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00:00Nuestro planeta es el más grande pússil viviendo en el universo.

00:05Un colección de mundos dentro de mundos.

00:09Cada uno un ecosistema de un ecosistema de vida.

00:13Pero cómo funcionan?

00:20El intercambio web de relaciones y la influencia de las fuerzas naturales

00:26hace cada micro-world complejo y único.

00:33Así que para descubrir sus secretos,

00:35tenemos que explorarlos uno por uno,

00:39untargar sus piezas interlocking,

00:42y finalmente revelar la pieza vitala,

00:46la clave a la vida itself,

00:49hidden deep within

00:51cada uno de los micró-worldos.

00:56At the center of California's Sunshine Coast

01:04are the waters of Monterey Bay,

01:08America's largest marine sanctuary

01:11and one of the most diverse marine ecosystems on the planet.

01:18Below the waves is an explosion of life.

01:21From the mammoth

01:28to the microscopic

01:30all living in and around

01:34a giant kelp forest

01:36that is home to over 300 species of fish

01:40and thousands of invertebrates.

01:45And that's just below the water.

01:49With such abundance of life,

01:52the key to success is balance.

01:54But what maintains this balance?

01:58Each species finding its niche,

02:00none outweighing the other.

02:05This is no mean feat.

02:08It's a complex web

02:09that could be easily upset.

02:14But Monterey has a secret weapon.

02:19Scientists discovered

02:20that a single species

02:21holds the key to the balance of life

02:23in the entire bay.

02:25To find out what this species is,

02:31let's journey through this remarkable place

02:33and take a closer look

02:34at its key characters.

02:36And what better place to start

02:44than with the most impressive?

02:48It might not look like much from above,

02:51but below the surface of the bay

02:54is a forest.

02:58As lush and vibrant

02:59as any on land.

03:01Spires of kelp

03:06as tall as houses

03:07grow from the seafloor

03:09to the surface.

03:12Up to 30 metres above.

03:15Forming a dense canopy.

03:21Like a rainforest,

03:23the kelp makes a home

03:24for a myriad of incredible creatures.

03:28Bizarre sea hares.

03:29Flashy garibaldies.

03:33And fierce wolf eels.

03:35Each one more colourful,

03:37weird or wonderful

03:38than the next.

03:41So much diversity, in fact,

03:43that as many as 100,000 creatures

03:46can be living on a square metre

03:47of kelp at any time.

03:55Although playing the role of tree

03:56in this underwater forest,

03:58kelp is not actually a plant

04:00but a giant

04:01or macro

04:02algae.

04:05These impressive spires

04:06can grow up to a metre a day

04:08under the right conditions.

04:11They rely on photosynthesis,

04:13using sunlight to convert

04:15gases and nutrients

04:17into the material needed

04:18for this astonishing growth.

04:20Hold fast fingers

04:25cling to the rocky floor,

04:27anchoring the kelp.

04:31While floats filled with air

04:33keep it growing

04:34toward the sun.

04:38Chlorophyll in the blades

04:39absorb the sun's energy,

04:42just like in the leaves of plants.

04:45But this is where

04:48the similarity ends.

04:52Kelp has no vascular system,

04:54no roots forging

04:56into the earth

04:56or internal structures

04:58to suck up water

04:59and nutrients

04:59and transport them

05:01from the root

05:01to its cells.

05:04Kelp works

05:05in a very unusual way.

05:07The blades directly absorb

05:10water and nutrients

05:12from their surroundings.

05:16All types of kelp

05:17and seaweed

05:18photosynthesize

05:20in this way.

05:21But the kelp

05:22on this stretch

05:23of California's coastline

05:24grows extraordinarily

05:25thick and fast.

05:29Which is why

05:30it can support

05:30such rich marine life.

05:34And the reason

05:35it does so well here

05:36is down to the geography

05:37of the bay itself.

05:44Monterey sits

05:45on a gently sloping shelf,

05:47the edge

05:47of the American continent.

05:51Where it meets the ocean,

05:53the shelf suddenly gives way

05:55to something more dramatic.

05:59A rift deeper

06:01than the Grand Canyon,

06:03plummeting five kilometers

06:04down to the ocean floor.

06:08No light can penetrate

06:09to its depths.

06:11An altogether different

06:12microworld.

