Original subtitles

(perky music)

These images, taken less than five years ago,

were the first ever recorded of that almost mythical

inhabitant of the deep sea, the giant squid.

Its body is over twice the height of a man,

its tentacles, four times that length.

No one before had seen it alive in its natural habitat.

Filming it was a historic triumph.

Now the scientists and cameramen who captured

these amazing pictures, have teamed up once again

to explore still further the least known part of our planet.

They're armed with the latest in deep sea technology,

and a new, highly sensitive camera,

that can record pictures in near total darkness.

The team is heading for a deep sea gorge

off the coast of California, and this time

they hope to reveal another of the ocean's astonishments,

(charming music) (chimes ringing)

creatures that glow in the deep.

It's so rich, it's so bright,

so thick, so dense, it's so many

different kinds of luminous displays.

And with them, the bizarre animals

that prey on them.

This is a journey to the Earth's darkest frontier,

(cheerfully busy music)

to try and unravel some of the secrets

of these extraordinary living lights.

On the west coast of California, 200 kilometers

south of San Francisco, lies Monterey Bay,

world famous for the richness of its marine life.

Cold Pacific currents bring an abundance

of nutrients into the bay, which support

great numbers of sea mammals.

Whales.

Seals.

And drifting among the floating kelp, sea otters,

floating leisurely on their backs,

cracking open shellfish on their stomachs.

(cheerful music)

Beneath the surface of the sea,

lies the largest underwater canyon

off the coast of North America, over 3000 meters deep,

and rivaling in size the Grand Canyon.

The jagged walls of the Monterey Canyon

drop down steeply and create a unique underwater landscape.

The cold, sheltered waters provide a home

for many deep sea animals, and new species

are still continually being discovered.

Between 200 and a thousand meters deep,

light gradually diminishes into blackness.

This is the twilight zone, where little sunlight penetrates.

Many of the creatures that live here

produce their own light.

The expedition plans to dive down into this zone,

guided by Dr. Bruce Robison, who's worked

in Monterey bay for many years,

and is a world expert on deep sea animals.

We have been studying this place for 25 years.

And yet we still find new animals.

It is like treasure hunting, uh,

and you never know the nature of the treasure.

Robison himself has made many discoveries

in Monterey Bay over the years, but he knows well

that exploration here has only just begun,

and all kinds of astonishments may await.

Now the team will deploy his specially designed

research submersible for their first exploratory dive.

(water bubbling)

It's un-manned, but it carries a camera

that sends pictures to the surface by a cable.

Here we go.

(amusingly inspiring music)

A pair of inquisitive seals

come to check out the strange machine.

It slowly descends into deeper waters.

200 meters.

Now, it's entered the twilight zone.

So little light from the surface reaches these depths,

that to our eyes it's virtually pitch black.

It's time to turn on the sub's lights.

(pleasant music)

What is that?

It's a strange, ribbon-like worm.

We call 'em wiggle worms, and they are,

they are really fun to watch because

they go through all of these contortions

and they make spirals, and circles, and loops.

Well that's, they seem never to tie themselves

into a knot that they can't get out of.

And then, another strange creature.

Oh it's a salp.

Oh.

The salp is in fact not one individual,

but a chain of nearly 50 linked together.

Sea salps are jelly-like filter feeders

that suck water in through their tubular mouths,

and filter out tiny food particles.

(eerie tense music)

Something likes to--

DJ let's stop on that!

Robison has spotted something else

in the darkness.

It's a kind of comb jelly called Beroe.

(suspenseful music)

Rows of tiny beating hairs run

the entire length of its body.

It's a magical sight, but it's not bioluminescence.

The shimmer is merely reflected from the light

coming from the submersible.

A small squid appears in the headlights.

It hangs in the water, waiting for prey

to get caught on its long tentacles.

(brooding music) And it has a remarkably

large eye for such a small animal.

Many creatures here have huge eyes.

They need to be able to follow prey,

or pick out the shape of a predator in the near-darkness,

and there are plenty of those around.

(tense music)

In the open ocean, there is no place to hide.

The submersible is now halfway into the twilight zone.

600 meters.

They're hoping to see one

still little known creature that lives

at this particular depth.

(suspenseful music)

And here it is.

