Recording sights that will astonish even experienced divers, NOVA documents an extraordinary day in the life of the largest coral reef in the world, capturing for the first time the annual spawning of coral and other unusual creatures of the reef.
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00:00Tonight on NOVA, Australia's Great Barrier Reef.
00:05Dive into a world teeming with extraordinary life.
00:10Where males are females, and even the rocks are alive.
00:15Danger lurks at every turn, and only the lucky survive.
00:20A unique journey to a mysterious world of strange and beautiful creatures.
00:26Treasures of the Great Barrier Reef.
00:48There is a mysterious underwater realm where nature has set aside all restraints.
00:56It is a world riddled with labyrinths and chasms.
01:12Predators lurk hungrily.
01:15And swarms of animals, large and small, fill the sea with spectacular combinations of color and form.
01:25Fish create a shifting, three-dimensional kaleidoscope.
01:39While sedentary creatures of every color and description weave a living Persian carpet beneath them.
01:45Here, even the rocks are alive.
01:55Brittle thickets of staghorn coral and undulating sea whips are part of this unearthly cast of characters.
02:03Here, where many animals look like plants, surprises await at every turn.
02:25There are female fish that begin their lives as males.
02:33And snails that are both male and female at once.
02:37There are colors that advertise, and colors that conceal.
02:41Bridium colors that seem to exist simply to dazzle the eye.
02:49This is the enchanted realm of the Great Barrier Reef.
03:01Stretching for more than 1,200 miles along Australia's eastern coast.
03:07The largest community of living organisms on Earth.
03:11It is a lush island of life in an otherwise barren tropical sea.
03:17Life here runs on a strict solar clock.
03:21Its timekeeper is light.
03:24Its driving force.
03:26The need to reproduce.
03:29The need to eat.
03:32And to avoid being eaten.
03:37Even the living structure of the reef, made entirely from coral, perpetuates itself on cues from this clock.
03:45In a silent dance of life that occurs but once a year.
04:01As the first rays of the rising sun filter through the reef,
04:05in the middle of the sea.
04:06Groupers and other hunters of the twilight hours stretch languidly,
04:10and stop their prowling as they ease into comfortable daytime hiding places.
04:21Members of the daylight shift cautiously prepare to abandon their nighttime shelters.
04:26The lingering twilight still offers an advantage to predators, whose tactics work best in dim light.
04:38One of these, a lionfish, glides along the reef, as if secure in the knowledge that venomous spines make it an unpleasant target for others.
04:48Searching for small fish in shadowy places, it uses fan-like fins to herd unwary quarry into a tight corner.
04:58Then, a lightning-fast gulp, and the prey disappears.
05:05Now and then, some small fish, like this baby puffer fish, seem to play with fire.
05:31Nipping at the fins of the lionfish.
05:38But puffers have a secret weapon.
05:41Snapped up by the lionfish, it swells into a prickly ball.
05:46The puffer is quickly spit out.
06:01This lionfish won't eat again until dusk.
06:06His slow-paced hunting style works best in dim light, when his prey can't see very well.
06:12But lionfish, and all reef creatures, ultimately depend on the reef's most intriguing and important animals.
06:20The corals themselves.
06:22Corals don't just live on the reef.
06:25They build it, inch by inch, laying down limestone that forms the canyons, terraces, and towers of an undersea metropolis.
06:33More than 500 species of coral form the Great Barrier Reef, and they grow in an incredible variety of shapes.
06:41Table-top and staghorn corals can extend their branches as much as six inches each year.
06:54Massive species like this brain coral may take a decade to reach the size of a baseball, but can live for centuries.
07:06Corals built this enormous three-dimensional labyrinth.
07:14Corals are considered animals, but they're not typical animals in any way.
07:21What we identify as a single coral is really a colony, each comprised of hundreds or thousands of tiny individuals called polyps.
07:33These polyp communities feed at night.
07:37Arms outstretched, they catch and strain food from water moving past them.
07:43But as the sun rises, polyps draw back into the protection of their limestone skeletons.
07:49For the rest of the day, these hard corals act less like animals than like plants.
07:58Protecting their delicate tissues from the jaws of enemies yet unseen,
08:02they spend the daylight hours capturing solar energy with the help of single-celled algae living in their tissues.
