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It remained a mystery
for a thousand generations...

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capturing the imagination

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of those who lived
at its edge

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but could not visit there.

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Who could see only dimly
into a shadowy world

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both beautiful and bizarre.

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Today, we can enter that world

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and cast light on it.

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Scientific explorers now seek
to uncover

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the secrets of this world.

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Some of what we've learned
seems remarkably similar

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to the beliefs of Australia's
aboriginal people.

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They have endured
for 50,000 years

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by regarding themselves not
above nature, but part of it.

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Science often takes
a different approach...

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analyzing the living world
by dissecting it

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species by species.

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But the aboriginals believe
that no living thing

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exists apart from the greater
community of living things

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that even the human
is merely a part

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of the great system of life.

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Science is only now discovering

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how much the aboriginals
have long understood.

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"It was unchanged through
all of the time of my ancestors.

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"From the dreamtime
when animals were almost human

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"and people were gods,

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unchanging.

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"The sea, the reef
and all that lives here.

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"But now,
people are no longer gods

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and change encircles us
like the sharks."

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The encroaching modern world is
symbolized by vast settlements

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such as Sydney,
Australia's largest city.

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But along the same coast lies
an ancient underwater city

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called by aboriginals
Wogogaboo.

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It is the largest structure
on earth

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built by living things.

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The Great Barrier Reef.

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More than 2,000
identifiable reefs combine

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to form a rampart of coral
1,200 miles long

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extending as much as 120 miles
out to sea.

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Erected over millions of years

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it is a feature
of earth's surface so immense

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as to be visible from the moon.

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In the great liquid space
of the ocean

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the reef's limestone ramparts
and towers loom up

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like a vast housing complex,
providing its residents

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with shelter
from the surging sea

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and from one another.

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Like human cities,
the reef is also a place

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where the hungry
can find a meal.

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The concentration
and interaction of life here

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makes possible a steady exchange
of life-giving nutrients

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gathered from
the surrounding sea.

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Ironically, the massive
reef system owes its existence

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to tiny creatures
called coral polyps.

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Though these diminutive
construction workers

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are plant-like in appearance,
they are animals

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related to jellyfish
and sea anemones.

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They feed by capturing
passing food in their tentacles

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and protect themselves
by secreting

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a casing of calcium carbonate.

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The calcium remains
of the polyps

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are compressed over time
into limestone

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forming the foundations

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upon which new coral generations
build.

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An oasis
in the desert of the open sea

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the reef city attracts
offshore travelers

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like the gentle manta ray.

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Such visitors enter a world
of curious life-forms

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where things are not always
what they seem

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a world where fish can inflate
themselves like balloons

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and an eight-legged creature,
long portrayed as a monster

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turns out to be
remarkably intelligent and shy.

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What appear to be ferns are
instead, animals

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sweeping the water
for bits of food.

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Here, some mollusks
are jet-propelled...

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and worms perform
like Spanish dancers.

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A creature
shaped like a fierce snake

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is actually a fish so wary
it hides in a hole all day.

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What appear to be feathers
are poisonous spines.

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A pink carnation
is actually a worm.

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The corals themselves exist

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in an enormous array
of shapes and configurations.

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Many of these structures
enable them to capture plankton

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in barren tropical waters.

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But to in ensure
a steady food supply

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some corals also grow
their own food...

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a microscopic algae

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cultivated within the tissue
of the cords themselves.

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To provide their algae gardens
with sunlight

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corals take on unusual shapes.

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The more surface area
exposed to the sun

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the better internal algae
gardens grow.

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As the coral generations
accumulate

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they rise toward the surface

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creating a wall
between land and sea

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the barrier which gives
this reef its name.

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This upward growth is not
without risk.

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Occasional drops in sea level
expose and kill the corals

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turning reefs to islands.

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One such tiny slip of land,
Heron Island

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at the southernmost end
of the Great Barrier Reef

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is home to a research station

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operated by
the University of Queensland.

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Scientists from around the world
gather here

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to study the reef ecosystem.

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In the station's labs,
marine biologists seek to learn

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how life transpires

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in the world's greatest
underwater city.

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Perhaps the most important
scientific research takes place

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not in the labs,
but on the reef itself.

