During the first few months of 2020 clear skies and calm weather led to very warm water temperatures throughout most of the Great Barrier Reef region. Water temperatures exceeded 30°C for many weeks. It is now becoming clear that this warm water has caused another mass coral bleaching event even more widespread than the catastrophic bleaching events of 2016 and 2017. Inshore reefs the entire length of the Great Barrier Reef have been affected as have offshore reefs between Cairns and Mackay.
This widespread coral bleaching event has impacted reefs in our area of the Whitsundays. Recent surveys on Rattray and Saddleback Islands reveal the extent of the problem.
Drones-eye view of the fringing reef at Saddleback Island showing the pale bleached corals on the reef slope and outer reef flat
All the acroporid and pocilloporid corals in shallow water were completely bleached but a range of other coral species were also bleached down to over 10 metres depth. Many of the soft corals were also bleached as were most fire corals. Many of the corals were fluorescing bright colours, a common occurrence during bleaching events. Although most of the corals were still alive some colonies were partially dead. Water temperatures a few days ago were 28°C, down several degrees from the summer peak. It is possible that many of the bleached corals will be able to recover their zooxanthellae and survive but this is going to be a slow process.
The brown parts of this bleached Acropora staghorn colony have already died. It is too early yet to tell how extensive coral mortality will be due to this bleaching event.
