This is scientific American 62nd Science. I'm Julia Rosen. Got a minute?

The Maldives form a constellation of almost 1,200 coral reef islands in the Indian Ocean.

They have stunning white sand beaches surrounded by emerald blue water, and according to a new study,

they may owe their existence to parrotfish, more specifically to parrotfish poop. If you've ever snorkeled near a coral reef

you've probably seen neon-colored parrotfish. Their name refers to their sharp

beak-like teeth. You may have heard them too. That's a parrotfish literally

eating the reef's coral skeleton. It bites off tiny pieces of hard coral as it forages for algae. That gets taken into the fish. It's then milled and it

passes through their intestines and it's then excreted out the back end as clouds of sediment.

Chris Perry, a marine geoscientist at the University of Exeter in the UK.

And that is then distributed onto the reef and is a way, at least in this system and elsewhere where parrotfish

are abundant that you can convert coral substrate into sediment grade material.

In 2013 Perry and colleagues went to the Maldives to find out how the reef, which grows underwater,

generate sediments that pile up forming islands that rise above the water's surface.

The team discovered that parrot fish play a critical role in this

process. Their waste accounts for a whopping 85% of all the sand produced on the reef.

You know, if you spend time on the reefs and you're following the parrotfish around it's absolutely incredible how how much sediment they're

producing so when you've got large populations of them they can be very important in

this respect. The new results suggest that protecting parrotfish populations is essential for maintaining the Maldives, which already face threats from rising seas.

If you take the parrotfish out of these systems, you would basically be shutting down a very significant amount of the sort of supply

chain for island building sediment.

By the way, the beautiful white sand beaches in parts of Hawaii also largely parrotfish

poop.

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