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Researches by the score visit
the Great Barrier Reef annually.

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Australians Valerie and Ron
Taylor have devoted their lives

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to underwater exploration
and photography.

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In three decades of diving here

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they have helped reveal

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the enormous complexity
of reef life.

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Although we dive the reef
in the name of science

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to study, photograph and count

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the sheer beauty of the place
draws us here

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as much as the desire
to better understand it.

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The corals form a habitat

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as lovely and magical
as a fairy-tale setting.

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For life here, though

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the coral serves as a vital
framework for survival

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providing catch holds
for attaching organisms

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hiding places for prey and
hunting grounds for predators.

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A single square meter of coral
can sustain dozens of species.

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The coral polyps are
the landlords

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extracting as rent the organic
debris of their tenants.

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The tiny blenny keeps
a wary watch

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from the reef equivalent
of an apartment.

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Moray eels seek out crevices
to occupy like day rooms.

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Like many residents

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the barramundi cod lays claim
to a plot

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and spends much of its time
defending it from intruders.

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Some creatures,
like these bat fish

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use the reef as a place to hover
and rest part of each day.

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Many of the fish that swim
lightly through the day

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commute beyond the reef
at night to hunt

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changing places with others
that commute back

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to rest all night on the reef.

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The constant search for food
permeates existence here.

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Hunger can even lead small fish

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to risk approaching
a much larger stranger

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in the hope of finding
something to eat.

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Offer food, and the fish flock
like birds in a city park.

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Not every creature here is
a resident.

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The jellyfish is a passer-by

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occasionally swept over the reef
as it rides the currents.

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Most animals,
like the shovel-nosed skate

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seem timid
in the presence of divers.

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But the Taylors have learned
to be on the lookout

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for a notorious creature
less likely to flee.

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The abundance that draws divers
to the reef

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also attracts sharks.

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Some sharks
are permanent residents

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who survive by being masters
of deception.

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The wobbegong, or carpet shark

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has developed
near-perfect camouflage

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making it difficult to tell
coral from carnivore.

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It escapes the notice of enemies
while lying in ambush for prey.

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Because of their long experience
diving the reef

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the Taylors have often led
scientific expeditions

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to study
the deepwater sharks lured

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to this rich hunting ground.

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Though frenzies are believed
uncommon

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sharks grow aggressive
when food is on their midst

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whether provided by nature

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or by humans seeking
to observe their behavior.

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These bronze whalers provide
a rare glimpse

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of the streamlined power of
animals fashioned by evolution

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into beautiful and near-perfect
hunters in the sea.

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Patrolling the edges of the reef

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sharks serve a vital function.

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They eliminate the weak

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and, over time,
strengthen the breeds

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of the very species
they prey upon.

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The history of the reef is a
chronicle of constant change.

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More than 25 million years ago

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corals began to fringe
Australia's eastern coast.

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Across eons,
ice ages lowered the sea levels

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exposing and killing reef coral
until the climate began to shift

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and global warming melted
the ice

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allowing fresh veneers of coral
to return.

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Though most of the reef's story

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remains hidden
beneath the surface

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we can more readily trace
the history

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of the scattered islands
looming up from it.

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When the seeds and spoors
of life

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reach these fertile outposts
on the wind or currents

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lush miniature worlds are born.

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The islands provide
both sustenance and habitat

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for some of the largest bird
colonies in the tropics.

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The life of the islands
is inextricably linked

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to the encircling sea.

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00:19:19,244 --> 00:19:23,810
Nutrients are cycled
from fish to bird to guano

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fertilizing
luxuriant vegetation.

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00:19:58,219 --> 00:20:00,246
These islands are also
the birthplace

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of another creature of the sea.

201
00:20:03,461 --> 00:20:07,731
Each year, on summer's tides,
under the protection of night

202
00:20:07,870 --> 00:20:11,810
and ancient drama
of reproduction unfolds.

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00:20:15,985 --> 00:20:19,720
From birth,
sea turtles are ocean wanderers.

204
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But at the age of 30,
they begin to return every year

205
00:20:24,401 --> 00:20:26,769
across thousands of miles
of open sea

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00:20:26,906 --> 00:20:29,376
to reproduce young of their own

207
00:20:29,511 --> 00:20:32,677
on the very same beaches
where they were born.

