National Geographic: Ocean Drifters

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The human mind

has always had a fascination

with worlds beyond our own

Following the stars across the seas,

early explorers

imagined that they might meet

weird creatures in undiscovered lands.

They never guessed

that under their keels,

drifting in the same currents

that carried their ships,

were life forms far stranger

than anything they could imagine.

It's a world where the forces

of pressure and darkness

have given rise to creatures

as different as on another planet.

Their whole existence is shaped

by the great ocean currents,

which sweep them endlessly

around the biggest living space

in the solar system.

At the edge of this alien world,

here in Florida,

one ocean drifter comes

from the beach itself.

It can take these hatchlings three days

to claw their way up

from nests buried two feet deep.

They may look like land animals now,

but sea turtles have evolved

for 80 million years

to be riders of the ocean currents.

These loggerhead turtles,

no larger than a child's hand,

are about to embark on a perilous

As they head down the beach,

they're already reading

the earth's magnetic field

with their internal compass.

Only one hatchling in a thousand

will survive to adulthood

and ride the currents back to

this beach to breed.

It's among the most extraordinary

odysseys in nature.

This is the story of one loggerhead's

journey into the unknown world

of the ocean drifters.

Like a windup toy, the hatchling swims

relentlessly out into the ocean.

The waves tell her which way to go

away from shore and from

predators stalking the shallow water.

Danger causes her to tuck in her limbs

disguising herself as floating debris.

The shark doesn't see her and swims on

As she heads toward the safety

of deep water,

the hatchling joins a rich tide

of other marine creatures.

Every rock and weed is home to

a different species.

Coastal waters are the fertile

breeding ground for the oceans.

Florida may produce five million

loggerhead hatchlings each year.

In some coastal species,

from a single female.

The eggs of this sea urchin

and the smoky clouds of sperm

from a nearby male

swirl together in a fertility dance

on the ocean floor.

Huge quantities of eggs and

larvae produced along the coastline

will be drawn into the ocean currents.

Most will become food

for other marine creatures.

Setting their offspring adrift

might not sound like good

parental care.

But it's a valuable survival mechanism

for many coastal species.

It lets them populate new areas

and encourages the exchange

of genetic material.

All through the night, instinct

drives the loggerhead to push on.

The outpouring of new life

on the continental shelf below her

is just as persistent.

With the bellows like action

of her pleopods,

the spiny lobster sends

It's a reproductive blizzard.

The lobster's larvae have evolved

a flattened shape;

it suits them for the drifting life

as ideally as a snowflake.

After 36 hours of swimming,

the hatchling is growing tired.

In the clear water 30 miles off

the Florida Coast,

she reaches the edge

of the Gulf Stream,

and finds shelter in the drift lines

of sargassum weed.

This plant spends its

whole life floating on the open sea,

held up by small air bladders.

The sargassum provides a haven

in a vast, featureless world.

All kinds of creatures

find harbor here.

For the first time in her life,

the loggerhead can rest.

But the stillness is an illusion.

The winds have piled up the sargassum

weed in drift lines

along the edge of one of the most

powerful currents in the world.

Just beyond,

the Gulf Stream hurtles by.

Viewed from space, the Earth is alive

with clouds caught up in the rhythm

of the tradewinds.

These winds

and the rotation of the planet

generate the great ocean currents.

The loggerhead will be traveling

for years

in a circle of currents called

the North Atlantic gyre.

Her journey starts off Florida

in the warm waters of the Gulf Stream,

which will carry her

north past Cape Cod.

Satellite imagery is teaching us

that the Gulf Stream

is a wild living carousel,

spinning off side currents,

and stirring up a broth of marine life

The edges of currents are the

great way stations of the open sea.

Plant and animal drifters are drawn

into these fronts,

one species making life possible

for another.

For a hungry animal,

it's an oasis in an oceanic desert.

The sargassum becomes a perch

for goose barnacles.

They glean food particles

from the plankton,

the rich soup of plants and animals,

many of them microscopic.

Even sluggish homebodies

can be marvelously adapted for travel

in the larval stage.

The glorious creature drifting

on wing-like lobes is a snail.

Some snail larvae use tentacle

like arms

for feeding and to keep from sinking.

Some may by able to remain

in this stage from months

until they drift to a suitable habitat

Everything is kept lightweight

for easier travel.

Look closely and you can see

the spiral of a transparent shell.

These beautiful drifters move

so gracefully,

you forget that the Gulf Stream is

hurrying them along at 100 miles a day

Microscopic larvae spawned in Florida

could eventually settle

on the shores of Africa.

And the next generation

may ride the currents back.

The ocean drifters have little to eat

except each other

which they do eagerly.

So if the sargassum weed

provides shelter,

it also harbors death

in an astounding diversity of forms,

often wonderfully camouflaged.

The sea horse has evolved

a mild and plant-like demeanor.

But it's still a predator

and keenly watchful.

It drops down to ambush

its planktonic prey.

Then loops itself back

into the sargassum

to avoid being ambushed itself.

The entire food chain is caught up

in this dangerous game

of deception and self-defense.

Small fern-like animals known

as hydroids

colonize the sargassum

and feed on the most minute plankton.

A sea slug grazes in turn on hydroids.

The slug's camouflage doesn't fool

a potential predator.

But the sea slug has armed itself

with chemical defenses from its prey.

The file fish abandons the attack.

But another creature's camouflage

will soon bring the fish to a gory end

The drifting weed may look innocuous.

But look again.

A fish hoping to harvest hydroids

from this leafy growth

would find itself staring

into a malignant eye.

Evolution has made

the four-inch long sargassum fish

the big bad wolf

of this floating world.

Its extraordinary camouflage doesn't

just mimic the coloration of the plant

The white spots also mimic

the tube worms

and hydroids that grow on sargassum.

Its pectoral fins have evolved

into prehensile fingers,

the better to creep through

the foliage.

It will eat creatures

almost its own size,

and its victims thrash around

in its gut momentarily before they die

The loggerhead swims directly

under this hidden peril.

But the sargassum fish

lets her pass by.

Hungry dolphin fish

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