08:10The algae also enable their host to secrete the limestone that forms the structure of the reef.
08:23This intimate partnership helps make possible the incredible density of life here.
08:28There are some types of corals that manage to live without partners.
08:37Able to absorb nutrients directly from seawater, they thrive where hard corals would perish.
08:47Without the help of algae, these corals can't make limestone skeletons,
08:52so they don't add to the structure of the reef.
08:58Though they look fragile, they are actually tough and leathery.
09:10Just after sunrise, as coral polyps withdraw, all is quiet on the reef.
09:15For about 20 minutes, the reef is eerily deserted.
09:28The sun rises higher.
09:34Then suddenly, the reef swarms with life.
09:38Fish pour out of reef caves and crevices to feed through the daylight hours.
09:45Their eyes, finely tuned for sharp color vision, see as well or better than our own.
10:01Bright colors advertise their identity, sex, readiness to mate, and willingness to fight.
10:06There are hundreds of species, each of which has its own way of surviving on the reef.
10:19This tiny black and blue striped fish is called a cleaner wrasse, for obvious reasons.
10:24It spends its life cleaning other larger fish, searching for parasites, dead skin, and loose scales, all of which it eats.
10:37While doing this, the cleaner wrasse uses a small pair of fins beneath its gills to tickle the larger fish.
10:43Research shows that this tactile stimulation keeps clients coming back for more.
10:50Each cleaner wrasse has its own territory, called a cleaning station.
11:04Other fish learn where these stations are, and come calling.
11:15Including large predators.
11:19Groupers this size could easily swallow the cleaner fish whole, but they almost never do.
11:27In fact, when they open their mouths, it's usually to invite the wrasse inside.
11:33There, doctor becomes dentist, inspecting teeth, mouth, gills, and other tender spots that harbor annoying parasites.
11:41Even ill-tempered moray eels seem eager for the cleaner's attention.
11:55Morays are normally reclusive by day, preferring to keep most of their body hidden in a coral tunnel.
12:03At night, they hunt by smell and taste.
12:07Different species of moray range from a few inches in length to the size of a full-grown cow.
12:15Though they rarely attack divers unless provoked, their backward-pointing teeth make escaping from their bite difficult and painful.
12:26The morning rush hour is in full swing, as fish migrate between resting and feeding areas.
12:32These fish are plant-eaters, consuming algae that would otherwise carpet the reef surface.
12:40Food can be so scarce that this parrotfish tries to feed on the waste of others, recycling food that has been collected, but not quite digested.
12:52Some fish take time to get acquainted.
12:55Others are all business.
12:59This feisty damselfish is constantly fighting, mainly to defend its turf in the crowded reef metropolis.
13:06Staking out a claim on the reef surface, the damsel chases off all plant-eaters.
13:12Its territory is soon covered by a thick layer of algae, which shelters the tiny animals on which damsels actually feed.
13:23Damsels are quite aggressive for their size, willing to square off against intruders many times larger.
13:32They even chase off a full-grown surgeonfish, armed with razor-sharp spines, to protect the algae farm.
13:49The clownfish also fiercely guards its home, which happens to be the body of an animal called a sea anemone.
13:56This may be the most famous partnership on the reef.
14:00Anemone tentacles are armed with stinging cells that can be deadly to fish.
14:07But clownfish know instinctively how to protect themselves.
14:11From an early age, they rub against the anemone's body, mixing the host's mucus coat with their own.
14:17As a result, the anemone's tentacles treat the clownfish as part of itself, rather than as a separate animal to be stung.
14:28It's not only the clownfish that benefit from this association, finding shelter from fish-eating predators.
14:36But we now know the anemone gains as well.
14:39Like damselfish, these clownfish are willing to take on animals many times their size,
14:47and would not hesitate to attack if their host was threatened.
14:54But otherwise, clownfish never venture far from their anemone homes.
15:01As the sun rises higher, all is calm a few meters beneath the surface.
15:10But near the surface, waves batter the reef.
15:15The action of the water carves deep channels in the face of the reef.
15:23Beyond the breaking waves, the water is shallow and calm.
15:28As the tide ebbs, corals are exposed to air.
15:33Water rushes past them out to sea.