A fish called the barreleye.

Its extraordinary head, is encased in

a transparent dome so that you can look right inside.

Its eyes within their transparent shield,

are enormous and point upwards.

Robison first encountered this bizarre animal

over a decade ago.

At this point we were very, very excited,

because no one had ever seen one of these alive, before,

only specimens that had been caught in nets.

And as we watched it, we realized

that it looked very different than all

the specimens that had been collected by nets.

This, transparent dome, over the eyes,

had never been seen before.

When you catch these in the nets, that's all scraped off.

It was an extraordinary discovery,

and the strange fish with the see-through head

would make the headlines.

While the transparent shield was thought to

protect the eyes, it was a puzzle as to how the fish

could catch prey with its forward-facing mouth

if it can't see what it's feeding on.

It was a mystery that Robison would

also solve some years later.

(serene music)

Many of the creatures in the deep,

like the barreleye fish, defy imagination.

And here's another, the Black Sea Devil.

It's a kind of angler fish, with a bony rod

and a luminous lure hanging from it

perched on the top of its head.

Every dive down to these depths brings new discoveries.

Look at the black fish, oh! Go, where?

Oh, right there!

Ooh!

Ooh.

It's an excellent Dragon.

See-- Ooh!

It's a deep sea dragonfish.

I thought that was-- It's makes red luminescence.

Oh really? Yeah yeah!

The red spot just below the eye

is a photophore, a light emitting organ.

Even Robison has never seen it in action before.

Looks better to me.

Good lets do it.

The sub has a special suction device

with which they might catch it.

(groaning)

But it's not easy.

(mumbling)

Robison wants to bring it to the surface,

so that he can study it closely.

Oh right in there! Oh you got it, got it!

All right! (mumbles) all right.

Now he'll have to act quickly.

With the enormous pressure change,

the fish may not be able to produce its light for long.

The deep sea dragon is only 10 centimeters in length,

but Robison is keen to find out how its

light producing organ works.

I think it's enough water in there,

unless you feel like you want more.

No. Okay.

(mumbling)

To see the photophore in action,

they'll need some highly specialized equipment.

(patient music)

The red light emitted by the photophore

is too weak to register on an ordinary camera,

but the team has developed one that is

600 times more sensitive.

Tested outside on a clear night,

it produces an astonishingly sharp image of the stars,

so it should be able to detect the light

produced by bioluminescent animals.

The team have set up a filming tank

in a dark room with water that's

kept at the same temperature as the deep ocean.

With any luck, the dragonfish should behave

relatively naturally in these conditions.

Under normal lights, the fascinating creature

lives up to its name.

It looks truly fearsome.

And the two photophores are clearly visible under each eye.

But in the dark, the photophores light up.

They glow in unison, one red and the other blue.

And then, a surprise.

(dramatic music) Whoo!

(mysterious music)

This is something that no one has ever seen before.

That's unexpected, and it's interesting.

Ooh!

It's a spectacular display.

But what is its function?

It could be to frighten off a predator,

but no one knows.

We may not find the answer for many years yet.

Bioluminescence isn't limited to the ocean.

It's found in creatures on land, even in the air.

Fireflies flash their lights to attract a mate.

Some woodland fungi glow bright green,

attracting insects, maybe to distribute their spores.

And at certain times of the year,

beetle larvae emerge from termite mounds

and illuminate them like Christmas trees.

But in the deep ocean, 90% of the creatures produce light,

and we still know very little about why they do so.

The only way to find them in the pitch black

is to shine our own lights on them.

But when we do that, it's impossible to see

the much weaker living lights that the

animals themselves produce.

So studying the phenomenon is extremely difficult.

The mysteries are how they use it,

what are they saying to each other with that light?

The problem was that we never had a camera that we could

take down and use to record bioluminescence,

and that's why it was so important for me

to go down and see it with my own eyes.

Now Robison and his team

have an opportunity to use the latest technology

to tackle the problem.

They'll be working from the Alucia,

the same research vessel that helped

the film team find the giant squid.

(voices drowned out by ship noise)

Hi I'm Taylor.

Mark, pleased to meet you.

I've heard about you--

The high-sensitivity camera system

that took two years to develop will now be really tested.

