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[gentle music playing]

[narrator] Welcome to Australia.

We're currently in the northeast of the Australian continent,

and beneath us lies the Great Barrier Reef.

The magnificent, clear water stretches as far as the eye can see.

Beneath the surface lie the coral reefs

that have spread across the entire area,

huge structures already visible from the air.

A truly exhilarating view.

What we can't see from up here is an astonishing variety of life forms,

waiting for us in the reef's depths.

They are the reason for our visit to this marvel of nature.

[gentle music continues]

The Great Barrier Reef is the largest coral reef on the globe.

It lies by the east coast of Queensland State

at a length of about 2300 kilometers.

The total area covered by the reef

spans a stunning 350,000 square kilometers.

It's home to an incredible abundance of life.

2600 types of fish, 600 types of corals,

and clams up to 120 years of age are among its inhabitants.

Since 1981, the Great Barrier Reef

is part of the UNESCO World Heritage.

We meet with a true veteran of the Great Barrier Reef,

a man whose life is deeply connected with the reef now

for over 40 years, the American-born John Rumney.

In 1974,

I came here to Australia

to experience the Great Barrier Reef.

I didn't really know.

I'd read about it in National Geographic and books.

And, came up the coast

and in fact went out of Cairns to Green Island,

and that was the only tourism.

There was no-- Everything you see today,

the $6 billion industry, 60,000 people.

None of that existed.

It was just a few fishing boats

and this one ferry that used to go to Green Island.

Got there, jumped off and it was amazing, mind blowing.

The dance of life,

the next hour that you're in the water,

you will see more animals than you will the rest of your life.

I had done snorkeling when I was like, 11 or 12,

for the first time, and I think that was my change of life.

Because it went from being--

Just generally loving animals, snakes, lizards, crocodiles, things like that,

and once you were in the water, then it was 3D.

It was, you know, in your face

and so much more, being in nature, in a forest or in the mountains.

When you jump in like a Barrier Reef coral reef,

it's just hundreds of things and thousands of them.

[gentle music playing]

[narrator] Once we start diving below the surface,

we have to agree with John Rumney.

It's overwhelming just how colorful, alive,

and densely populated the reef happens to be.

Among the fish we see gigantic swarms.

On one hand, there are larger groups of fish

that roam the reef together.

On the other hand, we find dozens of tiny, colorful fish

that stay close to their corals along with other fellows of their kind.

This way, they can quickly hide inside the branching structures

when danger is nearby.

Of course, the corals themselves are a feast for the eyes.

With over 500 different species that inhabit the reef,

the corals impress with countless forms and stunning colors.

[gentle music continues]

After all these impressions,

it's evident just why John Rumney made the decision

to stay in Australia.

He started out in the fishing industry

and later went on working in tourism.

During this time,

he made use of every opportunity to snorkel

and enjoy the enchanting act that presented itself underwater.

This way, he experienced the spread of tourism first-hand.

In present day,

it's an industry that employs over 60,000 people

at the Great Barrier Reef alone,

and makes annual sales in the billions.

But with time, Rumney noticed transformation in the reef.

Throughout the years, a grave problem began to appear

that now turned into a threat

to the rich diversity of species in the Great Barrier Reef.

A growing number of the corals are dying.

It's been an evolution.

Ah, coming here and first seeing the reef

in an incredibly vital, vibrant, pristine condition

and now, over the years, it's just decreased over time.

And, with this last bleaching event of 2016,

it's been like, it's so emotional.

It's completely changed and you went,

"Wow, this was a global warning."

This is the canary in the coal mine.

This is the turning point for me that we know

we must really act now or we will lose the Barrier Reef.

We won't lose all the coral in the world, no.

But we might go into the dark ages of coral, right?

It won't be what we see today.

We won't have the fish, we'll lose the biodiversity.

We'll even possibly lose our food security.

We are, out of our ignorance and lack of commitment,

really tampering with the basic physics of the ocean.

And that could be catastrophic.

[gentle music playing]

[narrator] The bleaching event that John Rumney refers to

bears this name for a reason.

Actually, the term is quite fitting.

A major part of the reef consists of limestone,

naturally of white color.

It formed from coral excretions

and functions similar to a skeleton.

The corals receive their varying colors

from a symbiotic relationship with different types of algae,

a relationship of mutual partnership.

The algae supply the corals with oxygen and energy.

But these algae are very sensitive when it comes to their environment.

