in March. Increases of crown-of-thorns starfish in the Northern Great Barrier Reef over the last few years indicate initiation of the fifth recorded wave of outbreaks for the Reef since the 1960s.

The coral cover levels recorded over the 2025/26 field season were:

Coral cover levels in all three regions of the Reef continue to be above or just below the long-term average.

AIMS Long-Term Monitoring Program (LTMP) leader Dr Mike Emslie said coral cover levels increased modestly or remained stable on many reefs and substantial declines were uncommon.

“The Reef experienced a summer of above average sea temperatures once again, but the late summer monsoon activity, which increased cloud cover and reduced sea temperatures, likely limited the severity and extent of bleaching in the 2025/26 summer,” he said.

“We did not see a repeat of the 2024 and 2025 mass bleaching events, or a repeat of the significant impacts from the 2024 event. Bleaching events vary markedly and do not always result in coral mortality. It depends on the intensity and duration of the heat stress.”

2026 is the 40th year of data for the LTMP, which provides a critical trusted, long-term view of the Reef.

A total of 121 coral reefs were surveyed for this year’s report. Most of the reefs surveyed (106) had moderate to high coral cover (between 10% and 50%):

Of the reefs surveyed, 16% showed a decline in coral cover, 56% showed no change and 28% had an increase.

“While many reefs did not lose coral cover, bleaching likely prevented the continued increases in coral cover that would normally be expected in the absence of disturbance,” Dr Emslie added.

The report includes a detailed examination of impacts from the 2024 mass bleaching event on different types of corals, finding shifts in coral communities not revealed by declines in total hard coral cover. In last year’s report, AIMS detailed substantial declines in coral cover from the high levels of recent years mostly due to the 2024 bleaching event.

“From our detailed surveys of permanently marked sites at 71 reefs, we found that reefs dominated by fast-growing, habitat-building, bleaching-sensitive Acropora corals were the most severely impacted by the event. The reefs with high levels of Acropora now exist in a highly vulnerable state. It’s possible that what looks like complete recovery on these reefs can be reversed in just a year,” said Dr Emslie.