15:40These tidal currents, flowing across the reef, carry precious food in the form of plankton and a host of floating particles.
15:50Along the way, countless hungry mouths are waiting.
15:57What looks like a pair of feather dusters are actually the gills of worms, whose bodies are hidden within the reef.
16:03The plumes enable the worm to breathe and strain food particles from the water at the same time.
16:12Worms like these carpet many parts of the reef.
16:17Their gills vary in shape and color, but all serve the same essential purpose.
16:23Though these delicate structures may seem vulnerable to passing fish,
16:26they can withdraw in an instant if a shadow passes overhead.
16:38Everywhere on the reef, hungry arms comb through the water and unfurl to form living nets.
16:44Sea lilies, whose ancestors shared the earth with dinosaurs, perch in the current to snag their meals.
16:55They strain plankton and other food particles from the water with incredible efficiency.
17:00More than 80% of the plankton that washes onto a reef never makes it downstream.
17:16The great whale shark, one of the sea's largest inhabitants, feeds on some of the smallest.
17:22These filter feeding behemoths pump enough water through their gills every day to fill 5,000 swimming pools.
17:34Cruising with their mouths open, they strain enough plankton from the water to feed their massive bulk,
17:41which can reach 12 tons.
17:46The manta ray is another huge filter feeder.
17:49Though their wingspan can reach up to 7 meters, they too feed on tiny plankton.
18:00Twin scoops framing their mouth funnel water into bulging gullets.
18:13Solitary creatures, they remain on the fringe of the reef, rarely venturing inside.
18:20Meanwhile, on the hundreds of sandy coral islands that line the reef, the sun is high and the tide is low.
18:40Herons and other shorebirds eagerly stalk prey trapped in shallow tidal pools.
18:46A midday low tide can mean trouble here, for though hard corals thrive on solar energy when submerged,
18:55exposure to drying air and intense tropical sun can be deadly.
18:59Too much exposure kills corals, but many can survive brief periods by producing a thick layer of mucus,
19:10which later serves as yet another source of food for reef animals.
19:14High above the reef, frigate birds and gannets hunt for fish that they scoop from the water or steal from each other.
19:25Below wait their hungry chicks.
19:30Parents sit on their young, not to keep them warm, but to shelter them from the blazing sun.
19:41By hunting at sea and bringing food home, seabirds help fertilize the grasses and shrubs where they nest.
19:47Back under water, midday and low tide, things are quiet on the reef.
19:57Divers drop in for a visit.
20:02Their destination today is a small wreck claimed by the reef over a century ago.
20:19Over the years, floating and swimming larvae of corals, sponges and worms settled on every available hard surface.
20:36In time, they grew into a miniature reef.
20:39Its shape still testifies to human handiwork, but its carpet of life is now home to scores of reef species.
20:56It offers daytime shade to schools of fish and shelter to sea snakes.
21:09Sea turtles also find plenty of food here.
21:13Their powerful jaws make short work of even the toughest shells.
21:24Feeding slowly and methodically, they seem totally unconcerned about the divers.
21:39In the open water around the wreck, giant rays glide like birds in slow-motion flight.
21:42In the open water around the wreck, giant rays glide like birds in slow-motion flight.
21:43In the open water around the wreck, giant rays glide like birds in slow-motion flight.
21:53In the open water around the wreck, giant rays glide like birds in slow-motion flight.
21:56Back on the reef, swarms of plankton-feeding fish scour the water for food.
21:57In the open water around the wreck, giant rays glide like birds in slow-motion flight.
22:06Back on the reef, swarms of plankton-feeding fish scour the water for food.
22:11Back on the reef, swarms of plankton-feeding fish scour the water for food.
22:24Among the largest daytime fish are parrotfish, which often roam the reef in large schools.
22:45Using powerful beaks and jaws, they spend most of the day grazing on what looks like dead coral.
22:52They are after the algae that grow on and in this porous limestone.
22:59Every day, they process many times their body weight in coral rubble, keeping the reef surface free of excess algae and returning limestone as finely pulverized sand.
23:11The sandy rubble at the base of reefs looks barren to humans, but is a fertile feeding ground for reef fish.
23:26This wrasse leaves no stone unturned in its search for worms and other delicacies.
23:32Nearby, goat fish cruise hungrily.
