This is Scientific Americans 60 Second Science. I'm Jason Goldman. Got a minute?

In April, the world learned that more than 90% of Australia's great barrier reef had become bleached.

Warming waters or other conditions caused the algae living inside the coral to exit,

leaving the coral weak.

It's a bleak statistic because it's reasonable to assume that as the corals

themselves suffer, the entire ecosystem they support suffers as well. For example, a study

finds that bleaching hinders fish from learning to avoid predators.

Imagine you're a fish, and suddenly one of your friends meets its unfortunate end in the jaws of a predator.

We found that these animals actually have this really sophisticated way of learning,

which involves the linking of chemical alarm cues, which damage release cues from

constellistics, and any other smell or even the sight of anything

novel, sort of Pavlov to dog type scenario.

James Cook University Marine Scientist Mark McCormick.

He and his team found that this learning process breaks down when the coral becomes bleached.

Instead of hosting algae within, the bleached coral becomes blanketed by algae.

We've used little patches of live coral and little patches of dead and degrading coral,

which has similar topographic complexity.

And what we've done is we put those little patches

within a bed of even live coral or dead and degraded coral.

On to each patch the researchers deposited a small naive reef dweller called a damselfish.

They wanted to see how the health of the reef influenced the fish's ability to learn to

avoid the odor of a predator called the dusky dotty back.

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