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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
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