23:37Their search for food is guided by pairs of chin barbels, which may look like whiskers but are covered with taste buds.
23:47They probe the sand, detecting buried prey.
23:52So successful are goat fish in finding food that they rarely hunt alone.
23:59Wherever they go, they are followed by freeloaders, eager to snatch any small animals scared up by the goat fish during their search.
24:08Less discriminating in its tastes, this sea cucumber inches along the bottom, swallowing a steady stream of sand and organic debris.
24:30Digesting what he can, he expels the rest.
24:33This whirlwind of activity is a school of marine catfish.
24:43Finding safety in numbers, they swarm along the sandy bottom in long, tumbling columns.
24:56Those in the middle are safest, but least likely to snag a meal.
25:01Those at the edge are more exposed and more successful in foraging.
25:12Other species shun crowds.
25:15These butterfly fish hunt as they live, in mated pairs, which stay together for life.
25:22Later in the afternoon, the shyest sand dwellers peer cautiously from their burrows.
25:34These are the elusive garden eels.
25:38Gathering in communities of up to 300, each digs a private meter-deep burrow with its tail.
25:44They use sharp eyesight to pluck food from the current, without leaving their burrows.
25:56If threatened, they can disappear in an instant.
25:59Where coral sand meets rubble lives the reef's true odd couple, the industrious blind shrimp and the watchful goby.
26:13The shrimp seems forever to be excavating the burrow they share, while keeping its long antennae in nearly constant contact with the goby.
26:27Like a guard dog, the goby eyes the surroundings for enemies, whose presence it signals with the flick of its tail.
26:37Other species of goby have more typical domestic arrangements.
26:55They live in mated pairs, share housekeeping chores, and stay together for life.
27:01As afternoon fades into early evening, lengthening shadows signal approaching danger for daytime fish.
27:18Plankton feeders become less bold and hug the reef more closely.
27:26The reason for their unease is soon obvious.
27:28As schools of predators gather and cruise along the reef.
27:38Among the first to appear are jacks and small barracuda.
27:47None of them are hunting, yet.
27:58They schooled tightly.
28:10Maintaining formation.
28:16Moving and turning together.
28:18Their prey also stick together.
28:32The eyes of many see more than the eyes of a few.
28:37This ability to school is due to a remarkable sixth sense located on the sides of their bodies.
28:44It enables them to detect and respond to minute vibrations made by the movements of fish nearby.
28:56While the maelstrom of flashing bodies confuses adversaries, members of the school can react instantly.
29:02As one.
29:14As twilight approaches, the reef takes on a heightened tension.
29:18Even large daytime fish gather together and move cautiously.
29:24Predators circle, ever bolder, ever closer.
29:34Sharks of several kinds rise from the deep.
29:51While others become more active.
29:53more active.
30:05The hunting begins.
30:06The hunting begins.
30:23Soon, another predator joins the fray.
30:42Using their own school to herd prey into corners,
30:46jacks dash through the panic throng.
30:54Ambush hunters like this small grouper benefit from the confusion.
31:00As prey are forced close to the reef by jacks,
31:04they become disoriented and easy targets for well-aimed jaws.
31:07Sensing danger from a distance, the flying gurnard spreads huge wing-like fins,
31:20making itself look as large as possible as it swims away.
31:25A razor wrasse dives for cover at the first hit of trouble.
31:28Lacking a true burrow, the flying gurnard spreads huge wing-like fins,
31:32making itself look as large as possible as it swims away.
31:46A razor wrasse dives for cover at the first hit of trouble.
31:50Lacking a true burrow, it knows where sand is soft.
32:02Even a harmless shrimp-eating shark provokes a hasty retreat.
32:10All over the reef, daytime fish stick closer to home
32:13and are ever more ready to duck for cover.
32:15As light dims further, their sharp daytime eyes no longer function well.
32:23They are at a disadvantage and they know it.
32:27That instinctive knowledge is vital.
32:30Fish who stray too far are eaten.
32:36Everyone seems to be heading for cover now.
32:40These shrimp fish usually seek shelter among the spines of sea urchins.
32:50But in a pinch, any vertical structure, like these sea whips, will do.
32:54The day shift is heading for home.
33:05But on a reef, commuting at rush hour is dangerous.
