All language subtitles for A.Perfect.Planet.S01E04.2160p.Oceans.Remux.HDR10.HEVC.TrueHD.7.1_Track04_PGS

DAVID ATTENBOROUGH: A Perfect Planet.

All life in the oceans depends
on the continuous movement of water.

There are not five separate oceans
on Earth,

but just one...

...whose parts are linked by
powerful, unceasing currents.

Every drop of seawater on Earth
rides these currents,

taking a thousand years
to complete a single circuit.

And where there are currents...

...there is life.

Off the coast of South Africa,

dolphins are on the hunt.

They have found a cold-water current

and are now travelling along it
looking for food.

Gannets follow them.

They know that doing so
is the fastest way to a meal.

A shoal of mackerel -

just what the dolphins
have been looking for.

They encircle the fish,
driving them into a bait ball,

and then trap them against the surface

to prevent them from escaping
to deeper water.

Now the fish are within range
of the dive-bombing gannets,

who hit the water at 50 miles an hour.

A sudden gathering of thousands
of predators brought together

by the flow of currents.

Last to the feast are sharks.

In these vast open waters,

finding food would be all but impossible
without currents,

the highways of the seas
that bring this life together.

When the bait ball has been dispersed,

all that is left are scales
drifting downwards.

They are part of a slow,
never-ending blizzard of organic waste

that eventually settles on the sea floor.

But it doesn't stay here for ever.

The currents sweep it back up
into the sunlit surface waters...

...where it nourishes
clouds of phytoplankton...

...simple microscopic plants
that are the pastures of the seas.

There are thousands
of different kinds,

and together they produce half
of all the oxygen in the atmosphere...

...more than all our forests
and jungles combined.

And by absorbing carbon,

they are our greatest ally
in combating climate change.

Plankton are the foundation
of almost all life in the ocean,

for in those places where the currents
bring nutrients to the surface,

they multiply in astonishing numbers...

...turning the ocean green.

The currents travelling through our oceans
bring life to seas

that would otherwise be marine deserts.

The Galépagos Islands lie
in the path of one of them,

the deep-flowing Cromwell Current

that runs for 6,000 miles
across the Pacific.

As it approaches Fernandina Island,

it rises and delivers nutrients
into its shallows.

And it also brings life
to this otherwise barren island.

Iguanas.

There are thousands of them.

And yet there's nothing on the island
for these vegetarians to eat.

Or...

...almost nothing.

Cormorants bring seaweed ashore
with which to make their nests.

But what is building material
for a cormorant

is food for an iguana.

(SQUAWKS)

Both these species evolved here,

but that doesn't necessarily make them
good neighbours.

No matter.
He knows where there's more elsewhere.

He's a marine iguana...

...the only lizard in the world

that gets its food from the sea.

The seaweed on which he totally relies

only grows in abundance here

because of the nutrients
brought by the Cromwell Current.

Once in the water,
he has just 30 minutes to find food.

Any longer than that,

and his muscles will seize up
and he'll drown...

...for, like most reptiles,
he can't handle the cold.

Chilly water isn't a problem
for a warm-blooded cormorant.

She can swim in it all day,

but can only hold her breath
for a few minutes.

He, on the other hand,

completes his whole half-hour trip

on one single breath.

His flat face and sharp teeth

make him an efficient
seaweed-cropping machine,

but with the clock ticking,
he must eat fast.

The cormorant, having caught its fish,

goes back to the surface.

One last mouthful,

and it's also time for the iguana
to head for home.

But to stop his muscles from seizing up
in the cold water,

he must get back quickly.

So he could do without the attentions
of an inquisitive sea lion.

Dry land is now just 30 metres away,

but the biggest hurdle is still to come.

The surging water now fights against him.

He's out,

but he stayed in the cold so long
that he's lost his strength.

And he's made it.

Few reptiles on the planet have
to work harder for a meal than he does.