06:14Dark, mysterious,

06:15and removed

06:16from the world above.

06:19But surprisingly,

06:20it's this canyon

06:21that holds the key

06:22to the kelp's success.

06:24The canyon floor is thick

06:28with decaying matter.

06:31The remains of life

06:32from the water column above

06:34that have sunk

06:35and slowly decomposed.

06:38Now we see

06:40why Monterey

06:40is so unique.

06:43Normally,

06:44this nutrient soup

06:45would settle.

06:46instead,

06:49strong offshore winds

06:51push surface water away,

06:54forcing this deep water

06:55to rise

06:55and take its place.

06:59And these upwellings

07:01deliver a constant stream

07:02of nutrient-rich water

07:03to the bay.

07:04The kelp forest

07:08has all the ingredients

07:10needed

07:10for successful photosynthesis

07:12and gargantuan growth.

07:19The forest

07:21makes the perfect habitat,

07:23attracting an incredible

07:26number of species,

07:27all interacting,

07:29competing for food

07:30and space.

07:31kelp provides

07:34the stage

07:35for diversity,

07:36but it doesn't

07:37keep the balance.

07:40If anything,

07:41it's what makes life here

07:42so complex

07:43in the first place.

07:46The species

07:47we're looking for

07:48must somehow

07:49keep this busy forest

07:50in check.

07:56Just like

07:57a terrestrial forest,

07:59the spires

08:00support life

08:00at different levels

08:02from the ground up.

08:08The holdfasts

08:09that anchor the kelp

08:10to the seabed

08:11provide cover

08:12for spiny brittle stars.

08:17Shy pygmy octopus

08:18and the bizarre

08:22decorator crab.

08:25A master of disguise,

08:28painstakingly attaching

08:29bits of kelp

08:30onto his shell

08:31until he blends in

08:32with his surroundings.

08:39Tiny amphipods

08:40make their home

08:40in the lower blades.

08:43Not only do they

08:44eat the kelp,

08:45but they also use it

08:46as protection.

08:47like spiders,

08:51they produce silk.

08:56Weaving together

08:57two edges of the blade

08:58to make a safe space.

09:02A hideout from predators

09:03protecting her

09:06and her young.

09:08A few stories up,

09:17the flamboyant

09:19Spanish dancer,

09:21a sea slug,

09:22flaps from one blade

09:23to the next.

09:28While young fish

09:29use the higher blades

09:31as a safe nursery

09:32before heading out

09:33to deeper waters.

09:34The most bizarre fish

09:39is using the top

09:40reaches of the kelp.

09:43This is the

09:44mola mola

09:45or sunfish.

09:48Unusual

09:48doesn't quite cover it.

09:51Not only do they

09:52look like a science

09:53experiment gone wrong,

09:55but they can grow

09:56to gigantic sizes.

09:58From a tiny egg,

10:02molars can increase

10:03in size

10:03up to 60 million times

10:06to the weight

10:08of a large car.

10:11It's an open sea fish

10:13that has come inshore

10:14because of an

10:15uncomfortable problem.

10:20A parasitic infestation

10:22that it can't tackle

10:23on its own.

10:24By swimming

10:28at the surface

10:28of the kelp,

10:29it can enlist

10:30the help

10:30of the half-moon fish

10:32that find shelter there.

10:35They'll happily

10:36pick off

10:37as many parasites

10:38as they can find.

10:41And for the parasites

10:43that are tougher

10:43to shift,

10:45the mola mola

10:46calls in

10:46some heavy-duty help.

10:51By floating

10:52flat on the surface,

10:53it advertises

10:54its problem

10:55to a nearby gull.

10:58Who's more than

10:59happy to oblige?

11:15All these animals

11:16might seem benign

11:18and balanced

11:18within their habitat.

11:19But with so many species

11:23living on top

11:23of each other,

11:25life in the kelp

11:27is not always peaceful.

11:30Most live under

11:31continual threat

11:32of being consumed.

11:34This sea fern

11:41provides a disguise

11:42for the skeleton

11:43shrimp,

11:46swiping

11:46at passing

11:47plankton,

11:48while also being

11:51nibbled

11:51by polysera,

11:53a small sea slug.

11:57Polysera

11:57leaves behind

11:58a slimy trail

11:59as it moves

11:59around the kelp.