33:08The only law in effect here now is eat or be eaten,
33:23as twilight hunters stalk the reef.
33:26The only law in effect here now is eat or be eaten,
33:30as twilight hunters stalk the reef.
33:32In the air above the reef, seabirds return home.
33:33In the air above the reef, seabirds return home.
33:35To roost.
33:37To roost.
33:42In the air above the reef, seabirds return home.
33:49In the air above the reef, seabirds return home to roost and to preen.
34:19While below, despite the dangers, certain species prepare to risk their lives to mate.
34:39Groups of parrotfish gather and form trains along the reef.
34:43They aren't oblivious to the ever-present threat of cruising predators,
34:47but they risk their lives to give their eggs a chance to escape the daytime horde.
34:56Above the reef at sunset, damsels court in pairs and small groups,
35:02while parrotfish prepare for an evening of wild abandon.
35:08Milling about beneath the surface, they suddenly shoot upward, releasing clouds of eggs and sperm in unison.
35:15Chemical cues help the sperm find eggs in the swirling water.
35:26Below, on the reef itself, this clownfish family seems a model of decorum by contrast.
35:32The male guards the eggs, fanning them and keeping them free of debris.
35:41A clownfish nest can contain many thousands of eggs at once.
35:46And they are well cared for.
35:49But the sex lives of these animals are far from ordinary.
35:53The largest fish in the group is a female, who began life as a male.
35:59Like the consorts that surround her now, she, who was then a he, grew slowly, working his way up in the pecking order of the clan.
36:08When the reigning female died, male turned to female and began laying eggs.
36:14It's a somewhat unorthodox way of making sure that there will always be at least one male and female present,
36:21without requiring either to leave the safety of their anemone home.
36:25This female cuttlefish is just as fastidious about protecting her eggs.
36:38After placing them carefully, she guards them until they hatch.
36:56Shortly after, she will die.
37:03But the greatest drama of all is about to unfold.
37:18It is nightfall.
37:22The moon rises and exerts its own power over the creatures of the reef.
37:32A new crop of plankton fills the dark water.
37:37And coral polyps come out of hiding to act as animals and feed on the drifting plankton.
37:47Once active daytime fish settle down and sleep.
38:10This parrotfish has secreted a mucus cocoon that envelops its body.
38:16This fragile shroud may help mask its scent from predators who hunt using smell and taste.
38:23With the last daytime fish gone, the reef undergoes an amazing transformation as an unearthly crew of nighttime creatures crawls out of their shelters.
38:40What daylight exposes, darkness conceals.
38:45And what sunshine forbids, shadows allow.
38:49Daytime divers never see any of these fascinating animals.
38:57Some creatures, like the octopus, which are shy and secretive in daylight, become bold and adventuresome at night.
39:16Daytime diversifies
39:24Their patterned skin is filled with sacs called chromatophores that change color on command.
39:31They do this for camouflage.
39:33A remarkable feat given that these animals are thought to be completely color blind.
39:39The cuttlefish is also color blind and camouflaged.
39:59But it has sharp vision and quick reflexes which serve it well as a predator.
40:04Waves of color wash over its body in the excitement of the hunt.
40:25War of purple
40:44Elsewhere on the nighttime reef, harlequin shrimp manipulate their prey, a starfish.
40:51They drag it to their lair, immobilize it by turning it upside down.
41:21And spend the next several days devouring it alive from the tips of its arms towards the center.
41:32Banded coral shrimp, though active by day, are also out and about at night.
41:39They use claws and parts of their mouths to take over the job performed by cleaner wrasses
41:45during the day.
42:01Delicately feeding themselves, they also use their flexible limbs to keep their bodies free
42:06of debris.
42:14A host of other tiny animals, such as this transparent shrimp, have scarcely been identified
42:20because they hide so well and live in out-of-the-way places.
42:26This shrimp and its mate are found only in the gills of the giant sea slug called the
42:31Spanish Dancer.
42:34The largest of its kind, it is usually seen crawling along the reef after dark.
42:40But when disturbed, it swirls through the water, flapping the brightly colored mantle that gives
42:46it its name.
42:56Most of its relatives are smaller, but no less fascinating.
43:02They have dispensed with the protective shell carried by their terrestrial kin, the snails.