208
00:20:37,226 --> 00:20:38,751
After mating at sea

209
00:20:38,895 --> 00:20:42,198
the female laboriously pulls
herself ashore

210
00:20:42,336 --> 00:20:45,136
where she digs an egg chamber
in the sand.

211
00:20:46,377 --> 00:20:50,510
In a single night, she will lay
as many as 180 eggs

212
00:20:50,652 --> 00:20:53,623
then cover them with sand
and return to the sea.

213
00:20:54,726 --> 00:20:57,823
The hidden eggs incubate
over eight to ten weeks

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00:20:57,966 --> 00:21:02,168
protected by sand from sea birds
and other marauders.

215
00:21:18,872 --> 00:21:20,535
When the hatching emerge

216
00:21:20,676 --> 00:21:23,203
instinct propels them
toward the ocean

217
00:21:23,347 --> 00:21:26,410
in a race
to escape island birds.

218
00:21:35,270 --> 00:21:37,934
Perhaps only one in a thousand
of these hatchlings

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00:21:38,075 --> 00:21:41,104
will return in 30 years
to reproduce...

220
00:21:41,249 --> 00:21:45,313
enough to ensure
the perpetuation of the species.

221
00:21:54,707 --> 00:21:56,768
Beyond the marvels
of ocean life

222
00:21:56,911 --> 00:21:59,246
researchers are also
making discoveries

223
00:21:59,383 --> 00:22:03,345
that could yield invaluable
products for human life.

224
00:22:03,491 --> 00:22:06,018
Scientists are
already finding species here

225
00:22:06,162 --> 00:22:08,929
with immunities
against many diseases.

226
00:22:19,054 --> 00:22:21,456
The reef is a kind
of living laboratory

227
00:22:21,592 --> 00:22:24,655
where survival prompts
exotic adaptations.

228
00:22:32,579 --> 00:22:33,774
Juvenile fish

229
00:22:33,915 --> 00:22:36,010
developed from eggs drifting
in the currents

230
00:22:36,153 --> 00:22:37,816
congregate near the reef.

231
00:22:39,360 --> 00:22:40,384
When mature

232
00:22:40,528 --> 00:22:43,330
they move out together
as schools.

233
00:22:54,154 --> 00:22:55,486
The shimmering array of fish

234
00:22:55,623 --> 00:22:58,026
and the ability
of every individual in a school

235
00:22:58,162 --> 00:23:01,361
to instantly
and simultaneously shift course

236
00:23:01,501 --> 00:23:05,498
presents a disorienting target
to would-be predators.

237
00:23:27,152 --> 00:23:29,782
A diver roaming the reef
will encounter

238
00:23:29,923 --> 00:23:31,586
as many strategies
for self-defense

239
00:23:31,727 --> 00:23:35,461
as there are potential dangers
in the surrounding sea.

240
00:23:39,107 --> 00:23:40,770
For those creatures not blessed
with great speed

241
00:23:40,911 --> 00:23:45,044
a suit of armor can provide
a portable hiding place.

242
00:24:11,102 --> 00:24:13,334
For invertebrates
such as the lobster

243
00:24:13,473 --> 00:24:18,244
a shell serves a dual purpose
as both shield and skeleton.

244
00:24:33,544 --> 00:24:35,137
Lacking a shell of its own

245
00:24:35,281 --> 00:24:37,717
the hermit crab turns
an empty shell

246
00:24:37,852 --> 00:24:40,119
into a kind of mobile home...

247
00:24:45,401 --> 00:24:48,999
while the spider shell fashions
a shelter camouflaged

248
00:24:49,141 --> 00:24:51,338
to be mistaken for coral.

249
00:24:59,795 --> 00:25:02,197
No method of defense
is foolproof.

250
00:25:03,469 --> 00:25:05,404
A crab suddenly caught
in the open

251
00:25:05,539 --> 00:25:07,304
is vulnerable to attack.

252
00:25:11,851 --> 00:25:14,344
Opportunistic predators
quickly zero in

253
00:25:14,489 --> 00:25:16,721
on the crab's
vulnerable underbelly.

