All language subtitles for The Blue Planet (2001) - S01E07 - Tidal Seas (1080p BluRay x265 HEVC 10bit AAC 5.1 RCVR).en

There is a force sufficiently
powerful to move the oceans

of this world.

It is a force not of this Earth.

The Moon is large enough
to generate gravity

and with sufficient force to pull
on the Earth 230,000 miles away.

As the Moon orbits the Earth,

its gravity sweeps across
the face of our planet.

Its power drags a great bulge
of oceanic water in its wake...

...the rising tide.

The River Amazon in Brazil.

On some special days,
the gravitational forces

of the Moon and the sun combine,
to extraordinary effect.

A growing tidal wave from the ocean
is being forced 200 miles inland.

This is a tidal bore.

Fortunately, tidal bores are rare,

but the Moon does create strong tides
out in the world's oceans

on every day of the year.

The Bay of Fundy in Nova Scotia.

The tides here
are the largest in the world,

and have a profound effect
on marine life,

creating a rich feeding ground.

A feast that attracts some
of the largest diners on the planet...

...humpback Whales.

But they are not the biggest threat
to the hen-ing.

These are finback Whales.

At 70 tons, they are the second
largest animal on Earth,

but so streamlined they are
the fastest of the great whales.

This combination of speed
and immense size

makes the finback a voracious hunter
of schooling fish.

The Bay of Fundy
can attract so many fish

that, during the summer,

as many as 500 of these magnificent
whales hunt here every day.

The feeding is best
where the tides run strongly.

So the whales
move further into the bay,

following tidal lips
and searching for fish.

Their movements are closely watched
by flocks of Cary shearwaters.

As the whales dive down towards
the fish, more and more birds gather,

anxious to pick up scraps.

The flowing tide

may provide a feast,
but, before long, it will turn.

In just six hours,
100 billion tons of water

will flow out of the bay,

the sea level falling
by as much as 15 meters

and exposing vast tracts
of mud and sand.

At first sight, a barren place,
entirely devoid of life.

In fact, the damp sand
is packed with microscopic life,

the meiofauna,
feeding in a sandy underworld,

quite unaffected
by the departure of the sea.

But life is not all roses
in this miniature world.

A sand bubbler crab
in Northern Australia.

It hunts meiofauna.

Just a centimeter across,

the sand bubbler
works at breakneck speed,

filtering out the meiofauna
and kicking aside the waste.

The crab Will clean

every grain of sand
within a meter of its burrow.

Endless practice for the best
backheel in the natural world.

The crabs work fast

because they can only sieve
when the sand is damp.

Remarkably, they work
the entire surface of the beach

within a couple of hours
of the tide retreating.

Then they simply return to their
burrows and await the next tide.

Underwater,
the falling tide is the cue

for some bizarre activity.

These slow-moving clams
use their muscular feet

to bury themselves under the sand.

If they fail to get under cover,

the tide will leave them exposed
to the air and they will perish.

But once underground,
they can wait,

safe beneath the beach,

And not a moment too soon.

June in south east Alaska.

In just four hours, a vast beach
is exposed by the falling tide.

The bears are hungry.

At this time of year, the pickings
on land are few and far between.

But any food here has long since
buried itself deep under the sand.

To a hungry adult bear,
that is no barrier.

They smell the clams through
the sand and simply dig them out.

For such large animals,

they show
quite extraordinary dexterity

at opening
the unfortunate shellfish.

Cubs try their luck, too,
none too successfully.

But for the adults,
the shellfish feast

lasts as long
as the tide remains out.

Table Mountain in South Africa.

Every day, the retreating waves
leave flotsam on the beach.

And this creature
is scenting the currents

for the odor of rotting fish.

The tide carries the scent
far into the surf zone.

Responding to the smell,
snails emerge from the sand.

This is a race against the tide.

The snails need to find their meal

before the tide
leaves it beyond reach.

But snails are slow
and the tides fall rapidly.

These, however,
are no ordinary snails.

They can surf!

They ride the waves up the beach

but, all too soon, the tide leaves
the fish beyond the surf zone.

