Coral bleaching is killing the Great Barrier Reef - here's how

Large parts of the Great Barrier Reef are dying because of a process known as coral bleaching.

While some areas are unaffected by bleaching events, they are happening more frequently, leading to concern about the Reef's survival.

It's not just Queensland that is affected, across the world, these amazing, biodiverse underwater habitats are stressed and sick - here's why.

Left - Bleached coral. Right - Fish swimming near coral
The Great Barrier Reef suffered a significant bleaching event in 2020. Source: Getty/Reuterss

When did the bleaching first start to occur?

The world's first mass bleaching was recorded in the 1980s, however these events have been occurring more frequently over the last two decades, leaving coral without time to recover.

In 2020, the Great Barrier Reef experienced its third major bleaching event in just five years.

What is coral bleaching?

Corals are home to microscopic algae called zooxanthellae which live within their tissue and cause them to appear brightly coloured.

When ocean temperatures rise by as little as one degree Celsius, coral can become stressed and expel the coloured algae. It then appears to be bleached white.

A diver near a large brain coral in Indonesia.
Coral bleaching has affected reefs around the world, including this site in Indonesia. Source: Getty

While "bleaching" does not immediately kill the coral, without the algae it loses a major nutritional source, and this often results is disease and ultimately death.

Warming waters as a result of climate change is a key driver of bleaching, but low tides, agricultural runoff, and too much sunlight are some of the other known causes.

Bleaching by the numbers

  • During 2020, it is estimated that 25 per cent of the Great Barrier Reef experienced severe bleaching.

  • An additional 35 per cent was moderately bleached.

  • Bleaching in 2020 was not as destructive as the 2016 event, but was worse than 1998, 2002 and 2017.

A chart showing how coral bleaching occurs.
How coral bleaching occurs. Source: NOAA

The reason coral reefs are important

Coral reefs are home to thousands of marine creatures including fish, sea turtles, sea birds, crabs and jellyfish.

Humans are affected too, because when reefs die and food webs are broken, industries like fishing and tourism begin to crumble.

More things you might want to know about our oceans

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