And tomorrow,

he'll have to do it all over again...

...unless next time

he can outwit his neighbour.

Over 100,000 marine iguanas
live on Fernandina...

...and each owes its existence
to the Cromwell Current

that brings nutrients to these shores.

But there is another, much bigger current

which carries water from the Pacific
into the Indian Ocean.

On this great journey, it travels
through the islands of Indonesia,

bringing together life
from both oceans.

A third of all the world's reef fish
live here.

Some call it the Coral Triangle,

the most diverse marine region on Earth.

The variety here is dazzling,
not just of coral,

but of animals of all kinds.

Few are stranger
than the flamboyant cuttlefish.

This is a male,
just five centimetres long.

Swimming against the current isn't easy
when you're small,

so, instead, he prefers to walk...

...very, very slowly.

He's a master of camouflage.

But right now he wants to be noticed.

He's looking for a mate.

His potential partner
is a giant by comparison,

four times his size.

When it comes to courtship,

being flamboyant isn't enough.

To win her over, he must dazzle.

His aim is to deposit a packet of sperm

inside her mouth.

Close...

...but no cigar.

He'll have to turn up the dazzle.

Take two.

Bingo!

His job is done.

Now she must find somewhere
to lay their eggs.

An old shell will do nicely

if she can slip past the present occupant.

She fastens her eggs
to the underside of the shell,

where they'll be safe from predators.

The current that brings so much life
to the Coral Triangle

now washes the eggs
with clean, oxygenated water.

After just three weeks,

they start to hatch.

Smaller than a human fingernail,

the hatchlings are now carried
by the current

to other parts of the reef.

And in just a few months,

this young male will be ready
to find a female of his own.

By a stroke of cosmic good fortune,

the Earth has a satellite,

the moon,

which orbits our planet every 27 days.

Its gravitational pull
drags our oceans across the planet...

...and so gives us the tides.

Unlike currents that stir the open ocean,

the tides have their greatest impact
on the coasts,

flushing them with nutrients
from both sea and land.

And nowhere are they more violent
and dramatic than here...

...Norway's Saltstraumen strait.

Every six hours,

nearly half a billion tonnes of water

are forced through a channel

just 150 metres wide.

Its very narrowness
accelerates the water...

...making this the strongest tidal pull
in the world.

Most animals caught here
would be swept away.

But not these tidal specialists.

Eiders are one of the few ducks

that depend totally on the ocean

for their survival.

And they're the only kind strong enough

to live permanently
in these racing waters.

But there is food here,
and in great quantity,

for any that can gather it...

...mussels.

They filter out particles of food
brought to them by the tide.

And eider ducks love mussels.

The challenge is reaching them.

Eiders seem to be the only creatures

that can hold their own
in the fast-flowing water...

...so they have the mussels
all to themselves.

They swallow them whole, shell and all.

Each eider duck
eats hundreds of mussels a day...

...a year-round feast

that no others can reach.

The tides here owe their power

to the unique geography of the coastline.

But elsewhere in our oceans,

the lay of the land influences tides

in a very different way.

Here in the Bahamas,

wide, shallow sandbanks
mean the tide moves gently

over the sea floor...

...turning what would be a sandy desert

into a rich underwater habitat.

This is the home
of garden eels and razor fish.

And fresh food arrives for them
from deeper waters twice a day.

Life seems unhurried and gentle...

...but there is trouble in paradise.

(WHISTLING AN D CLICKING)

These bottle nose dolphins eat razor fish,

and they're not so easily fooled
by vanishing tricks.

They scan the sand
with echolocating clicks

to discover exactly
where the razor fish are hiding.

(CLICKING CONTINUES)

But knowing where they are
is not the same as catching them.

The more the dolphins dig,

the deeper the razor fish burrow.

But it's clearly not deep enough.

Blowing jets of water into the sand

exposes even
the most hard-to-reach razor fish.