254
00:25:55,268 --> 00:25:58,364
The hard limestone casing
secreted by corals

255
00:25:58,507 --> 00:26:00,943
provides polyps
with a secure shelter

256
00:26:01,079 --> 00:26:03,208
impervious to most predators.

257
00:26:05,086 --> 00:26:08,287
Yet, there is
one devastating exception

258
00:26:09,461 --> 00:26:12,126
the crown-of-thorns starfish.

259
00:26:16,308 --> 00:26:19,108
Emitting digestive juices
that kill polyps

260
00:26:19,247 --> 00:26:21,945
the crown of thorns
can wreak havoc.

261
00:26:24,423 --> 00:26:26,484
In occasional
population explosions

262
00:26:26,628 --> 00:26:30,066
that ravage immense tracts
of the Great Barrier Reef

263
00:26:30,200 --> 00:26:33,105
the crown of thorns
literally eats itself

264
00:26:33,241 --> 00:26:35,107
out of house and home.

265
00:26:48,736 --> 00:26:50,330
The crowded conditions
of the reef

266
00:26:50,473 --> 00:26:51,703
have prompted organisms

267
00:26:51,843 --> 00:26:55,042
to develop elaborate
chemical weaponry.

268
00:27:03,932 --> 00:27:07,770
Nudibranchs, defend themselves
simply by tasting bad.

269
00:27:12,716 --> 00:27:14,583
To advertise
their distasteful nature

270
00:27:14,720 --> 00:27:16,119
and discourage predators

271
00:27:16,255 --> 00:27:18,623
they've developed
gaudy color schemes

272
00:27:18,760 --> 00:27:20,957
illustrating a rule
of the reef...

273
00:27:21,098 --> 00:27:23,729
bright colors mean,
"Don't eat me"

274
00:27:23,870 --> 00:27:27,274
which may explain why there are
so many colorful creatures here.

275
00:27:52,725 --> 00:27:56,529
The florid beauty
of the anemone can be deceptive.

276
00:27:56,667 --> 00:27:59,331
Capsules on the tentacles
of some anemones

277
00:27:59,471 --> 00:28:00,906
fire poison darts

278
00:28:01,042 --> 00:28:04,914
that paralyze anything,
from plankton to fish.

279
00:28:09,223 --> 00:28:11,888
Yet, small clown fish
have adapted

280
00:28:12,029 --> 00:28:14,158
to living
within the deadly weaponry

281
00:28:14,300 --> 00:28:16,497
protected by a mucous coat.

282
00:28:18,575 --> 00:28:20,806
The clown fish escape predators

283
00:28:20,946 --> 00:28:23,884
by remaining close
to the stinging anemone

284
00:28:24,019 --> 00:28:26,546
even using it as an egg nest.

285
00:28:27,191 --> 00:28:29,559
In turn,
the nearly immobile anemone

286
00:28:29,695 --> 00:28:32,098
can capture
and eat curious predators

287
00:28:32,234 --> 00:28:33,634
lured to its side

288
00:28:33,770 --> 00:28:36,435
by the presence
of the tiny clown fish.

289
00:28:48,967 --> 00:28:51,699
The lion fish displays
the bright coloration

290
00:28:51,838 --> 00:28:53,671
of a chemical warrior.

291
00:28:54,176 --> 00:28:57,239
The feather-like spines contain
a powerful toxin

292
00:28:57,382 --> 00:29:01,083
capable of paralyzing
or killing an attacker.

293
00:29:23,933 --> 00:29:25,197
Among the most venomous

294
00:29:25,336 --> 00:29:28,274
of all marine creatures is
the puffer fish

295
00:29:28,409 --> 00:29:29,843
best known for swelling up

296
00:29:29,978 --> 00:29:32,141
to make itself difficult
to swallow.

297
00:29:38,126 --> 00:29:41,930
Many puffers also carry
a nerve poison in their organs

298
00:29:42,068 --> 00:29:44,664
so powerful
that predators risk death

299
00:29:44,806 --> 00:29:47,972
from respiratory paralysis
if they eat a puffer.

300
00:29:54,458 --> 00:29:57,327
The study of reef toxins
has already shed light

301
00:29:57,465 --> 00:29:59,799
on the nature of nerve
and muscle disorders.

