Original subtitles

David Attenborough: Dwarfed by the vast expanse

of the open ocean,

the biggest animal that has ever lived on our planet.

A blue whale, 30 meters long and weighing over 200 tons.

It's far bigger than even the biggest dinosaur.

Its tongue weighs as much as an elephant.

Its heart is the size of a car,

and some of its blood vessels are so wide

that you could swim down them.

Its tail alone is the width of a small aircraft's wings.

Its streamlining, close to perfection,

enables it to cruise at 20 knots.

It's one of the fastest animals in the sea.

The ocean's largest inhabitant

feeds almost exclusively on one of the smallest--

krill, a crustacean just a few centimeters long.

Gathered in a shoal,

krill stain the sea red,

and a single blue whale in a day can consume 40 million of them.

Despite the enormous size of blue whales,

we know very little about them.

Their migration routes are still a mystery,

and we have absolutely no idea where they go to breed.

They are a dramatic reminder

of how much we still have to learn about the ocean

and the creatures that live there.

Our planet is a blue planet.

Over 70% of it is covered by the sea.

The Pacific Ocean alone covers half the globe.

You can fly across it nonstop for 12 hours

and still see nothing more than a speck of land.

This series will reveal

the complete natural history of our ocean planet

from its familiar shores

to the mysteries of its deepest seas.

By volume,

the ocean makes up 97%

of the Earth's inhabitable space,

and the sheer quantity of marine life it contains

far exceeds that which inhabits the land.

But life in the ocean is not evenly spread.

It's regulated

by the path of currents carrying nutrients,

and the varying power of the sun.

In this first program, we will see

how these two forces interact

to control the distribution of life

from the coral seas to the polar wastes.

The sheer physical power of the ocean

dominates our planet.

It profoundly influences the weather of all the world.

Water vapor rising from it forms the clouds

and generates the storms

that ultimately will drench the land.

Can you feel it?

You're exactly where you're meant to be right now.

You and me, we could do anything.

Us against the world.

Welcome to the Theatre des Vampires.

You have no idea what I'm capable of.

My word means something.

We need you...

...to lead the revival of humanity.

You deserve a happy ending.

Well, guess this is it, then.

The great waves that roar in towards the shores

are dramatic demonstrations of its power.

Waves originate far out at sea.

There, even gentle breezes can cause ripples,

and ripples grow into swells.

Out in the open ocean, unimpeded by land,

such swells can become gigantic.

It's only when an ocean swell eventually reaches shallow water

that it starts to break.

As it approaches the coast,

the water at the bottom of the swell

is slowed by contact with the seabed.

The top of the swell, still traveling fast,

starts to roll over,

and so the wave breaks.

The ocean never rests.

Huge currents, such as the Gulf Stream,

keep its waters constantly on the move all 'round the globe.

It's these currents, more than any other factor,

that control the distribution of nutrients

and life in the seas.

A tiny island lost in the midst of the Pacific.

It's the tip of a huge mountain

that rises precipitously from the sea floor

thousands of meters below.

The nearest land is 300 miles away.

Isolated seamounts like this one

create oases where life can flourish

in the comparatively empty expanses of the open ocean.

But all the creatures that swim beside it would not be here

were it not for one key factor--

the deep ocean currents.

Far below the surface, they collide with the island's flanks

and are deflected upwards,

bringing with them from the depths

a rich soup of nutrients.

Such upwellings attract great concentrations of life.

Most of the fish here are permanent residents

feeding on the plankton--

the tiny floating plants and animals

that are nourished by the richness

brought up from the depths--

and they in turn attract visitors from the open ocean.

Tuna.

The plankton feeders are easy targets.

All this action attracts even larger predators.

Sharks.

Hundreds of sharks.

These silky sharks are normally ocean-going species,

but the seamounts in the Eastern Pacific,

like Cocos, Malpelo, and the Galapagos,

attract silkies in huge groups

up to 500 strong.

Silkies seem to specialize in taking injured fish

and constantly circle seamounts

on the lookout for the chance to do so.

But silkies are not the only visitors.

Hammerheads gather in some of the largest shark shoals

to be found anywhere in the ocean.

Sometimes, thousands will circle over a single seamount.

But these sharks are not here for food.

They have come for another reason.

Some of the locals provide a cleaning service.

Following the last El Niño year,

when a rise in water temperatures

caused many sharks to suffer from fungal infections,

the number of hammerheads visiting the seamounts

reached record levels.

Nutrients also well up to the surface

along the coasts of the continents.

This is Natal on South Africa's Eastern seaboard.

It's June, and just offshore,

strange black patches have appeared.

They look like immense oil slicks up to a mile long.

