Planet Earth (2006): Season 1, Episode 11 - Ocean Deep - full transcript

Open ocean, a vast biotope covering two thirds of the planet, some shallow, some as deep as the mountain ranges are high. The ocean has an immense, precariously complex food chain, varying ...

Away from all land

the ocean.

It covers more than half the surface
of our planet

and yet for the most part
it is beyond our reach.

Much of it is virtually empty

a watery desert.

All life that is here
is locked in a constant search to find food

a struggle to conserve precious energy

in the open ocean.

The biggest of all fish

thirty tons in weight,
twelve meters long

a whale shark.

It's huge bulk is sustained by
mere microscopic creatures of the sea


Whale sharks cruise on regular habitual routes

between the best feeding grounds.

In February,
that takes them to the surface waters

far from the coast of Venezuela.

Others are already here.

Baitfish have come for the same reason
to feed on the plankton.

The whale shark has timed it's arrival
exactly right.

Oddly, the tiny fish swarm around it.

They're using it as a shield.

Other predatory fish are lurking nearby.

Yellowfin tuna.
They seem wary of the giant.

The shark dives,
as if to escape from such overcrowding.

Now the tuna have a chance
to attack the unprotected baitfish

but then

back comes the giant.

It has taken a vast mouthful
of the baitfish itself.

Plankton, it seems,
is not the only food for a whale shark.

Both shark and tuna feast together

but the tuna must be wary.

Even they can end up
in the whale shark's stomach.

Predators here must grab
what they can, when they can

for such events do not last long.

The dense shoals, on which so many depend

gather only when water conditions are perfect.

Many predators spend much of their time
cruising the open ocean

endlessly searching.

Plankton feeding rays do so,
gliding with minimum effort.

The oceanic whitetip shark

another energy efficient traveler.

It specializes in locating prey
in the emptiest areas of the open ocean

patrolling the top one hundred meters of water.

Taste in water,
is the equivalent of smell in the air.

An oceanic whitetip is able to detect
even the faintest trace.

Small pilot fish swim with it.

The shark can find prey
far more easily than they can

and they'll be able to collect the scraps
from it's meals.

It's long, fixed pectoral fins

enable it to soar through the water,
with the least expenditure of energy.

This shark has found a school
of rainbow runners.

It would eat one, given the chance

but rainbow runners are swift and agile
and not easily caught

so, it bides it's time.

There's a chance that, eventually,
it may spot a weakened fish that's catchable.

The hunter

endlessly waiting.

Excitement far from land.

A school of dolphin
five hundred strong.

They've sensed there's food around,
and they're racing to catch up with it.

The news has spread.
Now a number of schools are on their way.

They're heading towards the Azores

volcanic islands
a thousand miles west of Portugal.

The dolphin scan the water ahead
with their sonar.

They're close to their target.

This is it.

Scad mackerel.

It's difficult for a single dolphin
to catch the fish.

To avoid wasting energy
the work as a group.

They drive the fish upwards,
trapping them against the surface

and there,
other predators await them.

Cory's shearwaters.

They're waiting for the dolphin
to drive the prey closer to the surface.

Now the shearwaters can dive down on them,
descending to twenty meters or more

and the dolphins block the baitball's retreat.

The dolphins leave
as soon as they've had their fill

and, at last, the mackerel sink below
the diving range of the birds.

As the Sun disappears,
a profound change takes place in the ocean.

Deep water plankton
start to rise from the depths

and another hungry army
prepares to receive it.

Every night,
wherever conditions are right,

countless millions of creatures from the deep
migrate to the surface, seeking food.

A baby sailfish,
fifteen centimeters long

snaps up everything in it's path.

In three years' time, it'll be one of the oceans
most formidable hunters

weighing sixty kilos.

Just now, however,
it's very vulnerable.

These manta rays are giants.

Eight meters across
and weighing over two tons.

The blade-like projections on either side of the head
help to steer plankton into the manta's mouth.

Dawn returns, and the plankton
sinks back into the depths.

If we are to follow,
we must use a submarine.

As we descend into the darkness,
the pressure builds, the temperature falls.

Below five hundred meters,
new, mysterious animals appear.

Their bizarre shapes help them
to remain suspended in the dark space.

Some resemble creatures
familiar from shallower waters

others defy classification.

All around, organic particles
drift downwards.

Marine snow, detritus from the creatures
swarming in the sunlit waters above.

The snow is food for many animals here,
like the sea spider

a small relative of shrimps and crabs.

Those strange leg-like appendages
are feathered, to stop it from sinking.

They can also enmesh marine snow

which it wipes carefully
into it's jaws.

A sawtooth eel
hangs upright and motionless.

Gazing ever upwards, it watches
for prey, silhouetted against the faint

glimmerings of light from the surface.

Days may pass before prey swims
close enough for it to strike.

Farther down still,
the blackness is complete.

No vestige of sunlight
can penetrate as far as this.

Food is very scarce and nothing
can afford to waste any energy.

A dumbo octopus simply flaps a fin

no need for the jet propulsion
used by it's shallow water relatives above.

The weirdest, in this world of the strange,

the vampire squid from hell.