Before long, the dolphins
have had enough and they move on.

It looks as if they have picked
the sand clean...

...but here, at least,

there really are
plenty more fish in the sea.

Closer to the land,
the same tides bring nourishment

to one of the most threatened
of coastal habitats...

...mangrove forests...

...part land...

...part sea.

Mangroves are the only trees

capable of surviving in salt water

and are specially adapted to it
coming and going twice every day.

As seawater floods in, fish come with it.

Here, in the flooded forests,

they can find both food and shelter.

Stingrays ride on the incoming tide.

Other commuters follow.

Young lemon sharks,
still far from full-grown,

are looking for food.

When the tide is at its highest,

even adult lemon sharks

can get into the mangroves.

A three-metre female
moves cautiously into the shallows.

She can't stay here for long,

but then she hasn't come here to hunt.

She's come to give birth...

...returning to the very place
where she was born.

She has nourished the pups
inside her body with a placenta,

as we do.

The mangroves provide
an ideal nursery for them,

and placing them here gives them
an excellent start,

but that is the end of her parental care.

She has to return to deeper water

before the tide goes out.

Her young must now fend for themselves.

The pups instinctively take refuge
among the roots of the mangroves.

They're so small they can swim deep
into this tangled labyrinth.

With the tide fast receding,

even they need to find a place

where they won't be left high and dry...

...a place like this...

...a permanent pool
in the heart of the mangrove forest.

Only the smallest sharks can get here,

and only at the highest tides.

The pups will spend
the next two years here,

perfecting the skills that make them
one of the ocean's top hunters.

And it seems...

...that there's a lot to learn.

Got one!

All life at the coasts has to move
to the daily rhythm of the tides,

but tides are not the same
throughout the year.

Every month, when our planet,
the moon and the sun are all aligned,

the increased gravitational pull
produces particularly high tides.

And this triggers
a truly extraordinary event

on one particular reef
in the central Pacific.

Thousands of resident surgeon fish

begin to assemble on these high tides.

And they are being followed
by one of the largest fish in the sea...

...manta rays.

The rays spend their year
moving between coral islands.

But it's only now,
when the tide is at its highest

and the surgeon fish have gathered,

that they appear on this particular reef.

Their timing is so perfect

that they rarely have to wait
more than an hour

for the event to begin.

At the precise moment
when the tide is at its highest,

the surgeon fish begin to spawn.

They release billions of eggs and sperm
into the water.

Breeding in this way
gives their fertilised eggs

the best chance
of being carried on the tide

away from predators that haunt the reef...

...all except one.

The mantas move in.

They gorge on the eggs,

filtering them out
using specially adapted gills.

If the mantas had arrived
just an hour later,

there would have been nothing here
for them to eat.

No-one knows how the mantas
are so perfectly in tune

with the rhythm of the tides.

But they appear without fail
whenever the surgeon fish spawn.

Most of the eggs, however,

are carried out into the open ocean

before the mantas
are able to eat them all.

The rhythms of coastal life
are influenced by another ocean force.

Winds blowing over the sea
so batter the surface

that it begins to rise and fall.

These swells may travel far

and reach the shores
of even the most sheltered bays.

As they approach shallower water,

they turn into waves.

A shoal of hardyheads,

close to the beach
of Australia's Lizard Island.

The clearness of these glassy waters
shows that they lack nutrients.

But the gentle waves
expose food hidden in the sand,

and that's what
the hardyheads are looking for.

But...they must beware.

Packs of trevally are on the hunt.

The hardyheads stick together.

There's safety in numbers.

But they're vulnerable nonetheless.

They're so small,
they can swim in the shallowest waters...

...even in the body
of the waves themselves,

out of the reach of their enemies.

But trevally aren't their only concern.

Blacktip reef sharks.

They are bigger and more powerful
than trevally...

...but not as fast or as agile.

The hardyheads are well aware of them,

but so long as they stay just
out of reach, they have little to fear.