But this is a living slick--

millions and millions

of sardines on a marine migration

that, in terms of sheer biomass,

rivals that of the wildebeest on the grasslands of Africa.

These fish live for most of the time

in the cold waters south of the cape,

but each year, the coastal currents reverse.

The warm Agulhas current

that usually flows down from the north

has been displaced by cold water coming up from the south,

and that has brought up rich nutrients.

They in turn have created a bloom of plankton,

and the sardines are now feasting on it.

As the sardines travel north,

a whole caravan of predators follow them.

Thousands of Cape gannets track the sardines.

They nested off the Cape and timed their breeding

so that their newly fledged chicks can join them

in pursuing the shoals.

Below water, hundreds of sharks have also joined the caravan.

These are bronze whaler sharks,

a cold-water species that normally lives

much further south.

These three-meter sharks

cut such great swathes through the sardine shoals

that their tracks are clearly visible from the air.

Harried by packs of predators

and swept in by the action of the waves,

the sardine shoals are penned close to the shore.

Common dolphin are coming in from the open ocean

to join the feast.

There are over a thousand of them

in this one school.

When they catch up with the sardines,

the action really begins.

Working together, they drive the shoal towards the surface.

It's easier for the dolphins to snatch fish up here.

Now the sardines have no escape.

Thanks to the dolphins,

the sardines have come within the diving range of the gannets.

Hundreds of white arrows shoot into the sea,

leaving long trails of bubbles behind each dive.

Next to join the frenzy are the sharks.

Sharks get very excited when dolphins are around.

That may be because they can feed particularly well

once the dolphins have driven the sardines

into more compact groups near the surface.

As the frenzy continues,

walls of bubbles drift upwards.

They are being released by the dolphins,

working together in teams.

They use the bubbles

to corral the sardines into ever tighter groups.

The sardines seldom cross the wall of bubbles

and crowd closer together.

Bubble netting in this way

enables the dolphins to grab every last trapped sardine.

Just when the feasting seems to be almost over,

a Bryde's whale.

The survivors head on northwards,

and the caravan of predators follows them.

Nutrients can also be brought up,

though less predictably, by rough weather.

Particularly near the Poles,

huge storms stir the depths

and enrich the surface waters.

And here in the South Atlantic,

the seas are the roughest on the planet.

And very rich seas they are, too,

for here, the cold Falklands Current from the south

meets the warm Brazil Current from the north,

and at their junction, there is food in abundance.

These black-browed albatross are duck diving for krill

that has been driven up to the surface.

Like all albatross, black-brows are wanderers

across the face of the open ocean.

A feeding assembly on this scale is a rare sight.

Most of the time, the birds of the open sea

are widely dispersed.

But these feeding grounds are close to

an albatross breeding colony, and a very special one.

This is Steeple Jason,

a remote island in the far west of the Falklands.

It has the largest albatross colony in the world.

There are almost half a million albatross here,

an astonishing demonstration of how fertile the ocean can be

and how much food it can give

even to creatures that do not actually live in it.

Nutrients by themselves are not enough

to generate these vast assemblies.

The heat and light that the sun brings every day

is also essential for the growth

of the microscopic floating plants, the phytoplankton.

And it's the phytoplankton

that is the basis of all life in the ocean.

Every evening,

the disappearance of the sun below the horizon

triggers the largest migration of life

that takes place on our planet.

One thousand million tons of sea creatures

ascend from the deep ocean

to search for food near the surface.

They graze on the phytoplankton under cover of darkness.

Even so, they are far from safe.

Other marine hunters follow them,

some traveling up from hundreds of meters below.

At dawn, the whole procession returns

to the safety of the dark depths.

The moon, too, has a great influence on life in the oceans.

Its gravitational pull creates

the daily advances and retreats of the tide.

But the moon has more than a daily cycle.

Each month, it waxes and wanes as it travels round the Earth.

And this monthly cycle also triggers events in the ocean.

The Pacific coast of Costa Rica

on a very special night.

It's just after midnight, and the tide is coming in.

The moon is in its last quarter,

exactly halfway between full and new.

For weeks, the beach has been empty,

but that is about to change.

At high tide, turtles start to emerge from the surf.

At first, they come in ones and twos,

but within an hour,

they are appearing all along the beach.

They are all female ridley's turtles,

and over the next six days or so,

400,000 will visit this one beach

to lay their eggs in the sand.

At the peak time, 5,000 are coming and going every hour.

The top of the beach gets so crowded

that they have to clamber over one another

to find a bare patch

where they can dig a nest hole.

A quarter of the world's population of ridley's turtles

come to this one beach on a few key nights each year.

The rest of the time,

they are widely distributed through the ocean,

searching for food,

most, hundreds of miles away from here.

This mass nesting is called an arribada.

