Coral Seas The Blue Planet


Coral Seas

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In all the seas of the world,

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the warm waters of the Tropics contain the richest and most colourful communities.

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Coral reefs. They may seem like underwater paradise,

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but they are perpetual battlegrounds for space.

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Even the corals have to fight for it.

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In this crowded, frenetic community, every individual has to find its own place, its own way of surviving.

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But none of these creatures would be here, if it were not for the coral.

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A coral larva drifts in the open sea, floating in a soup of young reef animals.

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If just one of these coral larvae settles in a suitable spot and survives,

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a new reef will be founded.

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In just a few days, the larva changes form and becomes a polyp, similar to a sea anemone.

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Identical copies bud off, and gradually a colony develops.

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Each polyp surrounds itself with a hard skeleton and from this solid base begins to grow.

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It increases in length by 15 centimetres a year.

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This branching coral is only two years old.

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A mature reef can be thousands.

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Corals provide the foundations on which the entire reef community relies.

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Some organisms, like the Christmas tree worms, live within the coral.

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Others climb out, away from the reef, to filter their food from the water.

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As the community grows, intimate relationships are formed

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and different creatures become dependent on one another.

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Even animals that spend much of their time travelling in the open ocean

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return to the reef for a clean.

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Coral reefs can be home to astounding numbers of fish.

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Here swim the smallest and the largest fish in the sea.

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Whale sharks are only visitors.

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When currents bring nutrient-rich water up from the deep, they come here to feed.

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All these animals are here because of the coral.

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This extraordinary complex maze is built layer upon layer

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by millions and millions of individual animals...

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..polyps.

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Each polyp's flesh is supported by a limestone skeleton.

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Below the gut...

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..is the place where most of the growth occurs.

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Here the living tissue deposits an intricate lattice of limestone.

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Beneath that, the limestone skeleton is bare, having been vacated by the living coral tissues.

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This is the hard structure that forms the foundation of the reef.

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And a single reef can extend for many miles.

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Coral reefs are only found in the clear, warm, shallow waters of the tropics.

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Sunlight is vital to them,

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even though they're animals,

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because inside their flesh live millions of tiny single-celled algae...

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plants.

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And all plants need sunlight to photosynthesise sugars.

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98% of the food that corals consume is produced by the algae.

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Without them, the reef would not exist.

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Like any other plant, algae need just the right amount of light,

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not too much, not too little.

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The corals regulate that

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with pigments that we can only see when they are illuminated by ultraviolet light.

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Most corals, for protection, spend the day withdrawn into their stoney fortresses.

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Even then, they're not safe from the jaws of these butterfly fish.

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At night, the corals take in water, expand their tentacles, and emerge to feed.

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They collect plankton.

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Each tentacle has batteries of stinging cells which fire on contact.

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Once the prey is caught, it's passed down to the polyp's mouth.

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It's at night when the polyps are extended that they add to the limestone foundations beneath them.

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Inevitably, the corals begin to overgrow each other and that means trouble.

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When neighbours get too close, they detect one another's presence chemically.

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The aggressor, on the right, prepares for battle.

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The polyps extrude their guts...

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and simply digest their rivals alive.

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A no-man's land, a band of white skeleton, is the only evidence of the night's border dispute.

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Some corals are targeted by yet more deadly predators.

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Predators that can crawl in search of their victims.

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Crown of thorns starfish - poisonous, invincible eating machines.

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They also extrude their gut and digest coral wholesale.

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But some corals have help.

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Small crabs living within their branches resist these onslaughts and defend their home.

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They launch an attach on the vulnerable underside of the starfish.

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Even the crown of thorns will retreat from such a determined attack and this coral is left unharmed.

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Hump-head parrot-fish, nearly a metre and a half in length.

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Their jaws are so powerful they can bite through rock.

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When they descend to feed, the reef itself is under threat.

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They are indiscriminate feeders, taking both rock and coral alike in their quest for algae.

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These fish play a large part in the erosion of the reef.

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The rock and coral they swallow emerges later as a fine sand.

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On a single reef, they can produce tonnes of it every year.

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This soft sand forms the tropical beaches that we find so alluring.

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Over time, the sand builds up to form an island, which is then colonised by animals and plants.

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Trees take root.

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Birds arrive.

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The guano from thousands of terns which have chosen to nest here

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enriches the sandy soil, which then can support more plants.

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But these terns, like other sea birds, depend on the ocean for their food.

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Below water on the reef, there is not only competition for living space,

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but a continual contest between predators and prey.