The crew carry out last minute checks

on the submersible before its dive

into the Monterey submarine canyon.

At the kind of depths at which they'll be operating,

every precaution has to be taken.

The camera is carefully installed on a mount

attached to the outside of the submersible.

At last everything is in place and they're ready to go.

(machines humming)

I'm excited like a boy, I,

I now I'm gonna have a lot of fun.

Robison has spent a good part

of his career exploring the ocean depths,

but he still gets excited before each dive.

Welcome! Hi!

Thank you (laughs)!

After his submersible, the Nadir,

has been lowered into the water,

a second sub, the Deep Rover, is also launched.

(chattering)

Do I copy?

Yes.

Good. Okay, here we go.

(water bubbling) (water splashing)

We're flooded.

And the dive begins.

Their aim is to descend to a depth of 600 meters

into the middle of the twilight zone.

(mumbling)

Soon the light levels start to fall,

and they enter a dark, blue world.

(eerie suspenseful music)

Control control, the Nadir's

at 200 meters, descending over.

Something off the front.

Yeah, there's quite a long one there, isn't it?

Yes.

This may look like a piece of string,

but in fact it's a huge colony

of living creatures linked together.

They're called siphonophores,

and are relatives of the jellyfish.

Siphonophores are very unusual creatures.

They are a colony of individuals

all connected to one another.

We have found individuals that were 40 meters long,

longer than a blue whale, the longest creature on Earth.

The individuals of the front contract

and expel water simultaneously,

so slowly moving the colony forward by jet propulsion.

The rest of the chain extend hair-like tentacles

to catch passing prey.

There may be hundreds, if not thousands

of individuals in a single chain.

Each one performs a particular function

and occupies a particular place within the colony,

much like the organs in our bodies.

This super-colony works as a team.

But how individuals communicate with each other,

and coordinate their movements is still a mystery.

Ooh, there's Colobonema.

Very, very pretty medusa.

Colobonema is a small jellyfish

just five centimeters long,

but it's a strong swimmer, and as the sub

gets closer, it puts on a turn of speed.

See, he just dropped his tentacles.

Oh!

(machine whirring) Cool, you got it!

The small jelly sheds his tentacles on purpose.

It's a ploy to confuse predators.

While our eyes follow the discarded appendages,

Colobonema makes its escape.

Control control, Nadir passing

570 meters, descending over.

The sub is nearing the 600 meter mark.

Oop, stop Andy! Over.

See that-- Yeah, yeah.

(mechanical whirring)

Go slowly.

That's an owlfish.

It seems to be scared

of the subs bright lights.

(mechanical whirring)

(clicking)

So the crew decide to switch them off.

They turn on a much weaker light,

adjust the sensitivity of the camera,

and the fish comes into view again.

Wow. Nice.

Wow!

Like many deep sea creatures,

the owlfish has huge eyes, which can detect

the faintest trace of light,

including the living light of its prey.

The fish uses the very minimum of energy,

and simply hangs in the water, waiting for prey to swim by.

Having a camera with this sensitivity is

very exciting, because of the things it may reveal,

things that we don't even know are here,

that may appear for the first time.

Again, because we can work with very low light.

Aww!

Oh and here's a, here's...

It's the Beroe comb jelly again.

In the submersible's headlights,

it shimmers with refracted colors.

But what would it look like if the lights were off?

Sure.

(clicking)

(eerie music)

In the dark, Beroe produces

the most astonishing intricate pattern of light,

all along its body.

This is bioluminescence.

Ooh, look at that!

Ew! This here!

Yeah! That's a big one.

Holy cow!

What a beauty!

The striking red torpedo is

a Periphylla jellyfish.

It's a voracious hunter that uses stiff tentacles

to catch its prey.

(tense music)

But it also has another trick up its sleeve.

That's a very luminescent animal,

when it is stimulated.

Okay.

So as not to scare it,

they switch to a red light, which the jelly can't detect.

(eerie serene music)

(chimes ringing)

And then it starts a totally different performance.

It starts to eject the tiny blue particles.

They drift away, leaving a trail of twinkling blue lights.

What is going on?

No, stay away, stay away,

stay away, stay away!

Aah!

