All language subtitles for BBC.Natures.Microworlds.04of13.Monterey.Bay.720p.HDTV.x264.AAC.MVGroup.org Eng

Our Planet is the greatest living
puzzle in the Universe.

A collection of worlds
within worlds.

Each one a self-contained
ecosystem, bursting with life.

But how do they work?

The intricate web of relationships
and the influence of natural forces,

makes each microworld
complex and unique.

So to discover their secrets,
we need to explore them one by one.

Untangle their interlocking pieces

and ultimately reveal the vital
piece, the key to life itself,

hidden deep within
each of nature's microworlds.

At the centre of
California's sunshine coast

are the waters of Monterey Bay.

America's largest marine sanctuary

and one of the most diverse marine
ecosystems on the planet.

Below the waves is
an explosion of life.

From the mammoth,

to the microscopic.

All living in
and around a giant kelp forest

that is home to over 300 species of
fish and thousands of invertebrates.

And that's just below the water.

With such abundance of life,
the key to success is balance.

But what maintains this balance?

Each species finding its niche,
none out weighing the other.

This is no mean feat,

it's a complex
web that could be easily upset.

But Monterey has a secret weapon.

Scientists discovered that a single
species holds the key

to the balance of life
in the entire bay.

To find out what this species is,

let's journey through this
remarkable place,

and take a closer
look at its key characters.

And what better place to start than
with the most impressive.

It might not
look like much from above,

but below the surface of the bay
is a forest,

as lush and vibrant as any on land.

Spires of kelp, as tall as houses,

grow from the sea floor
to the surface,

up to 30 meters above,
forming a dense canopy.

Like a rainforest,
the kelp makes a home

for a myriad of incredible
creatures,

bizarre sea hares,

flashy Garibaldis

and fierce wolf eels,

each one more colourful,
weird or wonderful than the next.

So much diversity in fact, that
as many as 100,000 creatures

can be living on a square
meter of kelp at any time.

Although playing the role of tree
in this underwater forest,

kelp is not actually a plant
but a giant or macro algae.

These impressive spires can grow up
to a metre a day

under the right conditions.

They rely on photosynthesis,

using sunlight to convert gases
and nutrients

into the material
needed for this astonishing growth.

Holdfast fingers cling to the rocky
floor, anchoring the kelp.

While floats filled with air keep it
growing toward the sun.

Chlorophyll in the blades absorb
the sun's energy,

just like in the leaves of plants.

But this is where the
similarity ends.

Kelp has no vascular system,

no roots forging into the earth or
internal structures to suck up

water and nutrients and transport
them from the root to its cells.

Kelp works in a very unusual way.

The blades directly absorb water and
nutrients from their surroundings.

All types of kelp and seaweed
photosynthesise in this way.

But the kelp on this stretch
of California's coastline

grows extraordinarily thick
and fast,

which is why it can support
such rich marine life.

And the reason it does
so well here

is down to
the geography of the bay itself.

Monterey sits on a gently
sloping shelf,

the edge of the American continent.

Where it meets the ocean,

the shelf suddenly gives way to
something more dramatic.

A rift deeper than the Grand Canyon

plummeting 5 kilometres down to
the ocean floor.

No light can penetrate to its
depths, an altogether different

microworld, dark, mysterious
and removed from the world above.

But surprisingly it is this canyon

that holds the key to
the kelp's success.

The canyon floor is thick with
decaying matter, the remains of life

from the water column above that
have sunk and slowly decomposed.

Now we see why Monterey is
so unique.

Normally this nutrient soup
would settle.

Instead, strong offshore winds push
surface water away,

forcing this deep water to rise
and take its place.

And these upwellings
deliver a constant stream

of nutrient-rich water to the bay.

The kelp forest has all
the ingredients needed

for successful photosynthesis
and gargantuan growth.

The forest makes the perfect
habitat.

Attracting an incredible
number of species.

All interacting,
competing for food and space.

Kelp provides the stage for
diversity

but it doesn't keep the balance.

If anything, it's what makes life
here so complex in the first place.

The species we are looking for

must somehow keep
this busy forest in check.

Just like a terrestrial forest,

the spires support life at different
levels, from the ground up.

The holdfasts that anchor the kelp
to the seabed provide cover

for spiny brittle stars,

shy pygmy octopus,

and the bizarre decorator crab,

a master of disguise, pain-stakingly
attaching bits of kelp

on to his shell until
he blends in with his surroundings.

Tiny amphipods
make their home in the lower blades.

Not only do they eat the kelp
but they also use it as protection.

Like spiders, they produce silk,

weaving together two edges
of the blade to make a safe space,

a hideout from predators,
protecting her and her young.

