♪ (narrator) This seagrass meadow sways with the tides.

Peek closer, and you'll find a humble and hypnotic character, the eelgrass sea hare.

It's a kind of sea slug, but looks more like a slice of zebra-striped jello.

A sea hare gets its name from its ear-like rhinophores, the two tentacles on top of its head.

If you look at them in just the right light, you may even see that bunny resemblance.

It uses its rhinophores to sense water movement, temperature, and even smell, like if a potential mate is nearby.

To get fresh oxygen, the sea hare pumps water through gills tucked under these foot flaps called parapodia.

The eelgrass sea hare lives off the Pacific Coast of North America and dwells almost exclusively on-- you guessed it-- eelgrass.

It's a type of marine grass that grows at the edges of oceans.

Scientists believe the two evolved together over millions of years.

The sea hare grazes constantly, all day, every day.

But it doesn't eat the grass.

Using its radula with rows of petal-shaped teeth, the sea hare actually scrapes the grass for the microscopic algae that coats it.

Slurping up the algae on the eelgrass lets more sunlight hit the plants so the meadows can keep growing.

Seagrass meadows help control erosion and absorb carbon from the atmosphere.

Also, they make some sweet digs for all kinds of creatures.

Oh, hello.

But like old-growth forests and coral reefs, seagrass ecosystems are rapidly disappearing.

So were the eelgrass meadows of this wetland, Elkhorn Slough.

For decades, fertilizers from farms drained into the water, overfeeding the algae.

Massive algal blooms blocked the sunlight from reaching the grasses, and there was another problem.

Sea otters were missing.

We hunted them for their fur, almost to extinction.

The whole system was out of whack.

The grasses started to die.

But in the 1980s, scientists reintroduced sea otters here and things improved.

That's because sea otters eat the crabs that eat the sea hares.

Fewer hungry crabs means these slug bunnies are back in business, once again eating algae so this eelgrass can flourish, even with extreme algal blooms.

This is called a trophic cascade, when a top predator like an otter helps to keep an ecosystem in balance.

A healthy eelgrass meadow also means a haven for the sea hares' eggs and protection for its young, the next generation of this habitat's tiny, slimy stewards.

Hey, it's Laura.

Don't go yet; there's lots more mollusks where that came from.

Just slide into our delightful mollusks playlist.

It's filled with slugs, squid, octopuses, snails, nudibranchs, and even mussels.

Enjoy.