Disturb it and it only retreats
a little distance.

Go after it,
and it has a special defense.

To see what it does,
you must switch off the lights.

The vampire squid
has lights of it's own.

Bioluminescent bacteria
shine from pockets on it's arms
to confuse it's predators.

Are those eyes?

In fact they're spots
at the end of it's mantle.

A bite there,
would leave the head unscathed.

The threat diminishes, and vampyroteuthis
disappears into the blackness.

At last,
the sea floor.

Over two miles down, the pressure here
is three hundred times that at the surface.

It takes several months for marine snow
to drift down as far as this.

As you travel away
from the rocky margins of the continents

an immense plain stretches ahead.

It extends for thousands of miles

gradually sinking downwards.

There are faint trails in the ooze,
signs that even here there is life.

These are what made some of them

sea urchins sifting the accumulating drifts.

Shrimps standing on elegant tiptoe

fastidiously select the particles
that appeal to them

but, in the deep sea, as everywhere else
if there are grazers, there are hunters.

A monkfish, almost indistinguishable
from the sand on which it lies.

Why waste energy chasing around,
if you can attract prey towards you with a lure?

Maybe that one was a bit big.

The monkfish can wait, for days if necessary,
until the right sized meal turns up.

Scavengers on the other hand,
have to move around to find their food.

Crabs can detect
the faintest of tastes in the water

and that helps them locate the latest body
to drift down from above.

Eels are already feeding on the corpse.

Isopods, like giant marine woodlice
a third of a meter long

are ripping into the rotting flesh.

Over the next few hours
there'll be frenzied competition

between scavengers of all kinds
to grab a share.

Just occasionally,
there is a gigantic bonanza.

The remains of a sperm whale.

It died five months or so ago.

There's little left but fatty blubber
clinging to it's bones.

It's flesh has nourished life
for miles around

but now the feast is almost over.

Spider crabs, a meter across,
still pick at the last putrid remains.

A few weeks more, and nothing
will be left, but bare bones.

The crabs will have to fast,
until the next carcass drifts down.

But not all food
comes from the sunlit world above.

The floor of the Atlantic Ocean is split in two
by an immense volcanic mountain chain

that winds unbroken
for forty five thousand miles around the globe.

In places, it's riven by great fissures,
from which superheated water

loaded with dissolved minerals
blasts into the icy depths.

Clouds of sulfides solidify into
towering chimneys, as tall as a three story house.

At four hundred degrees
this scalding cocktail of chemicals

would be lethally toxic
to most forms of life

but astoundingly, a particular kind
of bacteria thrives here

and feeding on the bacteria,
vast numbers of shrimps.

So, beyond the farthest reach
of the Sun's power

a rich independent community exists,
that draws all it's energy

directly from the Earth's molten core.

On the other side of the planet,
in the western Pacific bordering Japan

the dragon chimneys, another series
of hot vents, erupting in the darkness.

Here, more, but different bacteria
thrive in a similar way.

And here, too, more crustaceans,
but quite different species

from those around the hot vents
in the Atlantic.

These are squat lobsters,
clad in furry armor

jostling with one another
beside the jets of superheated water

for the best places,
from which to graze on bacteria.

These vents, too, like those in the Atlantic
are isolated oases

so widely separated,
that each community is unique.

Cross to the other side of the Pacific,
to the deep near the Galapagos Islands

and there are yet other fissures venting
superheated water.

One and a half miles down,
at a site known as Nine North

towering chimneys support
a spectacular display of giant tubeworms.

These vents
give off so much energy

that some of the worms reach
three meters in length.

They're the fastest growing
marine invertebrates known.

All told, over fifty different species
have so far been found living here.

The inhabitants of these bustling communities
may grow at speed

but their existence can also be short,
for the vents do not erupt indefinitely.

Suddenly, unpredictably,
they may become inactive.

Nine months have passed at Nine North.

What were only recently chimneys
teeming with life

have turned into cold,
sterile mineral monuments.

Some eddy, deep in the Earth's crust

diverted the volcanic energy elsewhere

and, an entire microworld was extinguished.

In places, volcanoes have erupted to build
great submarine mountains.

There are thought to be around
thirty thousand such volcanoes

some, measured from the sea floor,
are taller than Everest.

Sheer cliffs
soaring to drowned volcanic peaks.

Powerful currents
sweep up the mountains' flanks

transporting nutrients from deep water
towards the summits.

The hard rock provides excellent anchorage

for communities of great variety
and stunning color.

Soft corals, several meters across
collect the marine snow as it drifts past.

Whip corals stretch out into the current.

Giant sponges filter nourishment
from the cold water.

A richly varied community flourishes here

sustained by the nutrients and detritus
in the icy currents that flow around the peak.

Yet it is all blossoming
on an extinct volcano

a mile below the reach of the Sun.

A nautilus. It spends it's days
hiding four hundred meters down

But as night falls, it ascends
up to the reefs, to look for food.

It's graceful shell contains gas filled
floatation chambers, that control it's depth.

It's powered by a jet of water,
squirting from a siphon

but it travels shell first,
so it can't see exactly where it's going.

