I reported earlier on the impact of the 2020 coral bleaching event on our local Whitsunday reefs. We have since found that reefs have also been badly bleached in the Bowen/Cape Upstart region and in the Mackay region. When we did our April surveys on four islands near Mackay we found that between 40-70% of corals were badly bleached with some mortality already happening. During May we found bad bleaching on our survey sites around Bowen with substantial mortality of some coral groups. Bleaching had reduced coral cover on Camp Island reefs, near Cape Upstart, from 25% down to 17% with mortality still ongoing.
When we checked on our local reefs again in July and August we found that some corals had died, some had recovered but others were still badly bleached more than three months since the bleaching event began. Fully bleached corals are not meant to survive more than three weeks but that has not been the case here. It has been found that corals on inshore reefs can get food by absorbing organic detritus that falls on their surface and it may be that this is enabling corals on these fringing reefs to survive for many months even when badly bleached.
Most bleached Millepora or fire coral colonies have died as have many pocilloporid corals and some acroporid corals. In many cases only part of a colony has died with some parts managing to survive. The full extent of reef damage that has been caused by this widespread bleaching event will not be clear for some months. The good news is that when we drove north to resurvey reefs around Snapper Island near Port Douglas we found no evidence of coral bleaching around that island.
Drone view of the Saddleback Island reef in early April 2020 showing the extensive stands of white bleached corals along the shallow reef edge.
Drone view of the same section (but reversed) of Saddleback Island reef in late July 2020 showing most of the shallow water bleached corals have either recovered or died. Look closely and a few white spots, indicating bleached corals, can still be seen.
