Summer weather impacts Australia’s Great Barrier Reef

The summer season weather has provided plenty of impacts on Australia's Great Barrier Reef.  Maximum water temperatures well over 30 deg C (86 deg F) have caused some coral bleaching on many reefs along the Great Barrier Reef .  Sections of many bleached coral colonies have died.  This is the fourth time in the last six years that bleaching has led to coral death and some reefs have been badly affected by these episodes.  There is increasing concern that global warming is responsible for the apparently increasing frequency and severity of these bleaching events and that the situation will get worse in the future.  This is a worldwide problem and not restricted to Australia.

Bleached Staghorn Coral

Several Tropical Cyclones have passed through the Great Barrier Reef over the past summer, breaking up many fragile corals.  Those reefs exposed to these cyclonic conditions have seen lots of coral death caused by high waves whipped up by winds well over 60 knots.  Hits from moderate cyclones like these can reduce coral cover on a reef by up to 50%.  Severe cyclones can kill most living coral leaving only a few damaged colonies.

The wet season in tropical Australia has weighed in with its own impact.  After two years of failed wet seasons this year has seen a big wet.  March rainfalls of almost 80 inches generated massive freshwater run-off into reef areas.  This has further stressed the reef ecosystem and led to some coral death on inshore reefs.

The good news is that studies suggest that the coral reef ecosystem is well able to cope with regular impacts of this sort and bounce back to as good or better than its previous condition.  In good conditions the loss of half the living corals on a reef may be made up again by rapid growth of remaining colonies in only two or three years.  The bad news is that we do not yet fully understand what will happen if climate change continues to increase the frequency of such severe weather episodes.