A change in the water's chemistry or just a change in temperature

can cause a devastating chain reaction that kills off the symbiotic algae

and thereby results in the death of the corals.

This way, the bleaching event of 2016

caused a vast number of algae and corals to die off,

leaving nothing but blank, white limestone.

This became the term's infamous origin.

The event left nothing but a spooky wasteland.

It's even more frightening

when one knows of the abundance of life

that populated this place just recently.

With this in mind, the dead corals appear

just like a large pile of carcasses,

almost resembling a Dunning graveyard.

However, this hasn't been the first time.

Between 1985 and 2012,

the total coral covering of 28%

shrunk by more than half of that amount

to an alarming 13.8%.

Further drops ranging from five to 10 percent

over the next 10 years are thought to be inevitable,

caused by humanity's emission of carbon dioxide.

[somber music playing]

Well, I think that the Barrier Reef is the first symbol,

the first visible example of what is coming.

Like, yes, the corals are sensitive to temperature.

So, we've had a definite temperature rise

due to the CO2 emissions.

With this coral bleaching,

we're having this definite affect on the reef health

and many of the corals are dying,

so the next event, more will die and more will die.

So, this is a process of deterioration.

What we will lose, is the biodiversity.

The most different species in a given area

are right here on Barrier Reefs.

You know, thousands of times more animals per 100 meters

than in other parts of the ocean.

[gentle music playing]

[narrator] That very variety that Rumney speaks of

and that we witness around us,

is what makes the Great Barrier Reef so unique.

[upbeat music]

But where does this variety come from in the first place?

First and foremost, it's the work of the corals themselves.

The main actors in our globe's reefs

are the stone and fire coral.

Over the course of many millennia,

these living beings created giant formations

and even entire islands.

Among those are the Bahamas, Bermuda, and the Maldives,

but none of these are larger than the Great Barrier Reef.

[upbeat music continues]

Corals even compete with us humans

as the constructors of the largest connected structures on our planet.

Corals, being part of the group Cnidaria ,

achieve this by constantly releasing limestone.

The symbiodinium, a microorganism

that lives in a symbiotic relationship with the coral,

helps with the calcification and supply.

The symbiodinium supplies the coral with hydrogen,

and when it comes to the water's temperature,

they are very sensitive.

It always has to remain between 20 and 30 degrees Celsius,

which is why they're mostly found in flat, tropical,

and light-flooded waters.

Stone and fire corals

are nothing but gigantic colonies of single polyps.

Every single polyp is only about one centimeter in size.

Despite the food supplied by their symbiotic partners,

their diet consists mostly of plankton organisms

that they catch using their tentacles.

[upbeat music continues]

Fire corals are named after their stinging cells,

which they can use to break through the human skin

and inject a painful poison.

The symptoms are similar to those of touching poison ivy,

where the pain can last from two days up to two weeks.

The injuries can even lead to scars

that sometimes remain visible for a lifetime.

Divers should be especially careful

not to make the common mistake of confusing a fire coral with seaweeds.

[calm music playing]

In order to protect themselves

and fight for their space in the reef,

corals make use of so called defense polyps

that are larger than the normal ones.

They can use them to inject a poison

into the opponent's tissue, thereby destroying it entirely.

When it comes to the spreading among sessile species,

the ones that are unable to move about,

fire corals are very successful.

In the battle for light and space,

they can overgrow their rival very effectively,

as they grow relatively fast.

But they are unable to do so

without a symbiotic relationship with the symbiodinium,

and that very species is in grave danger of going extinct.

The bleaching event of 2016 didn't just startle John Rumney.

The Barrier Reef is the first symbol or the first sign.

It's the fever, "Oh we'd better go to the doctor,"

"Oh look, looks like you might have cancer."

"Ah, well, what's the treatment?"

"Well, stop smoking or," you know, whatever it is

that you need to adjust and take some remedies.

In our case, our remedy is: pull CO2 back out of the air.

Stop polluting and pull it back,

get the temperature of the world coming down.

But, what the CO2 is doing,

is changing the acidity of the oceans.

CO2 in the air, CO2 absorbs to the water.

Straight physics.

There's no political agenda here, just straight physics.

What does that do to the animal life in the ocean?

Well, it affects it.

It stops being able to make its skeletons.

The corals won't be able to lay themselves down.

But everything that's making the oxygen in the ocean today,

the zooplankton, the whole, you know, is related to the water chemistry.