A few storeys up the flamboyant
Spanish dancer, a sea slug,

flaps from one blade to the next.

While young fish use the higher
blades as a safe nursery

before heading out to deeper waters.

The most bizarre fish is using
the top reaches of the kelp.

This is the Mola Mola, or sun fish.

Unusual doesn't quite cover it.

Not only do they look like a science
experiment gone wrong

but they can grow to gigantic sizes.

From a tiny egg, Molas can increase
in size up to 60 million times

to the weight of a large car.

It's an open sea fish that
has come inshore

because of an uncomfortable problem.

A parasitic infestation that it
can't tackle on its own.

By swimming at the surface
of the kelp it can enlist the help

of the half moon fish that
find shelter there.

They'll happily pick off as many
parasites as they can find.

And for the parasites
that are tougher to shift,

the Mola Mola calls in some
heavy duty help.

By floating flat on the surface,
it advertises its problem

to a nearby gull,
who is more than happy to oblige.

All these animals might seem benign
and balanced within their habitat,

but with so many species
living on top of each other,

life in the kelp is not
always peaceful.

Most live under continual
threat of being consumed.

This sea fern provides
a disguise for the skeleton shrimp,

swiping at passing plankton.

While also being nibbled by
Polycera, a small sea slug.

Polycera leaves behind a slimy
trail as it moves around the kelp,

a line of bread crumbs for the large
predatory Navanax,

who uses chemoreceptors to
track it down.

What looks like moss or lichen,
is actually a tiny animal.

Bryozoa colonize the kelp blades,

filtering water for microscopic
bits of plankton.

They hide from predators
in tough shells

that have a similar composition to
those of crabs.

But the Garibaldi fish's mouth
parts are tough enough

to rip the Bryozoa from the kelp,
shell and all.

This fish's spectacular
colouring is a statement,

space is at a premium here,
it warns others off his patch.

The giant kelpfish
prefers to blend in.

Imitating the kelp in both looks
and movement

might just save him from a
hungry seal.

Although these interactions keep
the food chain going,

individually, they don't have
enough impact

to affect the balance of life.

Larger species might have
more bearing.

There's a giant hiding
out in the kelp.

The grey whale is not a year
round inhabitant,

but it's a pretty impressive
visitor.

It's made the 7,500 kilometre
journey from the freezing Arctic

to give birth in the warmer
waters of Southern California.

This is the longest migration of
any mammal on the planet.

Now the calf is strong enough,
they must make their way back

to Arctic feeding grounds, taking
them past the mouth of Monterey Bay.

But with a baby in tow, not only
does this journey become slower,

but far more dangerous.

They're not the only large
predators out here.

The grey whale mother has
a decision to make.

It can hug the coast, hiding
out in the cover of the kelp forest,

or cut straight
across the mouth of the bay.

This is the quicker route
but leaves her and her baby

out in the open
and vulnerable to attack.

A pack of deadly predators stalk
these waters,

Orcinus orca,
the aptly named killer whale.

Capable of 50 kilometre per hour
bursts, the potent predators

have no trouble catching up with
the slow moving pair.

But the power of the mother is not
to be underestimated.

Under attack,
grey whales react violently,

earning them the name devilfish
by early hunters.

The killers must play
to their strengths.

by giving chase
they hope to tire the calf.

This game of cat and mouse
can last hours

before the mother is forced to stop
for her exhausted calf.

Now the pack combine strength,

forcing themselves between the
whales and driving them apart.

Once the calf is separated,
it's all over.

The killer pack has won

and the mother must go on alone.

Battles between these large animals
might not have a direct effect

on the balance of life
in the lower reaches of the forest,

but they are still vitally
connected to the kelp.

What's left of the body of the baby
whale will sink to the sea floor,

break down and then be recycled back
to the surface by upwellings,

feeding the kelp
and supporting its tenants.

Perhaps the greatest impact that
large predators

have on life in the kelp,
is by indirectly contributing to

the nutrient cycle that helps
to sustain it.

The problem is that
with healthy kelp

comes the animals that want
to eat it.

These aren't just any grazers.

If we are looking for a species that
has a real impact on the kelp,

well, we've found it.

A herd of Sea urchins, kelp eaters.

They reproduce fast, doubling
their numbers in a matter of days

and they're armoured in spines that
few predators can break through.

This is an army built for a purpose.

Unlike other grazers,

urchins aren't only interested in
the kelp's blades.

Five sets of brutal, self-sharpening
calcium carbonate teeth

hit the kelp where it hurts most.

The holdfast may be tough enough to
withstand winter storms,

but it is no
match for the urchin's jaws.

These are capable of chomping
through rock.

By feeding at the base, sea urchins
can cut entire spires loose

and are capable of destroying whole
beds of kelp at a time.