The crew try to keep away from the jelly

but the currents created by

the submersible have disturbed it.

It's response is to eject its living lights.

(eerie tense music)

It seems that if threatened, Periphylla tries

to trick a predator into following the glowing trail,

and so enable the jelly itself to escape.

Ooh, there's a Tomopterid worm.

Yes.

The transparent worm

seems to crawl through the water with its bristly legs.

(chimes ringing) But when disturbed

it also ejects glowing lights.

(eerie tense music) (chimes ringing)

Many other bioluminescent creatures make an appearance,

and the crew are able to capture

their displays with the new camera.

Living in this twilight zone depth, right,

which is very challenging for the animals

that choose to live here, because there are no

rocks or trees or holes in the ground

where animals can hide.

It's a truly three-dimensional space without

boundaries or borders. (chimes ringing)

Light is an extremely

important way that the animals deal

with the challenges of living here.

(eerie tense music) (chimes ringing)

The team have been underwater

for nearly eight hours.

It's time to come up to the surface.

(water bubbling)

(water splashing) (water bubbling)

It's two days into the expedition

and they're awaiting the arrival of a visitor.

Dr. Edith Widder is a world expert on bioluminescence.

Don't step on that! Yep, thank you!

Well done, how are you? Good.

She's worked with Robison

many times over the years.

Oh you believe this?

Yes.

Anyway, Yeah!

oh, I'm glad you're here.

(laughs) I'm glad you-- I need all the help

I can get! Oh yeah (laughs)?

Widder was part of

the giant squid expedition in 2012.

She had developed an electric jellyfish

that emitted flashing lights similar

to that used by deep sea creatures.

That had helped the team to attract

a giant squid so that they could film it

alive for the very first time.

(astonished gasping)

Now Widder has brought along some new gadgets

that she's developed specially for this expedition.

This is one of them.

She calls it a a Splat Screen.

If deep sea creatures unknowingly swim into it,

she thinks they'll produce bioluminescence,

and their special camera should then be able to film it.

Oh I think it's gonna be an incredible dive.

I can't wait to try out the new Splat Screen,

and so, to be able to see now

what this camera's gonna be able to see,

because in those early days I didn't know

what I was seeing, and over time I've gotten

so I can identify a lot of the animals

by the types of flashes they produce.

But I thank that's gonna be even easier to do

now with this camera system.

Widder will work from

the second submersible, the Deep Rover.

And Robison gets ready to head down in the Nadir again.

On this dive they're planning to descend

right to the ocean floor.

Control Rover, my depth, 770 meters,

on bottom, over.

After an hour, they have made it.

(mysterious music)

The sea floor is thronged with fish.

Nutrients falling to the bottom,

and accumulating there, attract a great variety of animals.

This, small little sea pen, you see it?

Yeah that's, oh that's a ri-my-a.

(tense music)

Sea pens are (mumbles) creatures

that anchor themselves to the sea floor.

They prefer deep waters, where they're

less likely to be uprooted by ocean currents.

(mechanical whining)

But they're not safe from

the robotic arm of the submersible.

(chimes ringing)

And when touched, the glow.

(eerie music) (chimes ringing)

This is a different kind of sea pen.

It produces a blue, pulsating light.

(chimes ringing)

Widder is keen to try out the new Splat Screen

to see if that will stimulate animals

to glow that they might otherwise miss.

All right, are you ready for the screen?

Yep.

(mechanical whirring)

Okay, all lights off.

All lights off.

(clicking)

(suspenseful music)

As their eyes adjust to the darkness,

they see the first faint glow.

It's a jellyfish, and as it comes closer

Widder is able to identify it.

That's a (mumbles) jelly.

I think that's Atolla.

Yeah it is, it's Atolla.

And the ultra-sensitive camera

is able to record its complex light display.

(eerie music) (chimes ringing)

As it touches the screen, it produces

a spectacular strobing of blue light.

Widder suspects that the function of this display

isn't to scare off the enemy,

it may convey another message.

Now she brings her electric jellyfish into action.

(water bubbling)

It's programmed to emit the same pattern of light as Atolla.

(energetic orchestra music)

A low light camera reveals that the blue flashes

quickly attract large fish.

And a gigantic deep sea predator.

