The Great Barrier Reef Is About To Face Its Third Major Bleaching Event In Five Years

Great Barrier Reef after the 2016 rise in ocean temperature leading to a mass coral bleaching event. Darkydoors/Shutterstock

Rachael Funnell 10 Mar 2020, 20:15

The 2019-2020 Australian bushfire season, known as the Black Summer, caused unprecedented damage as it burned through 18.6 million hectares of natural habitats. But as the devastation on land has slowed, now Australia’s marine ecosystems are facing a crisis as an update from the National Oceanic and Atmospheric Administration’s Coral Reef Watch predicts the Great Barrier Reef is about to undergo its third major bleaching event in the last five years.

Healthy coral systems are populated with symbiotic algae that maintain the health of the coral and the reef as a whole. When bleaching occurs, the corals expel these beneficial algae, stripping the reef of its color and leaving behind sparse white skeletons of the remaining coral. Bleaching events are triggered by extreme heat and ocean acidification, both of which have been linked to climate change.

In recent years, the Great Barrier Reef has experienced more than its fair share of coral bleaching, with the longest ever coral bleaching event being recorded at the reef in 2016. Reports from the National Oceanic and Atmospheric Administration’s Coral Reef Watch predict it's soon to face another widespread bleaching event, threatening the stability of the world’s largest reef system.

In January of this year, sea surface temperatures were recorded at 1°C (1.8°F) higher than usual which, when combined with forecasts for warm weather on dry land, are likely to crank up even higher. This spike in ocean temperature is going to place the reef under stress and the Coral Reef Watch predicts that level 2 bleaching will hit the entire length of the Great Barrier Reef.

While it’s not currently expected that the bleaching event will be as severe as those seen in 2016 and 2017, it's predicted that the widespread bleaching will cause significant mortality, throwing into question the reef’s capacity to bounce back following such a swift burst of setbacks in the last five years.

Each time a bleaching event occurs, fast-growing coral species start to repopulate the reef. While this helps to maintain the structure and health of the reef, fears are growing among environmentalists that diminishing biodiversity could threaten the stability of the ecosystem and its capacity to mitigate future crises. A recent review from researchers at Bangor University, Southampton University, and The School of Oriental & African Studies, University of London, concluded that ecosystems with fewer interacting species were far more likely to be lost and at a faster rate than those that were made up of a rich diversity of influential species.

Much like the Amazon rainforest, the Great Barrier Reef serves a vital environmental function as a carbon sink thanks to its vast meadows of deep-water seagrass. If rising sea temperatures cause it to collapse, we can’t be certain what sort of ecosystem would replace it, and if this vital carbon sink is lost, then CO2 levels will continue to rise even faster than the current rate.

Find out why one tiny territory may hold the key to helping bleached coral systems to recover.

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