12:00A line of breadcrumbs

12:03for the large

12:04predatory Navonax,

12:06who uses chemoreceptors

12:09to track it down.

12:18What looks like moss

12:20or lichen

12:20is actually

12:22a tiny animal.

12:23Bryozoa colonize

12:26the kelp blades,

12:31filtering water

12:34for microscopic

12:34bits of plankton.

12:39They hide from predators

12:40in tough shells

12:42that have a similar

12:43composition

12:43to those of crabs.

12:47But the Garibaldi

12:48fish's mouthparts

12:49are tough enough

12:50to rip the Bryozoa

12:51from the kelp,

12:52shell and all.

12:56This fish's

12:57spectacular colouring

12:59is a statement.

13:01Space is at a premium here.

13:04It warns others

13:05off his patch.

13:11The giant kelp fish

13:13prefers to blend in.

13:15Imitating the kelp

13:16in both looks

13:17and movement

13:18might just save him

13:20from a hungry seal.

13:25Although these interactions

13:26keep the food chain going,

13:29individually,

13:30they don't have enough impact

13:31to affect

13:32the balance of life.

13:36Larger species

13:37might have more bearing.

13:44There's a giant

13:45hiding out in the kelp.

13:47The grey whale

13:49is not a year-round

13:50inhabitant,

13:51but it's a pretty

13:53impressive visitor.

13:55It's made the 7,500

13:58kilometre journey

13:59from the freezing Arctic

14:00to give birth

14:02in the warmer waters

14:03of Southern California.

14:05This is the longest migration

14:07of any mammal

14:08on the planet.

14:09Now the calf

14:11is strong enough,

14:12they must make their way

14:13back to Arctic feeding grounds,

14:15taking them past

14:16the mouth

14:17of Monterey Bay.

14:19But with a baby in tow,

14:21not only does this journey

14:22become slower,

14:24but far more dangerous.

14:26They're not the only

14:29large predators

14:30out here.

14:32The grey whale

14:33mother has a decision

14:35to make.

14:37It can hug the coast

14:38hiding out

14:39in the cover

14:39of the kelp forest

14:40or cut straight across

14:43the mouth of the bay.

14:45This is the quicker route

14:47but leaves her

14:48and her baby

14:49out in the open

14:50and vulnerable

14:51to attack.

14:52A pack of deadly predators

14:56stalk these waters.

15:00Orchinus orca,

15:01the aptly named

15:03killer whale.

15:06Capable of 50 kilometre

15:08per hour bursts,

15:10the potent predators

15:11have no trouble

15:12catching up

15:12with the slow-moving pair.

15:15But the power of the mother

15:17is not to be underestimated.

15:19Under attack,

15:22grey whales

15:22react violently,

15:26earning them

15:27the name

15:27devil fish

15:28by early hunters.

15:30The killers

15:31must play

15:32to their strengths.

15:35They're a third

15:36of the size

15:37but they have

15:37speed on their side.

15:40By giving chase,

15:42they hope

15:42to tire the calf.

15:46This game

15:47of cat and mouse

15:48can last hours

15:49before the mother

15:51is forced to stop

15:52for her exhausted calf.

15:57Now the pack

15:58combines strength,

16:00forcing themselves

16:04between the whales

16:05and driving them apart.

16:10Once the calf

16:11is separated,

16:12it's all over.

16:14The killer pack

16:19has won.

16:23And the mother

16:24must go on alone.

16:32Battles between

16:33these large animals

16:34might not have

16:35a direct effect

16:36on the balance of life

16:37in the lower reaches

16:38of the forest,

16:39but they're still

16:41vitally connected

16:42to the kelp.

16:48What's left

16:49of the body

16:49of the baby whale

16:50will sink

16:51to the sea floor,

16:54break down,

16:55and then be recycled

16:56back to the surface

16:57by upwellings,

16:58feeding the kelp

17:01and supporting

17:02its tenants.

17:03Perhaps the greatest

17:07impact that large

17:08predators have

17:09on life in the kelp

17:10is by indirectly

17:13contributing

17:13to the nutrient cycle

17:15that helps

17:15to sustain it.

17:19The problem is

17:20that with healthy kelp

17:21comes the animals

17:22that want to eat it.