[gentle music playing]

[narrator] As we can see,

this coral reef is a highly sensitive and fragile structure.

And since the reef is home to thousands of other species,

this presents a grave danger.

Their branching structures don't just offer protection

to other creatures,

their miraculous ability

is the transformation of nutrient-poor areas

into flourishing oases.

Some species such as the triggerfish are specialized in eating corals.

Without this highly specific source of food,

they would quickly starve out.

The difference between a flat and bleak bottom

below the surface

can easily be noticed in these borderlands.

In comparison to the areas covered in corals,

the stark sand is lifeless in these areas,

making it a marine counterpart of a desert.

The little fish can find almost nothing to eat in these regions,

which is why very few of them ever come here.

And when there's no little fish,

the larger carnivores can hardly find anything to eat as well.

The whitetip reef shark is one of those.

But for us, it's a chance to take a closer look at this creature.

The whitetip reef shark is a comparatively smaller shark

from the subspecies of the requiem sharks.

Its typical body length measures 1.6 meters

when fully grown.

Normally, they weigh a mere 18 kilograms,

making the whitetip reef shark a true lightweight

among the other kinds of sharks.

A great white shark can weigh up to 3.5 tons,

making it almost 200 times as heavy.

The whitetip reef shark is recognized

by the white tip of his first back fin.

Sometimes, other fins have the same coloring.

[upbeat music continues]

Further characteristics are the slender body

and the short and broad head with its rounded nose.

As its name suggests, this shark lives almost entirely near coral reefs.

[upbeat music playing]

As we can see here,

the whitetip reef shark moves

with the help of an intense wriggling movement.

In contrast to the other types of requiem sharks,

he can remain on the sea floor for long periods of time

without making a single move while pumping breathing water

through its gills.

This almost makes it look

as if the shark is taking a rest in the cozy sand.

This impression grows

when other fellow whitetips join him by his side,

which happens on a regular basis.

Unlike other sharks,

these little fellas don't have a territorial behavior.

In other words, they aren't bothered by fellow whitetips

in their vicinity.

Whitetip reef sharks are loyal to their area.

Single individuals remain in the same part of the reef

for months and years, or they return after short trips.

It's rare that they swim across longer distances

and find a new place to settle down.

That's why their neighbors are of great importance

to the whitetips,

and John Rumney wishes that we humans

would take that into greater consideration.

As an individual in your house, in your apartment,

you're not allowed to put your waste in your neighbor's.

But it's okay if industry does it.

It's okay if we collectively do that.

Because it's not really visible.

But, the billions of dollars that are being spent

by the fossil fuel industry to lobby, influence decisions,

do false science and that, is really criminal.

Like, in the years to come,

there's now the war crime's court.

Well, there'll be crimes against humanity

by these present politicians

for their not listening to the facts,

not listening to the science

and making stewardship decisions.

[gentle music playing]

[narrator] That's why Rumney and his colleagues

would like to explore the reef on their own.

[soothing music playing]

They want to engage in independent studies

on what exactly goes on in the reef.

Part of that are dives during the night,

an activity that very few tourists

would even take into consideration.

However, it can be highly interesting

to look around the reef at night.

The first thing that one can notice, most of the fish are gone!

They hide in the reef,

and many of them have their own, familiar places

to which they return again and again.

No wonder, as dozens of nocturnal predators

happen to roam the reef.

But even the corals have an entirely different nightlife.

Many species only extend their tiny tentacles at night,

which they use to filter food from the water.

They are also fed by the symbiodinium,

but at night, their tentacles help them acquire additional plankton

from the water.

The skeletal growth of the algae also increases at night.

An enzyme that encourages this growth has been measured

at double amounts during nighttime.

The reproduction of many types of stone corals

is also controlled by the phases of the Moon.

But that's only one element

that makes it a complicated process among these creatures.

Most types of soft corals are male or female.

But there are exceptions that can be hermaphrodites,

meaning that they are both.

Depending on the kind,

there are two ways of reproduction among corals.

In the first and most common way,

egg cells and sperm are ejected into the water,

where they meet and fertilize.

However, the chance of a successful fertilization

is very slim.

That's why the act has to be well-coordinated

and perfectly timed.

Once the corals are successful,

the developed larva starts its life in a planktonic way

as it floats motionlessly through the water.