Without the sea, there 's a danger
the snails will lose the scent,

but as long
as the sand remains damp,

they can still follow
a faint trail to the food.

Once there,

they tuck in with macabre relish.

Good things come to those who wait.

Soon, the heat of the sun
forces them to retreat into the sand

to await the return
of the next tide.

February in Britain.

The falling tide is eagerly awaited
by these knot.

As the water retreats,
countless small invertebrates

seek shelter under the mud.

And with good reason.

Waders are specialists
at probing in the mud,

their variety of beak shapes

designed for reaching
different invertebrates -

keys that unlock the safety
of the tidal flats.

But Within a few hours,
the tide Will turn again.

Soon, the waders
are out of their depth.

The creatures of the mud
are safe once more.

Underwater, incoming tides
can create a strong current,

and flounder are experts
at hitching a tidal lift.

They are shaped
rather like a kite,

a perfect design
for gliding on the tide.

In Newfoundland
on the east coast of Canada,

large numbers of flounder ride
the currents up into the shallows.

They've come to hunt invertebrates

that will emerge
now that the water is back.

The pickings in the shallows
can be very good.

The activity
has not gone unnoticed.

But ospreys can't dive deeply.

As long as the water is more than
a meter deep, the flounder is safe.

Going too far inshore

can be a risky business.

This fish buries itself
completely in the sand

at any sign of danger.

But when the tide floods in again,
as long as the coast is clear,

these sand lancet Will re-emerge.

After a wait of six hours
under the sand,

they are desperate for food.

Unlike flounder,
they head out to sea,

looking for shallow, open water

where the tidal currents will
concentrate their food - plankton.

In untold thousands, they stream
towards the best feeding grounds,

Where they simply pick up

tiny planktonic creatures
from the water.

But, if they swim too far off-shore
in search of food,

they risk meeting large predators
that live in deeper water.

Dogfish - small sharks.

The sand lancet have strayed
out of their safe depth.

The effect of the turning tide

can be totally different
on a rocky shore.

Here, on the coast
of Vancouver Island in Canada,

the sun bakes the exposed rock.

It's almost impossible to dig
underground when the sea retreats,

so these mussels and barnacles
are fully exposed to the sun 's heat,

literally cooking
in their own shells.

And the seaweed
simply dry to a crisp.

It can be a wait of many hours
before the water returns.

Throughout each month, the size
and strength of the tide changes.

The biggest tides of all happen

when the gravities of the sun
and Moon pull in unison.

That happens immediately
after the new moon...

...and again after the full moon.

These are called the spring tides.

They reveal vast tracts of seabed
that would normally be covered.

For these raccoons, it's a chance
to look for a seafood feast.

A mother ventures forth
with her kits.

With the spring tide,
they've come further down

than smaller tides
would normally allow.

Searching
with their sensitive paws,

they look for suitable prey.

With the extreme low tide,
they could find something special.

And what could be better
than a red rock crab?

That is, if it weren't
for the risk of a painful pinch.

With crabs, there's no substitute
for experience.

The mother
makes an expert's catch.

But the kits learn fast.

And for those that don 't,
begging is always worth a try.

All too soon, the returning tide
will cover the raccoon '3 table.

For the invertebrates,
it's a welcome relief,

but in rough weather,
they are exposed

to the worst of the waves.

Even when there are no waves,

the incoming tide can create
considerable forces underwater.

The gaps between these islands
on the east coast of Vancouver Island

channel the tidal flow.

As the tide keeps rising,
gradually the water flows faster,

and soon these 30-meter-long
bull kelp plants

bend to the current.

They are sufficiently flexible
to cope without too much damage,

but there are some spots where
the currents are especially powerful.

This is the Nakwakto Rapids.

At the turn of the tide, water from
almost 700 miles of coastal fjords

will have to empty through a gap
half a mile wide.

Within a few minutes, the current
is already picking up speed,

until water roars by
at over 17 miles an hour.

Tidal currents
are not always damaging.