43:09Their gills are borne naked on their backs, hence the scientific name, nudibranch.
43:20In making shells, they seem defenseless, but that is hardly the case.
43:24In place of armor, they carry chemical weapons, usually compounds that taste foul, or poisonous,
43:31or both.
43:33Often they acquire and concentrate those poisons from sponges they eat.
43:39Their electric colors advertise their toxic cargo.
43:46Though rarely seen on the surface of the reef by day, they are common in reef caves and are
43:51out in the open at night.
44:01Their diversity of color and form is truly extraordinary.
44:09Some of them seem too bizarre to be real.
44:19The moon is just past full, and so is the tide.
44:25In the surf, a female sea turtle appears.
44:34She has returned to the very same beach where she hatched years ago.
44:40Driven by instincts older than the reef around her, she has come to lay her eggs, depositing
44:48them in a hole she digs in dry sand.
44:53Compared to floating in water, she breathes with difficulty, unaccustomed to supporting
44:58her full weight.
45:01The sex of her young will be determined by the temperature of the sand.
45:06At this time of year, most will be male.
45:20Having hidden her brood, she returns wearily to her watery home.
45:33As she swims out to sea, humans arrive to search the darkened reef for its nocturnal treasures.
45:49Her lights startle a few night wanderers.
46:02These divers, though they bide their time inspecting coral caves, have come to witness a once a year
46:08event.
46:14With the moon five days past full and the sea warm, the living reef prepares to reproduce
46:20itself.
46:22In the dead of night, polyps stop feeding and ready themselves to release eggs and sperm.
46:29first, one at a time, then in greater and greater numbers.
46:54Corals across the reef join in a silent frenzy of mass reproduction.
47:05Some polyps cast only sperm into the tropical night.
47:13others produce only eggs.
47:23Others produce only eggs.
47:34Some spew forth eggs and sperm at once.
47:45In the water, these fuse to produce larvae that eventually become coral polyps.
47:53Some coral species release larvae that have been fertilized inside polyps and are now ready to
48:12swim off on their own.
48:14However they are produced, the larvae of some species will settle within days and begin new colonies
48:21quite close to their parents.
48:25Other larvae may swim and drift for months in waves and currents, possibly even founding new
48:32reefs far from home.
48:37How, when, and why do coral larvae decide to settle?
48:43We still don't know.
48:45As corals spawn, other animals join in.
48:49Sea cucumbers sway in ponderous slow motion dances, while nudie branks play their own game.
49:02These animals are both male and female at the same time, and act that way.
49:08Each place female to a mate behind, and male to the one in front.
49:15And then, sometimes, they switch positions.
49:22All around the water is filled with coral spawn.
49:26Sperm follow scent trails to eggs of their own species.
49:31Plankton worms release long sections of their bodies that are filled with their eggs and
49:36sperm.
49:50With luck, currants will carry these clouds far from the reef before the swarms of plankton-feeding
49:57fish awake after dawn and eat them.
50:04This is how reefs build and expand.
50:07This is how new reefs get started.
50:10But it is still a struggle to survive.
50:21By the light of the next day, hungry fish swarm to feast on a rare treat, a giant slick of
50:29congealed coral eggs and sperm.
50:32The vast majority of the spawn will not survive.
50:53Still, such enormous quantities have been produced that enough survive to perpetuate the life of
51:00the reef.
51:10Meanwhile back on the beach, hatchling turtles from an earlier clutch dig out from their sandy
51:16nest and scramble madly for the sea.
51:25The time they emerge is determined by the temperature of the sand.
51:30Sometimes it's during the day.
51:32But usually they emerge under cover of darkness to protect them from enemies that stalk them everywhere.
51:38The first moments of their journey are the most perilous, as they run a gauntlet of hungry mouths.
51:55Only because of their numbers do any reach the relative safety of the surf.
52:03And the reef holds its own dangers.
52:19The water's surface by day is no place for young turtles.
52:30Of the few that escape to open water, some will grow to a safe size and will return some
52:36day to call the reef home.
52:41Much of their life remains a mystery, like the drifting coral spawn.
52:47On their survival, the future of the reef depends, and the continuation of a community like no
52:55other in this world.
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53:15THE END
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