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It's the arms race between them that, over millions of years,

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has produced today's extraordinary diversity of form.

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Jacks are one of the key predators on the reef.

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Their weapon is speed.

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They seek silversides and THEIR defence is to congregate in confusing shoals of shimmering silver.

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The jacks deal with that by herding the silversides onto the reef.

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Here the jacks have a better chance of separating individual fish from the shoal.

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The jacks can now catch the isolated individuals with lightning attacks.

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It's far safer to be hidden on the reef itself, within the tunnels of a sponge, for example.

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These tiny shrimp are no bigger than grains of rice.

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These shrimps are unique.

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It's recently been discovered that they have a sophisticated social system, similar to that of bees.

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All members of the colony are the offspring of one female - the queen, who is the only one to produce eggs.

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As in a colony of bees, different individuals are specialised for particular tasks.

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Some are guards and are armed with especially large and powerful claws.

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They are on watch at all times, ready to tackle intruders.

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A polychaete worm. For it, a sponge is an excellent hunting ground.

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In such a maze of tunnels, attack can come at any time from any quarter.

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Once the guards are alerted, the worm loses its advantage.

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Better to retreat intact than risk serious injury.

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The sponge makes a safe home for the shrimps and supplies them with food,

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so that they never need venture outside.

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An establishment that provides for all their needs is clearly well worth defending.

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Just as shrimps guard their home, other animals defend their hunting grounds.

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Glass fish make tempting prey for the red-mouthed grouper.

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Its strategy is to swim slowly amongst them until they no longer see it as a threat.

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There are other fish here too.

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Lion fish are ambush predators, taking their time and watching for the right moment.

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But there isn't room here for two predators.

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The grouper, braving the lion fish's poisonous spines, tries to evict its rival.

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But lion fish are persistent.

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This grouper spent many hours simply defending his hunting patch.

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Some animals prefer to avoid conflict whenever possible.

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These harlequin shrimp, having captured the starfish,

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are taking it back to a safe house beyond the reach of competitors and danger.

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The problem with starfish is that they have minds of their own and five large, sticky arms.

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By the time the shrimps have prised off one arm, another has reattached itself.

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Only by manoeuvring the starfish on to its back, can they have any hope of gaining the advantage.

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Even so, getting it back home

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is a major undertaking.

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The starfish is now a living larder.

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If the shrimps can hang on to it, it will feed them for days to come.

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The top of the reef is usually covered by a thin layer of green algae,

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another living larder, and many fish depend on it.

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Powder blue tangs defend their right to graze on a particular patch.

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But for a larder as well-stocked as this, there is always competition.

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When a shoal of convict tangs decide to graze, little can stop them.

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Powder blue tangs try to keep them off.

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But they are overwhelmed by sheer numbers.

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The territory is stripped of algae in minutes.

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The blue tangs appear to be fighting a losing battle.

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But, eventually, they begin to get the upper hand.

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They persist with their attacks until the marauders are well on their way.

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When night falls, some very strange creatures creep out of crevices

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and crawl over the reef.

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This moving bush is an animal,

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a basket star, which spreads out its arms to catch the night's plankton.

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The reef becomes uncannily tranquil.

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The fish retire, hiding themselves where they can.

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The marbled rays come out to hunt for prey buried in the sand...

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..using electroreceptors to scan the sea bed.

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Their activity attracts sharks.

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White tips.

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At night, when vision is of little use, sharks have a real advantage.

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They can still use both smell and electroreception to track fish.

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These sharks are also hunting for fish concealed within the reef.

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Their slender shape enables them to squeeze through surprisingly narrow gaps.

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There is nowhere to hide.

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Few animals are safe during these feeding frenzies.

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Night after night, the reef animals are subjected to these raids.

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But life on the reef is not just about food.

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It's also about sex.

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There are many different breeding strategies,

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but each is aimed at maximising the number of young that will survive.

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Every afternoon for two months, brown surgeonfish can be seen streaming across reefs

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in the Red Sea.

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They all head for the same place, usually some prominent feature.

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Here they wait for the light to fade.

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Suddenly females within the group make a dash away from the reef to release their eggs.

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They're immediately followed by the quickest and closest of the males,

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all of whom are striving to fertilise the eggs.

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Inevitably others come here to feast on such easy food.

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As the surgeonfish spawn, fusiliers move in above to eat the nutritious eggs.

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These are just the first of many predators which will feed on the eggs and developing larvae

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as they drift in the ocean during the next few weeks.

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Other fish are less casual about their eggs.

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Banded pipe fish stay close to a small chosen area on the reef.

