Understanding the human body is a team effort. That's where the Yachtel group comes in.

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This is Scientific Americans' 60-second science. I'm Jason Goldman. Got a minute?

Predators like wolves affect their ecosystems by eating their prey. But a more subtle impact involves fear.

Predators also terrify prey species. And when, for example, elk are hiding, they don't spend as much time eating leaves.

The impact of a predator down through the food web all the way to plants is called a trophic cascade.

Meanwhile, fish at a coral reef near the Fiji archipelago in the South Pacific generally graze on the

seaweeds that grow on the reef.

But when reef sharks emerge from deeper waters, it's best to quit foraging and hide instead.

And thinking about these other ecosystems like wolves, their effects in their ecosystem

don't play out in all places at all times. They happen to be most pronounced in risky habitats,

like river valleys or gorges. Marine scientist Douglas Rasher from the nonprofit Bigelow Laboratory

for Ocean Sciences in Maine. So it got me thinking that maybe these shallow habitats might be the

place where sharks have their most pronounced

effects on the ecosystem.

At one time, researchers did not think troughacquescades even existed in the real world,

and many still debate whether sharks can drive trophic cascades on coral reefs.

By observing reef communities in Fiji's Votua Marine Reserve, Rasher and his team discovered that sharks

do in fact influence plant growth on the reefs, by scaring the herbivorous fish away from eating

...