It's nearest living relatives
are squid and octopus

which, over evolutionary time,
have both lost their shells

and the octopus has become
one of the nautilus' major predators.

It's a master of disguise.

The nautilus keeps well clear of them.

It's small tentacles carry
highly developed chemical sensors

which can detect traces
of both predators and prey.

It uses it's water jet
to dig in the sand.

Because it devotes so little energy to swimming,
it only needs a meal once a month.

Got something. And just as well.
Dawn is approaching and it has to puff it's way

back, to deeper waters.

Thirty miles away, shoals of squid
are jetting upwards towards the surface.

By night, they seek small fish
among the plankton, but they're cautious.

Pacific spotted dolphin.

They're guided by their sonar.

The dolphin, as so often, are working
as a team, synchronizing their attacks

to confuse their prey.

As dawn approaches, squid and fish and plankton
retreat downwards, to shelter in the darkness.

Some of these isolated volcanoes

rise as much as nine thousand meters
from the sea floor, reaching close to the surface.

Around these peaks
invigorated by daily sunshine

marine life flourishes
in spectacular abundance.

Fish crowd here, because the volcano
forces nutrients to the surface

encouraging the plankton to bloom.

An oceanic wanderer,
a mola mola

stops by to be cleaned by reef fish,
at the sea mount edge.

Butterfly-fish pluck string-like parasites
from it's flanks.

The huge fish lives on jellyfish
over a thousand meters down

where the water is twenty degrees colder

so, a brushup near the surface,
allows it to warm up

before making more deep water forays.

The summit of this volcanic mountain
rises above the surface of the sea.

It's Ascension Island

eight hundred miles from any other land,
a welcome vital haven for long distance travelers.

Frigatebirds spend months
continuously airborne at sea

but at nesting time, they come to Ascension
from all over the ocean.

The island's barren slopes
of volcanic ash and lava

might seem to offer
perfectly good sites for a nest

but the frigates choose
an even more isolated site

Boatswain Bird Island,
a lonely pillar, just of Ascension's coast.

Frigates are the world's lightest bird,
relative to their wingspan

and they can soar for weeks on end
with minimal effort.

They seem much more at home in the skies,
than in a crowded colony on land

but nest, they must.

They come from all over the Atlantic
to this, their only colony.

There are boobys here, too.

To raise their young,
seabirds worldwide seek such remote islands.

Swimmers also come to Ascension to breed.

A female green turtle
approaches the coast.

She's not eaten once, in two months.

She may have traveled one thousand miles
from her feeding grounds

the greatest journey of her kind.

Many others are here, too,
resting on the sandy sea floor

awaiting the darkness of night,
when it'll be safer to visit the beaches.

Eggs that were laid a few weeks ago,
at the start of the season

are beginning to hatch.

Most hatchings happen at night.

Now, in the light of day,
the young are extremely vulnerable.

They must get to the sea as soon as possible

but their trials have only just begun.

Many will drown
in the pounding waves.

During the next twenty years,
the vast majority will inevitably die

but those that survive will, eventually,
as their mothers did before them,

return to the very same beach
where they were hatched.

How they find their way back

across thousands of miles of open ocean,
we still have no idea.

A frigate soars.

Somewhere, beneath the surface below,

there is the food it must have.

But where?

Those that fly above the ocean

must be able to read the signs
of fresh supplies, or perish.

A hundred miles from the Mexican coast,
and keen eyes have spotted movement.

Sailfish, three meters long,
are closing in on prey.

They will only use
just enough energy to make their kill

never wasting a fin stroke.

Nearly a hundred sailfish have surrounded
a single school of baitfish.

It's very rare to see so many
of these hunters in one place.

To herd their prey,
the predators raise their huge dorsal fins.

A mistimed strike by one sailfish,
could fatally damage another

but each continually changes it's color,
from blue, to striped, to black

that warns it's companions of it's intentions
and also confuses the prey.

As the shoal is driven nearer the surface,
it comes within the range of the seabirds.

Out here, in the open ocean,
there is nowhere for the baitfish to hide.

Sailfish live a high octane life.

To survive, they must find prey daily

so their entire existence will be spent
on the move.

Over ninety percent on the living space
for life on our planet, is in the oceans

Home to the biggest animal that exists

or has ever existed.

the blue whale.

Some weigh nearly two hundred tons

twice the size of the largest dinosaur.

Despite their great size, we still have little idea
of where they travel in the vast oceans

and none at all
of where they go to breed.

The largest animal on Earth
feeds almost exclusively

on one of the smallest
krill, shrimp-like crustaceans.

They take many tons of water into their
ballooning throats in a single gulp

and sieve out what it contains.

Every day, each one swallows
some four million krill.

Such gargantuan harvests depend
on the continuing fertility of the oceans

But global changes now threaten
the great blooms of plankton

on which the whales depend.

Once and not so long ago

three hundred thousand blue whales
roamed the oceans

now, less than three percent
of that number remains.

Our planet is still full of wonders.

As we explore them, so we gain
not only understanding, but power.

It's not just the future of the whale
that today lies in our hands

it's the survival of the natural world
in all parts of the living planet.

We can now destroy,
or we can cherish.

The choice is ours.