Into the Deep

From a distance, they look like shadows on the water.

The ones we're approaching lie just along the California coast.

There's a forest under here, and these are the tops of its trees.

This is a forest of giant kelp:

The largest plants in the ocean...

... as tall as office buildings.

On the surface, trees this tall would need rigid trunks.

Not the giant kelp.

Tiny floats along each stem are enough to hold it up.

It is anchored to the ocean floor by a root-like structure called a holdfast.

No nourishment is provided through the holdfast.

All nutrients are absorbed directly from the water itself.

Every habitat on earth has evolved its own village of relationships...

... its own citizens.

All sharks sink unless they swim.

This female swell shark has settled here for a purpose.

Every few months she lays a single egg.

Ten months later, helped by little hooks on its back...

... the baby swell shark will struggle from its case.

This is the approach to life his species has evolved:

They begin it alone.

This fiery little sentry is a garibaldi.

The nest he's guarding is that dark patch on the side of the rock.

Moray eels have powerful, crushing jaws and sharp teeth...

... but they are not a threat to the garibaldi. The prey they lie in wait for is octopus.

The octopus has blundered into the garibaldi's nest.

Morays stalk their victims not by sight, but smell.

That squirt of ink contains an anesthetic that foils the moray's sensitive nose.

Like a banner on a castle wall, the dazzling garibaldi posts himself...

... on his ramparts, a guard whose watch is never done.

He protects his nest from hungry fish and scavengers.

Sea urchins are a constant annoyance.

It's the male garibaldi who makes the nest...

... nibbling it neatly out of a patch of algae.

He ends up with a space about a foot and a half across.

This nest already has eggs in it, but if the male keeps things tidy...

... he may still attract another female.

When he sees her, he goes straight to the courtship acrobatics.

Each time he does a loop, he clucks twice.

The courtship worked.

The female is laying eggs.

From time to time the male moves in to fertilize the eggs.

Since the female will eat the eggs if she gets the chance...

... her fierce little partner chases her away as soon as the laying is done.

In a couple of weeks a swarm of tiny garibaldi will drift away on the current...

... to join the ebb and flow of other new life in the underwater forest.

Many will be caught and consumed by animals like this tube anemone...

... a creature that snares its food in a thicket of stinging tentacles.

Others will escape to a great living mass of minute plants and animals...

... called ocean plankton.

But even there they are still food.

The pelagic jellyfish harvests them with a paralyzing sting.

The face of an escarpment below the kelp forest.

These corals look like plants, but they're animals.

Their branches comb the passing current for plankton.

Deeper, lies an even stranger world:

A vast shag carpet of diminutive starfish known as brittle stars.

A sheep crab gallops clumsily across the brittle star garden.

Is this kelp crab about to make a meal of his captive?

No. The larger crab is a male.

He shelters and protects the female who is carrying a brood of eggs.

These sarcastic fringe heads...

... yes, they are called sarcastic fringe heads...

... have moved into adjacent empty shells.

The trouble is they're both males.

In the face of threats like these, one will have to leave...