Only when it reaches a reef does it settle down

and convert itself into a founding polyp of a potential colony.

Another way of reproduction among corals

is the sole ejection of sperm.

It then fertilizes an egg cell

that remained with the polyp and hasn't been ejected.

The larva is given away into the water

after days or even weeks.

By that time, they're already prepared

for their transformation into a polyp.

As we can see, dozens of things can go wrong

in the reproduction process of corals,

but that's nothing compared to the problems that other species face

as a result of human influence on the seas.

The experts on the Great Barrier Reef agree

that something has to be done,

- and it has to be done urgently. - Don't just do business as usual.

Think.

[chuckles] Start thinking.

'Cause right now we don't see the symptoms.

We're just getting the fever.

You know, we're just starting to have

the, maybe the [coughs], coughing in the lungs.

Uh, so, you know, oh, "What are we gonna do?

What's our medical treatment?"

Well, stop putting CO2 in the air.

Find ways of pulling CO2 out of the air.

Just manage.

We're the ones, our standard of living,

our air conditioning, our heating,

our cars, our luxury,

all the science that we have and we're spending

is really part of the problem.

[gentle music playing]

[narrator] Of course, our technology doesn't only have a negative effect,

and that counts for the reef as well.

After all, it helps us in our research of these underwater worlds,

and as Rumney has said himself,

it's important to interest people in the reef

and sensitize them to its problems.

Electronic media can be of great help in this matter,

which is why we continue our journey

through the wonder world of the reef.

[gentle rhythmic music playing]

[narrator] Another stunning phenomenon that we witness are fish swarms.

It's common to spot fish in such groups,

but beneath that lies a complex mechanism.

Swarms can generally be divided into two groups,

the real and the unreal swarm.

Members of the real ones are fish,

such as the horse mackerel, the diagonal butterflyfish

and the bigeye.

A real swarm always consists of the same number of fish,

and most of the time, they're fish of the same kind and age group.

When they're left alone, they seem lost and irritated.

Once they're in a group, however,

they communicate with each other.

Swarm fish always swim the same distance

from and parallel to each other in the same direction.

[gentle music continues]

The fish often have a silver coloring,

which enables them to shine and blink in their maneuvers,

thereby irritating approaching predators.

[gentle rhythmic music continues]

The other types of fish are unreal swarm fish,

which have similar characteristics to the real ones.

They're also called "group fish."

However, they only gather when there's an imminent threat,

and these swarms consist of species of various kinds

and age groups.

But the advantages remain the same as in a real swarm.

Swimming in groups or swarms

increases the chances of survival for every single fish

in case of an attack through predators.

On his own, the fish would barely be able to escape.

Predatory fish are more efficient

when they concentrate on a single target

rather than multiple fish at once.

In addition, the large number of fish in a swarm

make it easier to detect an assailant early on.

Ironically, a large number of fish

often attracts some predators in the first place.

That's why building a swarm is only worth it

when the living space is vast

and when there's an abundant supply of food

to provide for the entire group.

Both of these factors are given in the reef by nature.

Additionally, swarms are a great advantage when on the hunt.

With the help of cunning hunting techniques,

such as the skillful surrounding or chasing,

the prey is hunted down faster and easier.

Here we can see a swarm of barracudas

that make use of this technique.

In some areas, divers fear these predatory fish

even more than they fear sharks.

Some types of Barracudas can grow to sizes of up to a meter,

and their big fangs can cause considerable damage.

Fully grown, Barracudas usually turn into rogues,

but when they're still young, they travel in swarms

to increase their chances of survival.

[gentle rhythmic music continues]

For us as spectators,

these colorful swarms present us with a selfish advantage.

They're a marvelous sight to see.

And it's that optical glory that attracts the masses of tourists.

But their presence in these areas is not just a blessing,

as they present this ecosystem with an ecological problem.

Tourism is, you know, definitely an issue.

Uh, but if people don't care, they won't do anything about it.

So, the more we can harness the passion

of someone that's seen the reef and experienced the bounty of nature,

then the more likely they will go home

and make more appropriate decisions.

So, it's very important to have the interpretation

and the explanations on the boat.

We basically created research/ecotourism

before it was even a word.

And we would do expeditions.

So we harness the tourist dollar

to fund the research and conservation.

And we've been doing that since '95.

So, there are standards, there are improvements.

We still burned diesel fuel,

but we then figured it out

and we were the first commercial vessel

to use recycled fish and chips oil to run our boat.

