National Geographic: Ocean Drifters Page #3

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are already being used in medicine.

But reaping the potential benefits

is dangerous work.

In many ways, it's like the grand

adventure of space travel.

But we've mapped the barren surface

of Venus in far more detail

than our own deep ocean floor.

Is it worth exploring the depths

of this planet?

In one area the size

of a small living room,

deep sea researchers recently

discovered 460 new species.

Who knows what secrets

we have yet to discover in the oceans?

Even back on the surface,

the limits of our knowledge can be

painfully apparent.

In the complex ecosystem

at the very skin of the ocean,

a whole other world of creatures

lives both in and out of the water.

As it moves, the stinging tentacles

of the Portuguese man o' war

stream out to gather food.

By raising its gas-filled sail,

the man o' war can travel

at varying angles to the wind.

It's an elegant system

for dispersing animals

not just where the current takes them,

but across the face of the ocean.

Nothing about the man o' war is simple

It's neither an individual animal,

nor a colony, but something in between

Joined together under the gas bladder

is a kind of cooperative assembly

of stomachs,

tentacles, and reproductive organs.

Other species add to the complexity.

One fish, called nomeus,

hides out among the deadly veil

of tentacles.

The man o' war toxin is

more potent than the cobra's.

But perhaps because

of a protective mucus layer

or greater immune resistance,

nomeus can dine unharmed

on the man o' war itself.

Other fish aren't so lucky.

The man o' war can stretch

its tentacles out more than 50 feet,

and each tentacle is studded

with batteries of stinging cells.

Nomeus may help out the man o' war by

herding these fish toward their death.

Triggered by the fish,

the stinging cells fire slender

threads lines with barbs.

The victim is lassoed, hog-tied,

and injected with paralyzing poison.

Then the digestive organs move in.

Like some monstrous lifeform,

they wriggle and twist

as they fasten their flexible mouths

onto the victim.

Gradually, they engulf the fish

and dissolve its flesh.

After half a year,

the young loggerheads odyssey

has taken her to mid-ocean.

But she still has a lot to learn.

All the activity around

the man o' war catches her eye.

She just wants to grab

a few fishy tidbits

and doesn't seem to notice

the nasty business overhead.

For a moment, the turtle looks like

a puppet on a deadly set of strings.

But it's the man o' war

that's in danger.

The turtle turns her hungry eye

on this intriguing new possibility.

People talk about the first

brave human who ate an oyster.

But what a tangled and spicy meal

the man o' war must make.

The turtle's skin may be too thick

for the stingers to penetrate.

But no one knows what protects

the turtle's eyes and mouth.

The loggerhead soon pushes on

in search of a meal

that's not quite so challenging.

One of the strangest inhabitants

of the harsh world

between air and water is the drifting

nudibranch named glaucus.

This upside-down sea slug swallows air

bubbles to hold itself at the surface.

With its pointy appendages,

it latches onto anything

it's lucky enough to bump into.

But what it's really after are

the deadly tentacles of the man o' war

It coats its mouthparts

with a mucus layer to protect itself.

The smaller less powerful

stinging cells get digested.

But the most virulent stingers

remain intact.

Amazingly, they pass directly

to the nudibranch's extremities

and it uses them for its own defense.

But these surface drifters

must face adversaries even more

formidable than each other.

A storm is brooding up

across the water.

It's a reminder of how unstable life

must be on the very face of the ocean.

One moment these creatures are

being scorched by sun and wind,

and the next they're tumbling

in storm-tossed waves.

As the storm passes,

they get pelted by icy rain

and have to endure the dilution

of their salty home.

Yet the animals living in

the ever-changing surface

can seem so delicate.

This drifting snail

builds a fragile home of air bubbles

sealed in an envelope of mucus

then hangs on for dear life.

If it lets go,

it'll sink into the abyss.

The raft is also holding up

the snail's offspring,

in these egg capsules.

It's a cradle at the top

of a hostile world.

When it's done laying eggs,

the snail builds a new raft for itself

and cuts its 50,000 offspring adrift.

Natural debris also drifts

in the surface currents.

It's always been a means of dispersal

for some plants.

A coconut from the Caribbean

may ride the Atlantic

currents thousands of miles

to take root on some distant shore.

Fish are drawn to this kind

of flotsam for shelter.

A drifting crate can turn

into a small ecosystem,

Where fish lay eggs

or find their food.

But the little things

we throw away add up,

and the supply of garbage begins

to seem endless.

One study estimated that

was being heaved overboard

by ocean-going vessels alone

A recent treaty now regulates

the practice,

but it's rarely enforced.

Whatever goes into the ocean

gets drawn into the currents,

and it builds up in the very places

where marine life is richest.

Animals encrusted on debris may rouse

the loggerhead's hunger and curiosity.

For her, drifting objects have always

been a natural food source.

Until recently, a loggerhead could safely

eat almost anything she came across.

Nothing in her evolution

has prepared her

for this wealth of deadly new choices.

To her, it makes as much sense to pick

at the festive remnants of a balloon

as at a man o' war.

Fragments like these

can choke turtles to death.

Plastic blocks their digestive tracts

and causes starvation.

This time, she's unable to

tear off a bite.

But she'll face many more

opportunities as she swims on.

Almost every dead turtle found

has plastic in its gut.

Millions of seabirds also die

each year because of garbage

like this gannet tangled up in debris

absent-mindedly discarded

by sportfishermen.

Commercial fishermen lose thousands

of miles of net each year,

which spread out all across

the oceans like a deadly web.

There may be no way for the loggerhead

to learn about these new perils

until it's too late.

The turtle has survived her first year

But in the long seasons before she

circles home to Florida to lay her eggs

a more sinister peril may threaten her

Everything out here

is absorbing a swelling tide

of chemical wastes

even the plankton.

Though they may seem insignificant,

the lifeforms here are important

to cloud formation.

They even help regulate

the global climate.

These microscopic plants and animals

have always struggled against

enormous odds to reach maturity

Now they must also absorb heavy metals

sewage, pesticides and petrochemicals.

Plankton is the base of the food chain

and every marine animal depends on it.

If our carelessness disrupts this vast

drifting tide of life,

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