Here, in the Poor Knight Islands
of New Zealand,

weak tides run through rock arches,
making it an ideal resting place

for stingrays.

These rays congregate here
in huge numbers every March.

They've come to breed.

The arches funnel the current,
which the rays can ride

with the minimum of effort,
so saving energy.

Nearby, out in open water,

a school of two spotted demoiselle
fish are feeding on plankton,

and the current is perfect
for sweeping their food past them.

Once the current starts to weaken,

there is insufficient food

to warrant the risks
of swimming out in the open.

So, the demoiselles head off
to find shelter en masse.

Safety is in numbers.

More and more demoiselles
pour towards the cave entrances

that riddle the Poor Knight Islands.

Safe at last. Inside the cave,
they are less exposed

to attack from predators.

Thousands of demoiselles
and blue mao mao

wait for the return of the current,
when, once again,

they will head out
into the open to feed.

The Moon 's gravitational pull
is weaker

nearer to the Earth 's equator.

So, the more equatorial the location,
the smaller the tides.

Out in the Caribbean Sea,
the tidal movements are slight.

Even so, they are sufficient

to push free swimming plankton
in their path.

These are thimble jellyfish.

They swim towards sunlight,

and invisible boundaries
formed by the tidal motion

help to herd them together;
until they gather in immense swarms.

They put the tropical sunshine
to good use.

Their brown color comes from algae

that live inside
the jellyfish's body

and photosynthesize
energy from the sun.

In open water they are fairly safe,

but the tide is sweeping the Whole
swarm gently towards the Bahamas,

Where hungry mouths are waiting.

Although the sea level
doesn't change much,

the tides are still pushing
an enormous volume of ocean water

through the small gaps
between the island cays.

Underwater, the tidal currents
race past soft corals...

...and on over
the sandy banks themselves.

It is an immense area of coral sand

that is only just submerged
at high tide.

This incoming tide is bringing in
a fresh supply of oceanic plankton.

Razorfish gather at the best spots

to catch the pick
of the microscopic feast.

Although there 's plenty here
for these small fish to eat,

gathering in one place

makes it easy
for their predators to find them.

A nurse shark is little threat.

(CHIRPS AND CLICKS)
But this sound...

heralds a quite different danger.

A bottlenose dolphin.

It's using its sonar
to locate razorflsh beneath the sand.

Once it finds a suitable target,
it simply digs out its prey.

The buried fish have no defense
against this attack.

They simply have to wait
and hope they aren't found out.

This dolphin appears to have
a razorfish craving.

Well, she is pregnant.

Success at last.

The incoming tide
sweeps on towards America,

flooding across vast flat
plains of seagrass.

They are so shallow
that, at low tide,

all large fish are forced
to retreat into deep water channels,

like these nurse shark...

...and stingrays.

Both predators hunt crustaceans
on the seagrass beds,

but until the tide
brings enough water,

they will have to wait.

So now, for this tulip snail,
it appears safe

to patrol the shallows
in search of a meal.

But is it?

This is a rather bigger snail.

At five kilograms in weight,
the giant horse conch

has little to fear from any shark,
and it has a taste for tulip snail.

Sensing the approaching danger,

the snail flees.

But, in a world of snail paces,

the conch
is something of a Ferrari.

It calls for desperate measures.

Exhausted by the effort
of its last-ditch attempt,

the tulip snail
is slowly gunned down.

The tide has to rise
for another hour

before the big predators can feed.

But out on the flats, the scent of
dying snail wafts away on the tide.

It's a scent these hermit crabs
are particularly partial to.

It's vital that the crabs
have the best possible protection

from the heavy teeth
of the waiting sharks and rays.

For that, they need the shell
with the perfect fit.

Today, there is new real estate
on offer -

and competition
in this housing market is fierce.

The action becomes
even more desperate

when the shell of the devoured
snail is ready for release.

This crab simply can't wait
any longer.

But it's a decidedly risky
acquisition.

The risk paid off handsomely.

The new shell is both lighter
and stronger than the old home.

It's not a moment too soon,
because the tide is flooding the plains.