17:25These aren't just

17:26any grazers.

17:27If we're looking

17:30for a species

17:31that has a real

17:32impact on the kelp,

17:33well,

17:34we've found it.

17:37A herd of sea urchins,

17:40kelp eaters.

17:43They reproduce fast,

17:45doubling their numbers

17:47in a matter of days,

17:48and they're armoured

17:50in spines

17:50that few predators

17:51can break through.

17:54This is an army

17:55built for a purpose.

17:57Unlike other grazers,

18:01urchins aren't only

18:02interested in the kelp's blades.

18:07Five sets of brutal,

18:09self-sharpening

18:10calcium carbonate teeth

18:12hit the kelp

18:13where it hurts most.

18:17The hold fast

18:18may be tough enough

18:19to withstand winter storms,

18:21but it's no match

18:24for the urchin's jaws.

18:27These are capable

18:28of chomping through rock.

18:40By feeding at the base,

18:42sea urchins can cut

18:43entire spires loose

18:45and are capable of destroying

18:51whole beds of kelp

18:52at a time.

18:58Yet, despite this onslaught,

19:00the kelp proliferates.

19:02not because, even with nutrient-rich waters,

19:06it can outgrow urchin grazing,

19:10but because it also supports

19:13another species,

19:15a creature equally ravenous.

19:20floating at the surface

19:25lies the secret

19:26to the success

19:28of the bay.

19:32A raft of sea otters

19:33have rolled themselves

19:35in the kelp's fronds,

19:37anchoring themselves in place

19:39so they don't drift out to sea

19:40while they sleep.

19:41This may be the smallest sea mammal,

19:48but with a voracious appetite

19:51and a partiality

19:52for urchin meat,

19:54it's crucially important

19:56to the kelp forest.

20:00With an adult typically eating

20:02up to 30% of its body weight

20:04a day,

20:05that could be 50

20:09of the spiny invaders.

20:12The otter is Monterey Bay's

20:13secret weapon

20:14of mass urchin destruction.

20:21Although the urchins

20:22are typically found

20:23on the sea floor,

20:25otters make light work

20:26of finding them.

20:30Holding their breath

20:31for five minutes,

20:33they'll dive up to 18 metres

20:36prizing urchins

20:44off the rocky seabed.

20:51Sea otters

20:52aren't just effective hunters,

20:54they're also brilliant tool users.

20:57Cracking open

20:58their prey's shell

20:59by banging it

21:00against a flat stone

21:01on their stomach.

21:03A clever way

21:04of getting past

21:04those sharp spines,

21:08munching

21:08on its protein-rich innards.

21:13Mothers pass on

21:14hunting techniques

21:15to their pups,

21:16although they can

21:20take a while

21:20to perfect.

21:24So many species

21:26rely on the kelp

21:27and therefore

21:28the otter's appetite,

21:29which keeps the urchins

21:30in check.

21:31But the question remains,

21:34why do the otters

21:35need to eat

21:36quite so much?

21:39Unlike their neighbours,

21:40the harbour seals

21:41and sea lions,

21:43otters don't have

21:44a thick blubber layer,

21:46which is the usual defence

21:47against cold water.

21:49This means that

21:50their body heat

21:51is constantly being lost

21:52to the water around them.

21:55Otters combat this

21:56in two ways.

21:57Firstly,

21:59with their fur,

22:00the densest fur

22:01of any animal

22:02on the planet.

22:05Up to a million hairs

22:07in an area

22:08the size of a postage stamp,

22:11trapping air,

22:12keeping the cool water

22:13at bay

22:13and providing insulation.

22:19Their loosely jointed skeleton

22:21means they're flexible enough

22:22to fluff air back

22:23even into those

22:24tough-to-reach places.

22:25In fact,

22:28this system works

22:29so well

22:30that with careful grooming

22:31cold water

22:32never reaches

22:33the skin at all.

22:34This remarkable fur

22:44goes a long way

22:45to keeping them warm.

22:47But to keep their core

22:49internal temperature up,

22:50they must constantly

22:51burn energy.

22:54And that means

22:55consuming calories.

22:59Lots of them.

23:00Urchin control,

23:04crucial as it is

23:06to the kelp,

23:07is really just

23:08a side effect

23:09of otter thermoregulation.