It's not that simple,

but certainly, if everything that is a plug-in economy,

everything in every home and every industry is clean,

that's a really good start.

[gentle rhythmic music playing]

[narrator] John Rumney's passion is fueled to this day

by his experience in the 1970s.

In present day, experiencing the reef's entire glory and variety

is only possible in our fantasy,

a glory and variety he saw before his eyes in reality.

By making use of a color filter,

we can revive the atmosphere from the past

because these memories slowly fade out,

just like an old movie filmed in Super 8.

Of course, many of the species Rumney saw back then

can still be seen today.

One example is this trumpetfish.

Despite his amusing looks,

this creature is a flesh-eating predator.

His form, which might seem awkward to us,

is the trumpetfish's disguise.

Sometimes, this fish even stands upright

among soft corals and seaweed while imitating its movements

to appear entirely harmless.

But once the prey comes too close,

the trumpetfish seals its fate in rapid movements.

The triggerfish and the filefish,

who are far relatives of blowfish,

are more calm in their way of life.

They have a very stable jaw

which they can use to tear off stone corals and gnaw at them,

as we can see here.

[upbeat tropical music playing]

[narrator] But not all the species were as lucky

as the triggerfish or the trumpetfish.

Since the 1970s,

many life forms have been lost due to the decay of the reef.

Today, the Great Barrier Reef is different than it was in the past,

and that is clearly proven by the numbers.

But that's just why Rumney doesn't give up his fight

to at least preserve the present day status of the reef.

He doesn't object to tourism,

as he doesn't want to keep anybody from visiting and experiencing the reef.

But it's just that experience that he wants to keep from going extinct.

Currently, it seems as if future generations

won't have anything left of this beautiful reef.

That's why his approach is to explain the issue

to as many visitors as possible

and thereby sensitize them to the reef's problems.

Because it's not only the large companies and governments

who are important in averting the imminent danger.

We can all play a small part in protecting the reefs.

So, everybody can do little things,

but like yourself, everybody can start to look

and you go how much can they afford to do carbon offsets.

I, myself, and the Great Barrier Legacy

are involved with the pilot program

of creating the most intensive carbon sequencing experiment.

Because the normal force that you would plant the trees

is there's one in every three to five meters,

there's another tree.

And in 100 years they grew this big, etcetera.

So, that's positive, but that's very slow.

Whereas we've been doing experiments

to create the absolute most intensive carbon forests

that will be 80 to 90% carbon cubes

of, you know, 10 square meters, 20 square meters.

Uh, and that can accelerate the carbon absorption

hundreds and hundreds of percent.

So, this is a bit subtle,

but once there is a price on carbon

and if it's around $10 or more,

then the sugar cane industry, farmers,

may make more money with less work

by bringing carbon in, and that is a solution.

'Cause we not only have to stop what we're doing,

we have to pull back immense amounts

in order to get a stable temperature.

And we have two major threats.

The biggest, even identified

by the Great Barrier Reef Marine Park Authority,

is that the climate change,

the CO2 emission is causing increase in temperatures

and, therefore, will affect our reef.

The second, and what has been going on now for 100 years,

is the agricultural runoff,

which is the fertilizer, pesticides, silt going out, smothering the reef,

changing the chemistry of the water,

supporting an increased boom in crown-of-thorn starfish,

and therefore they're eating the reef.

I think what we need to do is invest in science

for best practice

and then what are the carrot and sticks to implement best practices.

If we as a society wanna save the Barrier Reef,

then we should help the farmer to get there.

It's not their fault.

I mean, they've been, you know, doing this for 100 years.

So, if now it's important to do,

we should make it financially viable for them to do that.

[rhythmic music playing]

[narrator] Just like the many different fish,

corals and other species cooperate in maintaining a functioning ecosystem.

We humans should work together in order to preserve this variety.

A typical symbol of environmental protection is seen here,

and it's one of the largest inhabitants of the Great Barrier Reef, the sea turtle.

There's a total of seven kinds of giant turtles,

six of which can be found at the Great Barrier Reef.

Despite their length of 1 1/2 meters and a weight of over 200 kilograms,

the sea turtle floats elegantly in the water.

Here, she's in her element as she glides through the sea

like a bird in the sky.

It's here where the sea turtle spends most of her life.

The sea turtle is not faithful to its habitat.

There's no one single place in which it lives.