How it's coordinated is a mystery,

but we do know that arribadas start

when the moon is either in its first or its last quarter.

Forty million eggs are laid in just a few days.

By synchronizing their nesting in this way, the females ensure

that six weeks later, their hatchlings will emerge

in such enormous numbers that predators on the beach

are overwhelmed,

and a significant proportion of the baby turtles

will get past them and make it to the water.

But why do the females use a cue from the moon

to help in synchronize their nesting?

Part of the answer to that

becomes clear at dawn on the following morning.

The day shift of predators

are arriving for their first meals.

Vultures have learnt that the returning tide

can wash freshly laid eggs out of the sand.

The risk of eggs' being exposed by the surf

may be part of the reason why turtle arribadas tend to occur

around the last or first quarter of the moon.

It's on such days as this,

when the moon is neither full nor new,

that the tides are weakest

and the sea is likely to be calmer.

So at these times it's easier for the female turtles

to make their way through the surf,

and there's less chance of their eggs' being washed

out of the sand and being taken by the vultures.

The moon's monthly cycle

and its influence on the tides

triggers many events in the ocean,

from the spawning of the corals on the Great Barrier Reef

to the breeding cycles of fish.

But there's an even longer rhythm

that has the most profound effect of all--

the annual cycle of the sun.

The sun's position relative to the Earth

changes through the year,

and it's this that produces the seasons.

In the North, spring comes

as the sun begins to rise higher in the sky.

Off the coast of Northwest America,

the seas are transformed

by the increasing strength of the sunshine.

Here in Alaska, the coastal waters turn green

with a sudden bloom of phytoplankton.

Herring that have spent the winter far out to sea

time their return to the shallow waters

to coincide with this bloom.

They come in vast numbers and initiate

one of the most productive food chains in all the oceans.

Humpback whales are at the top of that food chain.

They have spent the winter

breeding in the warmer tropical waters off Hawaii,

but there was little food for them there.

This herring bonanza provides the vast majority

of their food for the year.

Stellar and Californian sea lions

also return from the open ocean

each year to feast off the herring.

The herring themselves, however, have not come here for food.

They are about to breed.

Nothing deters them

as they head for even shallower waters.

Now the waters are so shallow

that glaucous-winged gulls

are able to snatch live fish from just below the surface.

In spite of these attacks and losses,

the herring swim on until they reach the vegetation

that the females need if they are to lay.

Each female produces around 20,000 eggs,

and they're very sticky.

The males arrive soon after the females have spawned

and release their sperm in vast, milky clouds.

Soon, the excesses of the herrings' sexual spree

creates a thick white scum on the surface.

Through the season, curds of sperm clog the shores

for hundreds of miles

from British Columbia in the south

all the way to Alaska in the north.

After a few days, this gigantic spawning comes to an end,

and the herring head back out to deeper waters,

leaving behind them fertilized eggs

plastered on every rock and strand of vegetation.

They time their spawning

so that two weeks later, when these eggs start to hatch,

the annual plankton bloom

will have reached its height,

and the newborn fish fry will have plenty to eat.

But in the meantime, all these eggs provide food

for armies of different animals

both below and above the surface.

Millions of birds arrive

to collect a share of the herrings' bounty.

Some of it is easily gathered,

for millions of eggs have been washed up onto the shore.

This encapsulated energy

is particularly valuable to migrating birds.

These surfbirds are on their way

to their breeding grounds in the Arctic,

and they had to come down to refuel.

Stranded herring eggs are just what they need.

Bonaparte gulls collect the eggs

just below the surface of the water.

Farther out in the bay,

huge flocks of ducks have gathered.

They're mostly surf scoters--

diving ducks that can feed off the bottom

several meters down.

There are such huge quantities of eggs

that even such a big animal as a bear

finds it worthwhile to collect them.

The spawning of the herring is a crucial event

in the lives of many animals all along the coast.

The whole event coincides with the plankton bloom,

and within just three short weeks, it's all over.

The migratory birds leave to continue their journey north.

They will not come back

until the herring also return next year.

As the herring spawning finishes,

other migrants are starting to arrive just offshore.

Gray whales.

They have followed the sun north,

and they too are seeking the food

that is generated by the bloom of the phytoplankton.

Krill are feeding off it,

and these whales are feeding on the krill,

skimming it from the surface with the filter plates of baleen

that hang from their upper jaws.

Gray whales make one of the longest migrations

undertaken by any marine mammal--

a round trip of 12,000 miles or so

from their breeding grounds off Mexico

along the entire coast of North America

right up to the Arctic Ocean.

They travel close to the coast,

with the males and non-breeding females leading the way.

The last to start are the cows that have just given birth.