A Pacific sleeper shark, nearly three meters long.

It's not a threat to the jelly,

it seems to be preying on the smaller fish,

that are in fact the jelly's real enemies.

So the jelly's flashing lights may be acting

as a call for help, a kind of living burglar alarm.

It has this remarkable ability to produce

this pinwheel of light, and so clearly,

if it was a scream for help, then you would think

that that pattern should be

very attractive to large predators.

It's an intriguing idea.

In the meantime, Bruce Robison is in the Nadir

and making his own discoveries.

Rover Nadir, over. Ooh, stop Andy.

Over. See that--

Yeah, yeah. (mechanical whirring)

This is a viper fish, a fearsome predator,

and it too creates light.

You see those spots along his belly,

Oh yeah. those are

bioluminescence organs.

Oh yeah.

Rows of small photophores run along

the length of its underbelly, and produce blue light.

(eerie tense music)

From below, the fish lights up like an airport runway.

Interestingly, many deep sea creatures

generate light on their undersides.

Why should this be so?

It seems that the lights may actually help

to camouflage the animals from

predators lurking beneath them.

One creature that uses its lights to this effect

is the firefly squid.

(cheerfully busy music)

Hundreds of tiny photophores illuminate their bodies.

Why don't these bright lights attract predators?

A small amount of light from the surface

filters down into the twilight zone,

so from below, a black silhouette would be clearly visible,

and make an easy target for deep sea hunters.

A predator from down below, looking for a meal,

might see the body of an animal silhouetted

against the lighted waters above,

and would use that silhouette as a guide

to strike and feed on.

But the squid's lights prevent that

by breaking up its silhouette.

Through a thick layer of water this effect

is even more pronounced.

And by controlling the intensity of its own light,

to match the background, the animal blends

into its surroundings.

So contradictory though it may sound,

light in fact conceals.

Many animals who live in this part of the ocean

eliminate that threat by producing light

along their bellies and erasing their shadow

so that they cannot be seen.

But there is one predator

that's not deceived by this trick, the barreleye.

It has evolved its own special hunting technique.

It hangs almost motionless in the water,

with its large eyes directed upwards,

searching for the faint silhouettes of prey overhead.

The eyes are green, because they contain

a pigment that screens out bioluminescence

that other animals use to hide with.

So it's not fooled by the counter-illumination

of that bioluminescence.

Although no one has ever seen how

the barreleye hunts, Robison has studied the animal

closely, and come up with a theory.

It feeds on small krill and other plankton.

Some prey try to hide by using bioluminescence.

But seen through the eyes of the barreleye,

the deception does not work.

The hunter can clearly see its prey.

(suspenseful music)

The barreleye approaches stealthily from below,

and as it rises to the level of its prey,

it rotates it's eyes.

(dramatic music)

Eternal darkness has caused creatures that live here

to evolve all kinds of shapes and strategies

that are utterly different from those we use ourselves,

and one of the key elements is the ability to create light.

(brooding music)

(chimes ringing)

They just seem strange to us,

because we are so accustomed

to living in a very different world.

Some are virtually blind,

and rely on other senses to catch their food.

While others have particularly large eyes that

enable them to see in the dimmest of light.

They've all evolved their own ways

of dealing with the darkness,

but most of them us bioluminescence in some way or other.

So perhaps it's not surprising,

that nature's greatest light show

happens in the one place where there is continuous darkness.

(serene music)

Control control Rover,

passing 300 meters, descending (mumbles).

Deep Rover is slowly heading upwards,

with the splat screen still extended.

It lights up with the glow of small creatures

that come into contact with the net.

By freezing the image from the camera,

it's possible to identify some of the animals

that are creating the light.

These are copepods, small crustaceans

just a few millimeters long.

When threatened, they can discharge a bioluminescent liquid.

They're one of the most abundant creatures in the ocean,

and the main source of food for many fish.

(relaxing music)

These small creatures may provide a clue

to understanding why bioluminescence is so

widespread in the deep ocean.

It's long been a mystery as to how

deep sea animals produce light,

but science is now beginning to find some of the answers.

Most deep sea animals produce bioluminescence

with a molecule called coelenterazine.

When this reacts with certain enzymes in their bodies,

it produces light.