But now the sharks and the trevally
join forces.

Together, they enter the shallows,

each looking for a chance to attack.

The trevally make the first move...

...and the hardyheads take refuge again
in the waves.

And this is what
the sharks have been waiting for.

Surging forwards, they chase
the hardyheads out of the water...

...beaching themselves
in a daring bid to hoover up their prey.

The hardyheads that escape the sharks

swim back out to deeper water...

...but into the mouths of the trevally.

Now the receding waves
help to pull the sharks back

into deeper water.

In the chaos,
the seabirds get their chance.

It's a feeding frenzy

in only ten centimetres of water.

The power of waves
is dramatically evident

when they crash onto our shores.

But the biggest of all
start far away from land, out at sea.

(THUNDER CRASH ES)

Great storms blowing over
the surface of the ocean

raise towering walls of water.

Such giant swells
can travel for thousands of miles.

As they approach land,

the shallowing sea floor begins
to drag on their undersides,

and they topple forward...

...and break.

This stirring of the ocean
produces great riches.

The Falkland Islands are surrounded by
some of the stormiest waters on Earth...

...ideal hunting grounds
for rock hopper penguins.

It's the breeding season,

and for the last two weeks, the males have
been incubating the eggs by themselves.

They're confined to the nest
with nothing to eat,

while the females are out at sea
collecting food.

All across the colony,
eggs are starting to hatch.

This male now has two youngsters
to care for.

But he has no food to give them,
and he can't leave them unprotected.

He can do nothing but wait.

The females,
after weeks fishing in the stormy seas,

are now heading for home
with food in their crops.

There's just one problem.

The colony sits at the top of huge cliffs.

The waves that make feeding so good here

have now become major obstacles.

Timing is vital.

Go too early...

...and they could be smashed
against the rocks.

Too late...

...and they will be carried
back out to sea.

Hooked claws now help to get purchase

on the slippery rocks.

But they're not out of trouble yet.

Success depends on both judgment...

...and luck.

Time and again,
the waves drag her back in.

She has to persevere.

The lives of her chicks
depend on her safe return.

Finally...

...she's made it.

They're not called rockhoppers
for nothing.

With one more jump, she's home.

And just in time.

Her chicks are desperately hungry.

This is their first proper meal.

(CHICK CHEEPS)

The oceans have sustained life
on our planet for millions of years.

But today, there's growing evidence
that this is changing.

As our climate warms,

polar ice sheets are melting
at an alarming rate.

In the Arctic alone,
14,000 tonnes of fresh water

are emptying into the sea every second.

This is slowing the flow of currents
around the globe.

And if the atmosphere
continues to warm,

ocean circulation
could eventually stop altogether.

Our seas would then stagnate,

threatening the life within them.

And there are places in the oceans today

where this is already beginning to happen.

The Gulf of Thailand.

Eden's whales
have lived here for generations.

But the world around them is changing.

Today, agricultural pollution
flowing from the land...

...is beginning to suffocate this sea.

Many fish now stay closer to the surface,

where the waters still contain
enough oxygen to survive.

Eden's whales depend on these fish.

They swallow huge quantities of water

before filtering out their prey.

It takes a lot of energy to drive
their 15-tonne bulk through the water.

And with so few fish,

the rewards from feeding like this
are barely worth it.

So, to survive here,

the whales have developed
a new hunting technique...

...one that requires almost no effort.

They simply open their mouths...

...and wait.

The panicked fish jump right in.

Swimming alongside,

another whale scares even more
into the open jaws.

With this ingenious new technique,

Eden's whales have found a way
to survive the pressures they now face.

All across the planet,

animals are having to adapt

to a changing world.

But the speed of these changes

will be too fast for many.

If we could only halt
our unrestrained plunder of the ocean,

its habitats and species would recover.

And at a time when our overexploited lands
are already failing us,

this has never been more important
for humanity.