23:12Although populations

23:14of sea otters

23:15are relatively small,

23:17they're critical

23:18to the balance

23:19of the ecosystem.

23:21So they are what is known

23:23as a keystone species,

23:25guardians of the kelp forest.

23:28The importance

23:31of sea otters

23:32to the balance

23:32of the ecosystem

23:33hasn't always been known.

23:36Sadly,

23:37it was learnt

23:38the hard way.

23:42When settlers

23:43first arrived

23:44on California's coast,

23:45they treated the ocean

23:47like an open larder.

23:49Few species

23:50were safe

23:51and the otter

23:53fared worst of all.

23:57It's a sad irony

23:59that the beautiful adaptation

24:00that made them

24:01so suited

24:02to life in the bay

24:03put sea otters

24:04at the brink

24:05of extinction.

24:09Otters were hunted

24:10so heavily

24:11for their pelts

24:12that within 100 years

24:14they'd vanished

24:15from California's coastline.

24:16For scientists,

24:20it was a living demonstration

24:22of the key role

24:23that otters play.

24:26With the keystone species removed,

24:30urchin numbers rocketed,

24:34devouring the kelp.

24:35In several areas

24:41along the Californian coastline,

24:44the forests

24:44disappeared altogether.

24:51Once sea urchins

24:52have cleared

24:53an area of kelp,

24:54enough numbers

24:55will remain

24:55in this barren area

24:57to nip any regrowth

24:59in the bud.

25:00These urchin barrens

25:02were an ecological disaster.

25:05Coastal fish

25:10and invertebrate populations

25:11in Monterey

25:12plummeted.

25:17And so,

25:18large predators

25:19were forced

25:20to move away.

25:25Although otter hunting

25:27was officially banned

25:28in 1911,

25:30it was too late.

25:32No otters

25:33had been seen

25:34in the area

25:34in living memory,

25:37considered extinct.

25:41Monterey Bay

25:42had lost its key.

25:52Until a chance glance

25:54down a telescope

25:55in 1938

25:57turned the fates

25:58for this failing ecosystem.

26:01A secret community

26:03up to 300 animals strong

26:05living in a remote bay.

26:08No one knows

26:09how this fortunate

26:10community survived,

26:12but their discovery

26:13heralded a new dawn

26:14for Monterey Bay.

26:19Scientists had seen

26:21what happened

26:21to the ecosystem

26:22when the keystone species

26:23was removed.

26:24Now they had the unique

26:27opportunity

26:28to watch the effects

26:29of its return.

26:31With hunting banned,

26:33this otter population

26:34grew,

26:35getting down

26:36to some serious

26:37urchin eating,

26:39which gave kelp beds

26:42a chance to take hold

26:43and grow.

26:44With such a ready

26:48supply of food,

26:49the secret population

26:50of hundreds

26:51became thousands

26:53and showed

26:55that where the otter went,

26:57healthy kelp followed.

27:03Monterey's keystone species

27:05was recovering,

27:06allowing the ecosystem

27:14to recover with it.

27:18Link by link.

27:22Today, Monterey Bay

27:23is once again

27:24one of the most diverse

27:26marine habitats

27:27on Earth.

27:30It's a real

27:31ecological success story.

27:33We've seen

27:36just how complex

27:37the web of life

27:38is here

27:39and how quickly

27:41it can fall apart.

27:44So it's crucially

27:45important

27:46that the bay

27:46is protected.

27:48And with its

27:49otter guardians

27:50in place,

27:51keeping urchin grazers

27:52under control,

27:54the future

27:54looks bright

27:56for Monterey.

27:59The balance

28:00has returned.

28:03The kelp forest

28:04and its tenants

28:05are thriving.

28:13The hope is

28:14that by protecting

28:15these waters

28:16and its

28:17keystone species,

28:19this diverse

28:22marine ecosystem

28:23will continue

28:25to be

28:26spectacular.

28:33Day 5 action

28:35from the Gold Coast

28:36next on BBC4,

28:38it's Commonwealth Games Extra.

28:40Then BBC4 brings you

28:42a brand new

28:43Art Lover's Guide

28:45to the Portuguese capital,

28:47Lisbon,

28:48in an hour.

28:48the

29:17of the

Microworlds 04of13 Monterey Bay

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