302
00:30:00,870 --> 00:30:01,564
We may find

303
00:30:01,705 --> 00:30:03,674
that substances deadly
on the reef

304
00:30:03,809 --> 00:30:05,334
can be turned by science

305
00:30:05,479 --> 00:30:08,508
into remedies
for human ailments.

306
00:30:22,947 --> 00:30:26,544
At night, the mood
of the reef transforms.

307
00:30:27,221 --> 00:30:29,748
Shifts change in the reef city.

308
00:30:32,831 --> 00:30:35,632
Herbivores that graze by day
are replaced

309
00:30:35,770 --> 00:30:37,797
by carnivores
that hunt by night.

310
00:30:39,143 --> 00:30:41,478
None is better equipped
than the shark.

311
00:31:21,491 --> 00:31:24,657
In complete darkness,
the shark can locate prey

312
00:31:24,798 --> 00:31:29,067
by sensing the electrical fields
of quarry and homing in on them.

313
00:31:35,417 --> 00:31:38,686
In the sea, the shark is master
of the night.

314
00:31:51,915 --> 00:31:53,282
For many creatures

315
00:31:53,419 --> 00:31:57,086
night is simply a time
of inactivity, and even sleep.

316
00:31:58,528 --> 00:32:01,295
The crevices and corridors
of the reef city offer

317
00:32:01,435 --> 00:32:04,133
a profusion of hiding places
for the drowsy.

318
00:32:09,116 --> 00:32:10,846
To rest in safety

319
00:32:10,986 --> 00:32:14,948
the parrot fish surrounds itself
with a mucous cocoon

320
00:32:15,093 --> 00:32:17,086
a transparent sleeping bag

321
00:32:17,230 --> 00:32:19,599
that hides its scent
from night hunters.

322
00:32:29,855 --> 00:32:33,089
Too skittish to be approached
closely in daylight

323
00:32:33,228 --> 00:32:35,061
the creature is so docile
at night

324
00:32:35,199 --> 00:32:37,328
it can be examined carefully

325
00:32:37,469 --> 00:32:39,996
then returned
to its sleeping chamber.

326
00:33:05,657 --> 00:33:09,255
Tentacles retracted all day
by many corals

327
00:33:09,397 --> 00:33:12,893
are now extended
to sting and capture plankton.

328
00:33:14,007 --> 00:33:15,202
The reef comes alive

329
00:33:15,342 --> 00:33:18,109
with millions
of Medusa-like tentacles.

330
00:33:30,505 --> 00:33:32,337
A few nights each year

331
00:33:32,474 --> 00:33:35,914
the Great Barrier Reef is
the scene of a mass spawning

332
00:33:36,049 --> 00:33:38,315
that may be unparalleled
on Earth.

333
00:33:42,996 --> 00:33:44,965
Billions of coral polyps

334
00:33:45,100 --> 00:33:47,297
across thousands
of square miles

335
00:33:47,438 --> 00:33:51,171
spew a storm of eggs and sperm
into the water

336
00:33:51,310 --> 00:33:53,543
often within minutes
of one another.

337
00:33:55,953 --> 00:33:58,618
The floating blizzard
of new life is attacked

338
00:33:58,759 --> 00:34:02,755
by a frenzy of worms
and countless tiny predators

339
00:34:05,137 --> 00:34:06,629
but enough spawn survive

340
00:34:06,774 --> 00:34:09,176
to create
a new coral generation.

341
00:34:11,649 --> 00:34:14,587
The spawn will drift far
before sinking.

342
00:34:15,090 --> 00:34:18,790
The progeny of one reef
can ensure the future of others

343
00:34:18,930 --> 00:34:20,091
far in the distance.

344
00:34:24,608 --> 00:34:29,050
Lighthouses and markers reveal
an ominous side of the reef.

345
00:34:29,184 --> 00:34:33,682
Though a haven for sea life,
it is a mortal enemy of ships.

346
00:34:35,530 --> 00:34:38,433
Even steel hulls
can be ripped open

347
00:34:38,568 --> 00:34:40,231
by hidden coral heads.

348
00:34:50,191 --> 00:34:52,457
There have been
more than 1,200 shipwrecks

349
00:34:52,595 --> 00:34:55,065
on the Great Barrier Reef
in this century alone.

