Great Barrier Reef bleaching kills millions of marine animals

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While diving in Thailand in 2010, Mark Eakin, a NOAA scientist, saw clownfish behaving in strange ways – and for very concerning reason.

Clownfish live in sea anemones – jellyfish-like polyps with poisonous tentacles – primarily for safety reasons. But the clown fish he had seen had stopped doing that.

“Instead of rushing into their anemone for safety’s sake, the anemonefish would go to nearby bleached corals because something was wrong with their anemones,” Eakin told The Dodo. “They no longer saw it as a safe house.”

The anemonefish changed their behavior immediately after massive coral bleaching occurred in the area. Coral bleaching occurs when the sea temperature rises and the corals expel the algae living inside their tissues, making them white.

This sort of thing is happening all over the world, and now it’s hitting the Great Barrier Reef in Australia, the largest coral reef system in the world. And that’s bad news for the marine animals that depend on the reef.

Aerial view of bleached coral on the Great Barrier Reef | Arc Center of Excellence

In 2016, 67% of the northern Great Barrier Reef region died. This year, more bleaching has occurred, although scientists are still determining how serious it is. Unfortunately, some fear the worst.

“The severity of the 2016 bleaching was out of this world,” said Terry Hughes, director of the ARC Center of Excellence for Coral Reef Studies, in a statement. “This was the third major bleaching to affect the Great Barrier Reef, following previous heat waves in 1998 and 2002. Now we are preparing to look at potential number four.”

Bleached coral on the Great Barrier Reef in Australia
Bleached and dead coral on the Great Barrier Reef | Arc Center of Excellence

When coral reef systems die, animals lose their homes. Not just a few animals – millions of them.

Bleached coral on the Great Barrier Reef in Australia
A fish swimming next to dead, bleached coral | Arc Center of Excellence

“You are losing countless different species – small organisms, vertebrates and reefs,” Eakin said. “And of course the fish communities are affected. They just left.”

Bleached coral on the Great Barrier Reef in Australia
A scuba diver surveys damaged corals on the Great Barrier Reef | Arc Center of Excellence

Where exactly are they going?

Bleached coral on the Great Barrier Reef in Australia
Arc Center of Excellence

“That’s a really good question,” Eakin said. “Some of them die… of starvation or predation. They stop behaving as they normally do, and they are more susceptible to predators.”

Bleached coral on the Great Barrier Reef in Australia
Arc Center of Excellence

Other animals may try to move elsewhere, but this is not always the best option.

“When the reef dies and becomes covered with algae, they leave and move elsewhere to other habitats nearby,” Eakin said. “But they won’t do as well and could be subject to more predation.”

Bleached coral on the Great Barrier Reef in Australia
A fish swimming next to dead, bleached coral | Arc Center of Excellence

The problem of coral bleaching may seem impossible to solve, but there are things we can do. To help marine animals keep their coral reef homes, you can donate to the Great Barrier Reef Foundation.


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