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Every morning at sunrise, the female leaves her sleeping site and swims to find her partner.

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For ten minutes or so, they remain together,

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reaffirming the bond that is essential to their partnership.

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They swim together around his territory in a simple greeting dance.

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Throughout the summer, when the female's eggs are ripe,

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courtship begins in earnest in the early morning.

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It takes time, and after about two hours, they rise together off the sea bed, entwining their bodies.

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The male rubs himself against the female

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stimulating her to release her eggs.

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And now, swiftly, the male takes them.

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The eggs, now stuck to his belly, are patted down to ensure that they stay there.

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The female then leaves him, but every morning she will return for a session of synchronised swimming,

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and so ensure that their bond is maintained.

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Ten days later,

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under cover of darkness, the male shakes his body,

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and the young pipe fish are born.

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Only now are they independent of their parents.

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Since the male takes charge of the eggs when they're laid,

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the female can start immediately producing the next batch.

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Without his help, they'd only breed every 20 days, rather than every 10.

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So, by sharing the work, they're doubling the number of young they can produce in any one year.

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The flamboyant cuttlefish.

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Unlike most cuttlefish, this one spends much of its time walking, not jetting, across the sea bed.

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This is a male.

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He is using his colourful display to try and seduce the larger female,

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who seems unimpressed.

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Eventually, she concedes.

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The final event, the transfer of sperm, is very quick.

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TRUMPETING

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A singing, male, humpback whale.

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Humpbacks are only visitors to the reef.

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After a pregnancy that lasted a year, the females come here to give birth and suckle their newly-born young.

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Their investment in their single offspring is considerable,

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for each female will continue to nurse it for a further 6-12 months.

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The males are here to mate.

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The lone males sing to establish their relative seniority.

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The louder and longer the song, the bigger and stronger the singer.

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The better the song, the larger the male, the more mating opportunities he will get.

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All these different mating strategies have the same aim -

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to ensure that the greatest number of offspring will live long enough to breed themselves.

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Corals also reproduce sexually,

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but being fixed to the sea bed, they can't move to find a mate.

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Somehow they must synchronise their sexual activity

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and they do so using the rise in water temperatures of spring and the phases of the moon.

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A few days after the full moon, in late spring, when tidal currents are at their weakest,

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the corals of the Great Barrier Reef are ready to spawn.

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Some corals are male and release clouds of sperm.

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Nearby, a female will be releasing eggs.

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Other species of coral are both male and female.

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These release packages of eggs

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already prewrapped in sperm.

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Bundles of eggs and sperm float to the surface to mix with others from further along the reef.

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Each kind of coral times its release to a certain hour on a certain night.

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That maximises the chances of cross-fertilisation.

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The fertilised eggs drift away from the reef.

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The stormy season brings real danger to the animals of the reef.

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Lobsters in the Caribbean sense a change in the water.

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The temperature drops and powerful ocean swells disturb the sand.

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Under the cover of darkness,

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they emerge to run before the storm and risk crossing the exposed sand flats

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to seek shelter in deeper water.

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Every year, they make this journey.

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From all over the reef, lobsters come to join the march.

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They conserve energy by travelling in one another's slipstream.

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And there is the added benefit of safety in numbers.

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By daybreak, they've reached the edge of the deep reef and down they go.

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For the rest of the stormy season, they will remain in the shelter of deep water, out of harm's way.

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Sometimes during the stormy season, a hurricane builds.

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And then the very structure of the reef itself is under threat.

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An entire reef can be destroyed by just one big storm.

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Hundreds of years of growth gone in a few hours.

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Out in the ocean, new life continues to develop.

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In time, coral larvae will return to colonise the rubble

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and a new reef will grow on the wasteland.

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To get pictures of sharks requires some care and a good understanding of shark behaviour.

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The Blue Planet team has encountered many of the world's 400 kinds of shark

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and by treating them with caution and respect no-one was attacked.

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One of the richest areas for sharks is in the Pacific waters of the Central Americas -

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the "Island Of The Sharks".

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Our teams filmed both day and night.

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Cameramen Bob Cranston and Peter Scoones have had a lot of experience with sharks,

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and Bob has worked in these waters before.

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They hope to film the feeding behaviour of white tip sharks -

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a medium-sized species which hunts in packs.

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For filming at night, especially sharks in a big area, we needed quite a bit of light.

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Little battery lights wouldn't do.

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We brought in a generator

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and cables coming down to 650 Watt lights.

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I don't think the sharks were disturbed at all by the light.