Every year, the sea turtle travels over far distances.

In the beginning of its life,

the sea turtle feeds on crabs and jellyfish,

as well as on fish eggs.

When it grows older, however, it turns into a vegetarian.

A sea turtle can reach ages of up to 50 years.

As mentioned before, the sea turtle is a threatened species.

The main reason is its popularity as a delicacy in Asian countries,

as well as the use of its shell in the crafting of accessories and charms.

Since 1979, it's illegal to catch and trade with sea turtles.

Nevertheless, thousands die every year

as they are hunted illegally or caught along with crab fish.

It's another example of the ignorance

that some people display in their treatment of marine species.

[gentle rhythmic music playing]

[narrator] It's this very behavior that John Rumney denounces

as he wishes that people would have more respect

for their environment and would start to give it more thought.

If that doesn't happen,

the condition of these breathtaking reefs and its sympathetic inhabitants

will worsen significantly.

Australia is now leading the world in being, you know, arrogant

and really, really stupid in trying to--

'Cause they are listening to their fossil fuel industry lobby groups

and really making decisions based strictly on that.

There's so much evidence that, you know,

in the common jargon, from the common people,

there's protests and it's like "Coral, not coal."

All right? Keep your coal in the ground and we have a chance.

If you keep putting the coal, CO2, in the air,

we're gonna reach tipping points and we don't even know where this--

You know we had these estimated temperature rises?

That does not even begin to calculate

the methane in the tundra and all these other things that may happen.

And they-- You know, huge areas of Africa and the Middle East

and Australia will be uninhabitable

with four to six degrees more centigrade in temperature.

So, that's where we're heading.

That is business as usual.

[gentle music playing]

[narrator] For many years now,

Rumney has been actively engaged in the protection of the reefs.

That's why he can be considered a trouper

or even a veteran of the reef.

But among the inhabitants of the reef,

there lives someone who's a real old-timer,

in the literal sense of the word: the giant clam.

Giant clams can reach an age of up to 100 years.

Their tough, enduring shells,

which remain well after they pass on, can grow even older.

The great giant clam is the largest of all known species of clams.

They can reach lengths of up to 140 centimeters

and a body mass of up to 400 kilograms.

All giant clams live in the Indo-Pacific region

and populate coral reefs.

They live together with symbiotic algae

that live in their lips and provide the clam

with food and oxygen.

For quite some time now,

giant clams are a threatened species due to overfishing and pollution.

That's why they're now under species conservation.

There are attempts to conserve this species

by aimed breeding.

As giant clams can form large pearls,

they are often subjects of myths and legends.

Sometimes, they're called murder clams,

as they supposedly snap for divers and other species

and keep them from escaping the depths of the sea.

In reality, the closing movement of clams is very slow.

The enormous diversity of species in the coral reefs

brings up new discoveries on a regular basis.

Despite the many fish that we're familiar with,

we find out just how complex and interesting corals are

as they are very different in comparison to other life forms.

But in their many different forms and colors

that can be observed in every part of the reef,

they are not alone in their eccentricity.

Here he have another obscure life form,

similar in its color to these bluish corals: a starfish.

This creature appears in the form of a five-armed figure.

The arms can almost remind one of a bunch of sausages,

but they can also have the appearance

of a traditional star with five straight ends.

Or it can be so round that it almost looks

like an urchin that lost all of its needles.

Many starfish can reproduce lost limbs

when they're torn off by other fish

or they can even drop them for their protection.

Far relatives of the starfish are the sea cucumbers.

At first glance, one might not even recognize them

as an echinoderm, a life form with needles

growing from its skin,

as they don't have the usual five straight ends.

The muscular and elongated body

has an opening for a mouth at its front end,

surrounded by five rows of tentacles,

a characteristic that gives insight to its relation to other life forms.

Instead of a skeleton,

the sea cucumber has a strong hose of muscles

consisting of ring lengthwise musculature.

This sediment-eating kind, which we see here,

crawls across the sea floor

and thereby gathers the sediment that contains organic components.

Those parts that the sea cucumber can use are digested

while the indigestible, mineral sediment is excreted.

That's why these sea cucumbers can also be called

the vacuum cleaners of the sea.

They help in keeping the reef clean and tidy.

Even though they're not a pretty sight to see,

sea cucumbers have interesting characteristics,

as well as an important task in the reef

that isn't evident on first sight.