At last, the predators are free
to start their foraging.

Both stingrays and shark
have an electrical sense

which they use to search
for buried in vertebrates.

They can sense minute movements
beneath the sand.

Finding a promising signal,
this ray digs out its meal.

An unprotected hermit crab
would have no chance.

Within a few hours,
the tide ebbs out once more

and all the predators
are forced to leave.

They will have to wait
until the next high tide

before making
another feeding foray.

At certain times of the year,
called the equinox,

spring tides are exceptionally large
and rise higher than normal.

Predators can reach the shallowest
fringes of the seagrass flats.

These two-meter-long tarpon
are going further inshore still.

They are heading for the mangroves.

These flooded forests cover
huge areas of the coastal shallows.

Extraordinarily, the roots of
the mangrove can live in salt water,

and they make a perfect nursery
for small fish.

Silversides and snapper
find sanctuary in the maze of roots.

Big predators
seldom find a way in here.

And now the tide
is falling once more.

The water starts losing
what little oxygen it contained,

and quickly becomes stagnant.

Most predators
have abandoned the mangroves,

but the tarpon are still here,
trapped by the falling tide.

Dissolved oxygen
is fast running out,

but they have a vital survival
technique...

...they can breathe air.

Pumped up with fresh oxygen,

they can easily out-maneuver
the dozy silversides.

The tide has turned again.

And this is no ordinary tide.

Since it is the equinox,
the tide is rising fast,

but now, out to sea,

a hurricane is on its way,
forcing the tide yet higher.

The passing storm leaves large
areas of the coast flooded.

Low-lying islands,
like the Bahamas,

are particularly prone
to the storm flooding.

The sun '3 power here is immense.

As the tide recedes and the
remaining flood water evaporates,

a remarkable transformation
takes place.

The mud is coated
with a magical world of salt.

Any remaining water
is extremely salty.

Very few creatures
can survive here...

except brine shrimp.

And, on the water's edge -

brine flies.

Both are the favorite food
of an extraordinary animal.

The Caribbean flamingo.

Remarkably, they actually seek out
such briny places.

They are the best spots
for them to find their food.

They also provide the protection

the flamingos need
to raise their young.

Nesting sites like this
are surrounded by corrosive brine.

It's a formidable barrier

to any predator
seeking to dine on flamingo chicks.

The flamingos take the precaution
of building raised nests

just in case of further flooding.

Strangely, it's actually
the power of the storm tides

that gives the flamingos food and
a perfect habitat in which to breed.

The breeding of many animals
in the ocean

is closely coordinated
with the tidal cycles.

The half moon in November.
It's the time of small tides.

Christmas Island in the Pacific.

Strange happenings are afoot.

It's one of only
a few nights each year

when female Christmas Island crabs

risk heading down towards the sea.

They number in tens of thousands

and all of them are laden
with hundreds of eggs.

They have to shed them
into the ocean

if the eggs are to develop
into baby crabs.

But these are land crabs

and they can neither swim
nor breathe underwater.

There 's a great risk of drowning.

That is why they pick the smallest
tides, to minimize the danger.

The eggs Will develop far offshore.

And, in exactly one month '3 time,

a swarm of baby crabs will return,
again choosing the perfect tide.

Whether it's the daily
or monthly cycle,

tides are the rhythm of the ocean -

its pulsing clock.

For every tide brings opportunity

to marine life
somewhere in the world.

Now, a spring tide
is flooding the shallows,

and hunters are on the prowl.

A small group of bottlenose dolphin

are working their way inshore

to start a quite extraordinary
hunting campaign.

After one successful pass,
the dolphin move off to start again.

One animal peels off from the group
and swims in a circle,

stirring up the mud and driving
the mullet towards the other dolphins.

It's a remarkable team effort
and it's extremely effective.

The dolphin Will feed like this

for as long as the tide grants them
access to the shallows.

Eventually,

the falling tide will force
the dolphin to leave the flats

and the mullet will be safe
once more, until the next high tide.

Because, in the ocean,
every turn of the tide

spells the difference
between life and death somewhere.