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These sharks are clued in to little electronic impulses from each other

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and also from the prey.

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To reach this remote location our dive boat had sailed 300 miles off the west coat of Costa Rica

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to the tiny isolated island of Cocos.

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Although it's only six miles long,

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it attracts an enormous concentration of marine life.

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This is a big event.

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This is a place in this vast ocean.

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And the deep water currents come in and hit this island,

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sea mount, whatever you want to call it.

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It upwells,

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brings up nutrients for little fish.

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The bigger fish feed on the little fish and the sharks feed on them.

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The whole food chain is right here.

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We're here to film it.

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With so many different subjects to choose from

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the team made up to four dives a day

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and some of the encounters were quite unexpected.

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Some sharks keep swimming to breathe

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but the white tip reef shark can sit on the bottom

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and pump water across its gills by moving its mouth up and down.

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One morning we woke up and there was this big ship,

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a helicopter on its back deck.

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We negotiated to get some flight time

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and shoot some aerials of Cocos.

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Wonderful, because few have seen Cocos from the air.

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In Cocos's micro-climate it rains almost every day.

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The water has been churning up the sediment near the shore,

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making water visibility unacceptable.

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It was time to move on.

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This is our last evening at Cocos.

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We've had two sunny days out of 18.

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Tomorrow we're gonna take a day off and cruise to Malpelo

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which is a little spot out in this huge ocean.

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It'll be an easy day.

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I need one. It's been 20 days of diving every day.

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I'm worn out.

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Malpelo is a barren volcanic rock 300 miles south of Cocos.

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Bob spent the 36-hour journey doing essential maintenance to his diving equipment.

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The tiny island of Malpelo is inhabited - and not just by seabirds.

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To extend their fishing rights,

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Columbia has placed a permanent garrison on the island.

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The welcome distraction of visitors must have been a relief.

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This precarious rope ladder is the only way onto the island.

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Volcanic cliffs rise straight out of the sea,

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making the shores treacherous.

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Once ashore it's an arduous climb in the extreme heat.

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Those guys who climbed Mount Everest,

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they had sherpas to carry their gear up the mountain.

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It was nice and cool.

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The producer picked the hottest day of the year to climb this rock.

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The volanic rocks of Malpelo soar almost vertically out of the sea bed.

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Deep ocean currents run up against the island

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and rise to the surface,

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carrying a soup of nutrients.

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The result is an oasis of life in a desert of open ocean.

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The fertility of Malpelo attracts an enormous number of predators.

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One of the most impressive spectacles is called a bait-ball.

0:54:320:54:37

A shoal of small fist are corralled into a ball near the surface

0:54:390:54:44

and then attacked by predators such as tuna.

0:54:440:54:47

But bait-balls are unpredictable, and may only last

0:54:470:54:51

a few minutes. Our team were extremely lucky to film this one.

0:54:510:54:57

That wasn't a very big bait-ball.

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Probably only 400-500 fish, about this big around.

0:55:010:55:06

As soon as I jumped in the water, I could hear a roar.

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This sound of scales flying... Bap, bap, bap, bap, bap!

0:55:120:55:18

Yellowfin tuna - wham! Wham! Wham! Silky sharks - smash! Smash!

0:55:180:55:22

And then, in about three minutes,

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it's all over. They ate them all.

0:55:260:55:30

Malpelo was still to hold one more surprise for our crew,

0:55:300:55:35

only discovered when they dived on the other side of the island.

0:55:350:55:40

They'd seen the oceanic silky sharks before, but not in such numbers.

0:55:400:55:45

The silky sharks are a beautiful shark.

0:55:490:55:54

What makes them so fascinating is that there's thousands of them.

0:55:540:55:59

I don't think you have anything to be worried about or frightened of

0:56:020:56:07

if there's no bait in the water.

0:56:070:56:09

If you were to introduce something for them to feed on,

0:56:090:56:13

then they start competing with one another,

0:56:130:56:16

and then you might smell like a fish, and you could get bit.

0:56:160:56:21

But under normal conditions they're a very curious shark.

0:56:210:56:27

They come up to you, which makes it good for photography.

0:56:270:56:31

They bump and push off your camera.

0:56:310:56:34

I think they want to find out what you are and what you're doing here.

0:56:340:56:39

It's a very unique place.

0:56:390:56:42

You're diving on the edge of reality.

0:56:430:56:46

Next week, Blue Planet enters a world governed by the moon -

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a world dominated by tides,

0:57:380:57:41

that spell life and death in the ocean.

0:57:410:57:47

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