Yet despite this onslaught,
the kelp proliferates.

Not because,
even with nutrient-rich waters,

it can outgrow urchin grazing,

but because it also supports
another species,

a creature equally ravenous.

Floating at the surface, lies the
secret to the success of the Bay.

A raft of sea otters have rolled
themselves in the kelp's fronds,

anchoring themselves in place

so they don't drift out to sea
while they sleep.

This may be the smallest sea mammal,

but with a voracious appetite
and a partiality for urchin meat,

it's crucially important to
the kelp forest.

With an adult typically eating up
to 30% of its body weight a day,

that could be 50 of the spiny
invaders,

the otter is Monterey Bay's secret
weapon of mass urchin destruction.

Although the urchins are typically
found on the sea floor,

otters make light
work of finding them.

Holding their breath for
five minutes,

they will dive up to 18 metres,

prizing urchins off the rocky
sea bed.

Sea otters aren't just
effective hunters,

they're also brilliant tool users,
cracking open their prey's shell

by banging it against a flat
stone on their stomach,

a clever way of getting past those
sharp spines,

munching on its
protein-rich innards.

Mothers pass on hunting
techniques to their pups,

although they can take a
while to perfect.

So many species rely on the kelp,
and therefore the otters' appetite,

which keeps the urchins in check.

But the question remains,

why do the otters need to eat
quite so much?

Unlike their neighbours,
the harbour seals and sea lions,

otters don't have
a thick blubber layer,

which is the usual defence
against cold water.

This means that their body heat is
constantly being lost

to the water around them.

Otters combat this in two ways.

Firstly with their fur, the densest
fur of any animal on the planet.

Up to a million hairs in an area
the size of a postage stamp,

trapping air, keeping the cool water
at bay and providing insulation.

Their loosely jointed skeleton means
they are flexible enough

to fluff air back even into those
tough to reach places.

In fact, this system works
so well that with careful grooming,

cold water never reaches
the skin at all.

This remarkable fur goes a long way
to keeping them warm,

but to keep their core internal
temperature up

they must constantly burn energy

and that means consuming calories,

lots of them.

Urchin control,
crucial as it is to the kelp,

is really just a side
effect of otter thermo-regulation.

Although populations of sea
otters are relatively small,

they are critical to
the balance of the ecosystem.

So they are what is
known as a keystone species,

guardians of the kelp forest.

The importance of sea otters to
the balance of the ecosystem

hasn't always been known.

Sadly it was learnt the hard way.

When settlers first
arrived on California's coast

they treated
the ocean like an open larder.

Few species were safe,
and the otter fared worst of all.

It's a sad irony that the beautiful
adaptation that made them

so suited to life in the bay put sea
otters at the brink of extinction.

Otters were hunted so heavily for
their pelts that within 100 years

they had vanished
from California's coastline.

For scientists it was a living
demonstration

of the key role that otters play.

With the keystone species removed,
urchin numbers rocketed,

devouring the kelp.

In several areas
along the Californian coastline

the forests disappeared altogether.

Once sea urchins have cleared
an area of kelp,

enough numbers will
remain in this barren area

to nip any regrowth in the bud.

These urchin barrens were
an ecological disaster.

Coastal fish and invertebrate
populations in Monterey plummeted

and so large predators
were forced to move away.

Although otter hunting was
officially banned in 1911,

it was too late.

No otters had been seen in the area
in living memory,

considered extinct...

Monterey Bay had lost its key.

Until a chance glance
down a telescope in 1938

turned the fates for this failing
ecosystem.

A secret community,
up to 300 animals strong,

living in a remote bay.

No-one knows how this fortunate
community survived

but their discovery heralded a new
dawn for Monterey Bay.

Scientists had seen what
happened to the ecosystem

when the keystone species
was removed.

Now they had the unique opportunity
to watch the effects of its return.

With hunting banned,
this otter population grew,

getting down to some serious
urchin eating.

Which gave kelp beds a chance to
take hold and grow.

With such a ready supply of food,

the secret population of hundreds
became thousands

and showed that where the
otter went, healthy kelp followed.

Monterey's keystone species
was recovering,

allowing the ecosystem to
recover with it,

link by link.

Today, Monterey Bay is once again

one of the most diverse marine
habitats on earth.

It's a real ecological
success story.

We have seen just how complex
the web of life is here

and how quickly it can fall apart.

So it's crucially important that
the bay is protected.

And with its otter guardians
in place,

keeping urchin grazers
under control,

the future looks bright for
Monterey.

The balance has returned.

The kelp forest and its tenants
are thriving.

The hope is,

that by protecting these waters and
its keystone species,

this diverse marine ecosystem will
continue to be spectacular.