If we as humans want to understand these relations,

we have to conduct further research.

Even at the Great Barrier Reef,

not all of its species are yet known to man.

In fact, every time we do a research expedition

with experts that know a certain thing, we find new species.

So, we're potentially destroying it

before we've found half of what's there.

With the latest bleaching,

we have definitely knocked off

a majority of certain species of corals that are in the shallows.

Now, there are sink reefs that are deeper,

that are farther away, that can reseed these

if the conditions come back to normal.

In the 100,000 or 200,000 or a million year view,

the corals are gonna be fine,

because we'll be gone and those cycles will regenerate.

It might even take millions of years

for it to go through the dead sea, you know,

acid ocean, to then come back.

We've done it millions of years ago, we'll do it again.

But, for us to enjoy the Barrier Reef and eat fish,

to do what we enjoy doing on the reef,

but reefs worldwide,

then I would say we are definitely heading that way.

Uh, WWF has estimated something

like from a 50 to 120 species

are lost per day on the planet.

[somber music playing]

[narrator] These numbers are more than unsettling,

as they show that even the greatest variety of species

can shrink to just a number of specimens

in the shortest amount of time.

A great example for a multi-variant species

are the groupers.

These cozy-looking fish make up a family

of more than 160 different types.

The giant grouper is one of them.

One of the biggest fish ever discovered in the reef.

He can reach sizes of up to two meters.

Most types, however, reach sizes between 20 and 80 centimeters.

They're easily recognized by their prominent jaw

and their seemingly big lips.

Their back fins reach all the way from their head

to their tail fin

and sometimes they even have spikes on their upper part.

Groupers only gather in larger groups for reproduction.

Other than that, they mostly live on their own.

They mostly protect a certain territory in the reef,

or at least their own caves.

And about caves,

the many caverns and hiding places in the reef

are a great advantage of this habitat.

Even larger types of fish enjoy the protection

of these limestone structures.

Sometimes even in larger groups, as we can see here.

Because it's not only the groupers that place great importance

on their very own cave.

A creature that is especially serious

about the protection of its home is the moray.

This creature, looking similar to a snake

as it doesn't have any fins, has a very sharp set of teeth,

forcing intrusive divers to be careful with their fingers.

And the Great Barrier Reef, with its vast coral reefs,

offers the perfect hiding place for these creatures.

Depending on its size, a moray can have multiple hideouts

that may lie apart for up to 200 meters.

Smaller types of morays almost never leave their home

and only hunt inside their caves.

Larger morays are also faithful to their homes,

and only leave it for reproduction purposes

or to go on the hunt for prey.

Groupers are also carnivores.

Their diet normally consists of fish and crablike creatures.

In order to catch their prey, they rapidly open their mouths,

thereby creating a pull that sucks incautious fish and crabs

straight into their mouths.

Groupers spawn in open water,

and most species let their eggs float off into the open sea.

[electronic music playing]

There, the larvae are safe from other fish.

The young fish return to the reef once they grew up a little.

Therefore, the groupers are another highly diverse species

whose way of life depends entirely on the reef,

just like with most of the species that live here.

If humanity doesn't want to lose this rich diversity,

something has to happen soon.

[electronic music continues]

Don't just do business as usual.

Think, stop putting CO2 in the air.

Find ways of pulling CO2 out of the air.

The sooner we stop, the sooner we have a chance

of having a healthier world.

The Great Barrier Reef

is just one of the most magnificent places on the planet.

It's still fantastic to come here.

It's worth saving, so let's get on with it.

[gentle music playing]

[narrator] A clear message from John Rumney

whose passion and energy will hopefully inspire many people

to become active in the field of environmental protection.

But the most convincing plea comes from the reefs themselves.

Beaming with all of nature's splendor,

they are a symbol for life on Earth.

[gentle music continues]

While we let these pictures sink in,

we should keep one thing in mind.

All these fascinating species which we've met on our journey

are potentially endangered.

Nobody should have a bad feeling when enjoying this splendor,

but we should never forget,

despite only covering about 0.2% of the seafloor,

they are home to more than 30% of all of marine life.

[gentle upbeat music playing]

Every little thing we can do throughout our day

to reduce our emissions of carbon dioxide

is of great importance.

This way, we can preserve the splendor of the Great Barrier Reef

for future generations,

who will be able to enjoy it with the same awe as we do now.

[louder upbeat music playing]

[lively music playing]