Great Barrier Reef suffers third severe bleaching event in five years

Climate change poses a real threat to the future of the world’s reef systems, but some are already feeling that in very real ways. Australia’s Great Barrier Reef is a prime example, having already suffered back-to-back severe mass bleaching events in the past five years. Scientists have this week confirmed it is in the midst of a third, citing the detection of “very widespread bleaching” following a buildup of heat in the preceding months.

Coral bleaching occurs as a result of abnormal temperatures that cause the organisms to expel algae they normally rely on for nutrients and their colorful appearance. In the case of the Great Barrier Reef, warmer waters in the area cause destructive and widespread coral bleaching.

The Great Barrier Reef has endured mass bleaching events in 1998, 2002, 2016, 2017 and now in 2020. Experts predict that these events will become more frequent and more severe as global temperatures continue to rise, and the latest surveys of the reef will do little to allay those concerns.

The latest aerial surveys of the Great Barrier Reef, conducted by the ARC Centre of Excellence for Coral Reef Studies, have revealed that large areas of the reef have suffered high amounts of heat stress, and these areas have been subject to the worst bleaching. Some parts of the southern reef that escaped the bleaching of 2016 and 2017 have experienced moderate or severe bleaching.

Even corals leftover from parts of the reef badly damaged in the 2016 and 2017 events, which are thought to be relatively heat-tolerant, again were found to have undergone moderate and severe bleaching. The researchers note that key tourism reefs in the northern and central areas have suffered moderate bleaching, and they expect most of these corals to recover.

While bleaching is bad news for corals, it is not necessarily a death sentence, with those mildly or moderately bleached often having a good chance of recovery. But repeated bleaching events that are widespread and of great severity pose a real threat to ecosystems like the Great Barrier Reef, making it difficult for them to recover before the next wave hits.

The researchers expect this year’s event to drive a high coral mortality rate on the severely bleached sections of the reef. Director of the ARC Centre of Excellence for Coral Reef Studies, Professor Terry Hughes, took part in the recent aerial surveys and noted on Twitter that this is worse than past years, along with some more grim observations.

Source: Great Barrier Reef Marine Park Authority, ARC Centre of Excellence for Coral Reef Studies