350
00:34:57,237 --> 00:35:00,733
The freighter Cooma
went aground in 1926.

351
00:35:02,447 --> 00:35:06,011
To divers, its crumbling remains
are a haunting reminder

352
00:35:06,154 --> 00:35:08,386
that it once served
as a human home.

353
00:35:10,295 --> 00:35:12,162
Yet, to creatures of the sea

354
00:35:12,299 --> 00:35:14,792
the sunken ship is merely
a new building site.

355
00:35:21,951 --> 00:35:25,651
Legions of polyps
and other encrusting colonizers

356
00:35:25,791 --> 00:35:30,426
gradually overwhelm deck plates
and superstructures in a process

357
00:35:30,568 --> 00:35:33,004
that will ultimately entomb
the steel remains

358
00:35:33,139 --> 00:35:37,546
beneath layers of life,
creating an artificial reef

359
00:35:37,681 --> 00:35:40,244
to be settled like a new suburb
of the city.

360
00:36:06,169 --> 00:36:08,731
Researchers have assumed
a leading role

361
00:36:08,873 --> 00:36:11,105
in the preservation
of this ecosystem.

362
00:36:11,880 --> 00:36:13,781
They have been
directly responsible

363
00:36:13,917 --> 00:36:16,855
for the protection
of many threatened species.

364
00:36:17,992 --> 00:36:18,925
Through the efforts

365
00:36:19,060 --> 00:36:21,587
of many concerned people
like the Taylors

366
00:36:21,733 --> 00:36:24,226
the Great Barrier Reef
was established

367
00:36:24,371 --> 00:36:27,206
as a marine park
by the Australian government.

368
00:36:33,588 --> 00:36:34,887
The Great Barrier Reef

369
00:36:35,025 --> 00:36:37,222
is a monument to life.

370
00:36:37,362 --> 00:36:40,801
Tiny living organisms
built it all,

371
00:36:40,935 --> 00:36:45,035
created a reef larger
than all the structures of Man.

372
00:36:45,811 --> 00:36:48,647
We have only glimpsed
the astonishing diversity

373
00:36:48,784 --> 00:36:50,616
and complexity of its life.

374
00:36:53,059 --> 00:36:54,789
We find wonder and beauty

375
00:36:54,928 --> 00:36:57,331
in something as simple
as a hermit crab.

376
00:36:58,302 --> 00:37:01,239
It is important
that we share that wonder

377
00:37:01,375 --> 00:37:03,811
that we care
for this priceless heritage

378
00:37:03,946 --> 00:37:06,610
for ourselves, for our children

379
00:37:06,751 --> 00:37:08,983
for all the generations to come.

380
00:37:16,337 --> 00:37:19,968
We are learning more and more
about the Great Barrier Reef

381
00:37:20,110 --> 00:37:23,379
and the myriad species
which exist within it.

382
00:37:23,517 --> 00:37:25,817
Yet here, perhaps

383
00:37:25,955 --> 00:37:30,157
we may learn most
about our own species.

384
00:37:33,936 --> 00:37:38,001
On the reef, we may learn
whether we are only a predator

385
00:37:38,145 --> 00:37:40,672
grown so powerful and uncaring

386
00:37:40,816 --> 00:37:43,948
as to harm a magical realm
of life

387
00:37:44,090 --> 00:37:46,754
or whether, with all our powers

388
00:37:46,895 --> 00:37:50,163
we have grown
to respect life in all its forms

389
00:37:50,334 --> 00:37:55,242
and to leave all
its splendid torches burning.

390
00:37:59,418 --> 00:38:01,786
All living things are one

391
00:38:01,924 --> 00:38:04,794
like the blood
which unites one family.

392
00:38:05,931 --> 00:38:09,268
All of life forms one great web.

393
00:38:09,939 --> 00:38:12,706
Man did not weave the web
of life.

394
00:38:13,746 --> 00:38:16,046
He is only a part of it.

395
00:38:16,686 --> 00:38:19,851
He is only a strand within it.

396
00:38:20,258 --> 00:38:22,992
Whatever he does
to the web of life

397
00:38:23,832 --> 00:38:27,363
he does to himself.