They have to wait until their newborn calves

are sufficiently big and strong

to tackle such an immense journey.

Their progress is necessarily slow.

The mothers must stay alongside their young,

and even a strong calf can only travel at a couple of knots.

They stick even closer to the shore,

often within just 200 meters.

Killer whales.

They have learnt that gray whales

follow traditional routes.

The killers have no trouble

in overtaking a calf and its devoted mother.

Normally, they continually call to one another,

but now they have fallen silent.

The mother gray whale and her calf

have no idea that they've been targeted.

Catching up with the gray whales

is the easy part for the killers.

They have to be cautious,

for they're only about half the size

of the gray whale mother.

She can inflict real damage with her tail.

But the killers are not after her.

They're after her calf.

As long as the mother can keep it on the move, it will be safe,

and she does her best to hurry it along.

At first, the killers avoid getting too close to the mother

but just keep pace alongside.

They know that the calf, going at this speed,

will eventually tire.

After three hours of being harried in this way,

the calf becomes too exhausted to swim any further.

The mother has to stop.

This is the moment the killers have been waiting for.

They start to try and force themselves

between mother and calf.

A calf separated from its mother

will not be able to defend itself.

Time and again, the black fins of the killers

appear between the mottled backs of the gray whales.

At last, the killers succeed,

and now that they've got the calf on its own,

they change their tactics.

They leap right onto the calf

and try to push it under.

They are trying to drown it.

The calf snatches a desperate breath.

The mother becomes increasingly agitated.

Frantically, she tries to push her calf back to the surface

so that it can breathe.

But now it's so exhausted

that it has to be supported by its mother's body.

The killers won't give up.

Like a pack of wolves, they take turns in harassing the whales.

Now the whole pod is involved.

One of them takes a bite.

Soon, the sea is reddened with the calf's blood,

and the killers close in for the final act.

The calf is dead.

After a six-hour hunt,

the killer whales have finally won their prize.

The mother, bereft,

has to continue her migration north on her own.

She leaves behind the carcass of a calf

that she cherished for 13 months in her womb,

for which she delayed her own journey to find food.

The pod of 15 killer whales

spent over six hours trying to kill this calf,

but now, having succeeded,

they've eaten nothing more than its lower jaw and its tongue.

Valuable food like this

will not go to waste in the ocean.

Before long, the carcass will sink

to the very bottom of this deep sea.

But even there, its flesh will not be wasted.

Over a mile down,

in the total darkness of the deep ocean,

the body of another gray whale, a 30-ton adult.

It settled here only a few weeks ago.

Already, it has attracted hundreds of hagfish.

These scavengers, over half a meter long

and as thick as your arm, are only found in the deep sea.

They have been attracted by the faint whiff of decay

suffusing through the water for miles around.

With their heads buried in the whale's flesh,

they breathe through gill openings

along the sides of their bodies.

They're very primitive creatures--

not even true fish, for they lack jaws.

They feed, not by biting,

but by rasping off flesh with two rows of horny teeth.

In just a few hours, a hagfish can eat

several times its own weight

of rotting flesh.

Next to arrive, a sleeper shark.

It moves so slowly to conserve energy--

an important strategy for so large an animal

surviving in such a poor habitat.

Sleeper sharks live over a mile down

and grow to over seven meters long.

They can go for months without food,

slowly cruising along the bottom,

waiting for rare bonanzas such as this one

to arrive from above.

A whole range of different deep-sea scavengers

will feast on this carcass for a long time

before all its nutriment has been consumed.

18 months later,

all that is left is a perfect skeleton stripped bare.

The sun's energy, that was captured

and turned into living tissue by the floating phytoplankton,

has been transferred from one link to another

in the food chain and has ended up

as far away from the sun

as it's possible to be on this planet--

at the bottom of the deep sea.

But some energy also returns from the deep.

Millions of opalescent squid

are on their way to the shallows.

They've come up here to mate.

As the males grab the females, their tentacles flush red.

For most of the year,

these squid live at a depth of around 500 meters.

They only come together

in these great breeding schools for a few weeks.

Just one school was estimated to contain animals

that weigh around 4,000 tons.

Wave after wave rise from the depths,

and soon the seabed in the shallows

is strewn with dense patches of egg capsules

several meters across.

As each female adds another capsule to the pile,

the males fight to fertilize its contents.

The squid make their huge journey into the shallows

because their eggs will develop faster in the warmer water here,

and when the young emerge,

they will find more food more easily

than they would in the ocean depths.

Dawn the next morning,

and the seabed for miles around is covered in egg capsules.

The squid themselves have all gone.

Many will have died,

but some will have returned to their home in the deep.

They will not return to the light of the sun

until the next time they are driven up by the urge to spawn.