So bioluminescence may seem like magic,

but in fact is the result of a

straight-forward chemical reaction.

But there is nonetheless, one mystery.

Most deep sea animals themselves

can not produce this light emitting substance,

so where does it come from?

A Japanese researcher, Yuichi Oba,

may have found the answer.

Oba has been studying deep sea copepods,

and he's discovered that one particular species

is able to make coelenterazine within its body.

It's called Metridia pacifica.

We still don't know how many others can do the same,

but it's a clue as to where the luminous molecule

could have come from.

But how is it that the same molecule is also found

in many other deep sea creatures?

Well, it appears that it spread through the food chain.

Copepods are the main source of food

for many shrimps and small fish,

so the coelenterazine molecule will be

transferred into the bodies of their predators.

The shrimp in turn may pass on

the molecule to their predators,

squid and larger fish, which in turn

are eaten by even larger hunters.

So the light emitting molecule could have spread

from prey to predator and so through the whole

community of deep sea animals.

It's an extraordinary thought,

that the living light produced by some of

the smallest creatures in the sea, could be the basis for

the incredible light shows in the ocean.

The precise function of bioluminescence may vary.

Some use it to intimidate their enemies.

Others to hide from predators or to call for help.

But the meaning of many of their messages

still remains a mystery.

(serene music)

As the expedition draws to a close,

the team prepare for one last dive to watch

a particularly spectacular event.

It happens every night as the sun drops below the horizon.

It's a time when vast numbers of deep sea creatures

rise towards the surface.

The team are hoping to film the spectacle

and the light show that goes with it,

and to do that properly they will deploy both submersibles.

When we get up to 200 meters or maybe 100,

we should coordinate and if there is a thick layer

of luminescence, we should try

to shoot each other as we drive through it.

The submersibles are launched

while there's still light.

(water splashing)

As they descend deeper, and night falls,

they once more enter the world of darkness.

And it's not long before they're

traveling through a large swarm of krill.

Not bad, just going up.

The small crustaceans are on

their daily migration up to the surface,

where they will feed on plankton.

Others have also been hiding in deep waters

to avoid predators.

Now there's a mass migration of animals up

towards the surface, where food is more abundant.

But this vast migration attracts some bigger hunters.

It's an electric torpedo ray.

They usually live down near the bottom,

but at night it comes up to feed.

It's 5:30 p.m., and the sun has set.

The submersibles are in position.

Control control, the Nadia's at 200 meters

with Rover, over.

The submersibles are hanging motionless

at a depth of 200 meters, but to really see

what they've come for, they need to turn off all the lights.

Let's give it a try.

(clicking)

(tense music)

The first glowing lights appear,

and the show begins.

(serene music)

With every passing minute, the firework display gets bigger.

The subs are now surrounded by light on all sides.

Ooh, ooh! Yeah!

Aw! Oh yeah!

Pretty good, pretty good.

Yeah.

Wave after wave of living lights

well up from the deep.

So, copepods, and krill, there's na-nomia,

there's a suggestive (mumbles).

Millions of glowing marine creatures

continue to appear, and amongst them could well be

other strange life forms that we've not yet encountered.

The underwater night sky is now illuminated

by hundreds of shooting stars.

The show continues for over two hours,

and when they come back up to the surface,

the scientists are ecstatic.

Look at that! Yeah!

It is the Milky Way!

But it's also scientifically very interesting

that you can actually see the different colors.

But scientists have yet to discover

the meaning of many of these living lights,

and how and why they are produced.

Most of the animals in this vast, vast volume make light,

and that much of it we still don't understand

what it's used for.

That's a huge mystery.

We have only begun to explore.

And, we continue to find new discoveries

every time we go into the ocean, so yes,

we've only begun to find out what's down there,

to learn how these pieces of a gigantic puzzle

fit together and work as an ecosystem.

Yes, we're just getting started.

(cheerful music)

The deep oceans and their mysterious

light producing creatures have long been out of our reach.

Now, with the help of new technology

and the latest research, we're beginning

to unravel some of their secrets.

But many mysteries remain, and we're still

a long way off from understanding just what makes these

marvelous living lights glow in the abyss.

(cheerful busy music)