All language subtitles for BBC.Our.Changing.Planet.Series.3.1080p.HDTV.x265.AAC.MVGroup.org

Coral reefs cover just 1% of the ocean floor

and yet they're home to a quarter
of all marine life.

This is totally overwhelming.

A complete sensory overload.

It's extraordinary.

Reefs feed us and keep us safe,

shielding coastlines from storm
surges and rising sea levels.

But the corals that live
in warm, clear waters

face a multitude of challenges
that threaten their very existence.

Half of all reefs are already dead
or damaged, and without action,

we could lose most of what's left
in the next 20 to 30 years.

Scientists all over the world
are racing to try

and find creative solutions.

Just about anything they can do
to give corals a helping hand.

In this, the third series
of Our Changing Planet,

where we look at
precious ecosystems,

and the people trying
to save them.

We're focusing on the habitat

that's facing the most
urgent threat - our coral reefs.

I'm taking a look at high-tech,
creative and imaginative solutions

to the coral crisis that are being
developed on dry land here in the UK

and also in the US.

On their own, none of these projects
can save our reefs,

but the hope is that together
they'll deliver a crucial

lifeline and a much-needed
conservation success story.

I'm back in the Maldives, where
a pioneering team of scientists

is attempting to regrow a damaged
reef by helping it

to reproduce more effectively.

It's going to be exhilarating.
Seat-of-our-pants kind of science.

Nice work!

It's a ground-breaking,
astonishing idea

to combine a fertility treatment
for corals with, incredibly,

a soundtrack of fish vocalisations
to bring life back to this reef.

It's a world-first so no-one knows
if we can pull it off.

If it works, it's going to be
a global game-changer.

The Maldives is the flattest
country on Earth,

much of it just 90 centimetres
above the waves.

These reefs act as a living shield,

protecting half a million people
that live here from the sea.

They're also home to a dazzling
number of animals.

There may be as many as a million
different species that rely

on coral reefs to survive.

They have a baffling array
of different forms - tables,

vases, branching stag horns,
great massifs like this -

some of which could be
2,000 years old.

Despite that, they are now
in serious trouble.

We've lost approximately 50%
of corals in my lifetime.

Corals are living creatures,
sensitive to rising temperatures.

When the sea is too warm for long
periods, the corals get stressed

and eject the microscopic algae
living within them.

These normally act
like solar panels,

providing most of
the coral's energy.

Without them,
the corals turn white and starve.

It's known as bleaching.

This reef was hit really hard
in the 2016 bleaching event.

73% of corals died.

But there were survivors, which must
have some natural resilience

to increased temperature

that they're likely to
pass on to their offspring.

That could be the key to long-term
recovery here, but there are

so few of them that they
might struggle to do it naturally.

OK, we need to bring some back.

So, to save this reef, scientists
are converging on the Maldives

to help these surviving corals
breed more successfully.

Corals start life as tiny
floating larvae

that settle on solid surfaces,

replicate themselves,

and build hard external skeletons.

The structure we see is
a colony of thousands

of genetically identical animals
all living together.

But one of the drawbacks is once
you've settled, you can't move.

So, how do you go about breeding?

Well, that is one of the most
exciting spectacles in nature.

On just a few nights a year,

triggered by a full moon,

corals release millions of eggs
and sperm into the water

in a process called spawning,

where they fertilise
and become larval corals

looking for a place to settle.

It's this miraculous spawning
process that has become

the life's work of one of the
world's leading coral scientists.

The real challenge we face is we
need to produce a lot more larvae

than are currently being
naturally produced.

Professor Peter Harrison is a coral
expert who has spent 40 years

studying Australia's
Great Barrier Reef.

He pioneered a revolutionary
technique known as coral IVF.

Peter collects spawn from the wild,

artificially fertilises it,

grows the larvae in specially
designed protective pools,

and then, when they're ready,
he releases them back onto the reef.

We target the release of those
larvae onto degraded parts

of the reef to kick-start
the recovery.

Back to me.
Down, down, down, down.

The first stage in the process is to
collect as much spawn as possible.

Corals here only spawn a few times a
year, so we can't afford to miss it.

This multi-national team
are straight in the water,

carefully checking each surviving
coral for colourful eggs,

a sign that spawning is close.

Once replaced, the fragments will
repair themselves and regrow.

Time is tight,
so we work long into the night.

Below the waves,
it's an unearthly scene.

Some corals contain a fluorescent
protein that glows

in our UV torchlight.

I feel like I've been transported
into a scene

from a 1970s Star Trek movie.

Everything looks so surreal,

transformed into a whole different
world of colour

I've never seen before.

Utterly dazzling.

Beautiful as it is, we're not here
to take in the view -

there's work to be done.

This is kind of the magic part
of what's being called coral IVF.

The team have identified,
during the daytime,

colonies of corals
that are ready to spawn,

and they're tagged.

Once they're ready, they'll release
their sexual cells and they're

pretty much cast adrift and at the
mercy of the elements and predators.

The damage to this reef means
there are too few reproductive

adult corals spread across a very
large area, so when they spawn,

there's little chance of the eggs
meeting sperm and fertilising.

But we have a way
of increasing our odds -

using this cone,

a gamete trap which almost functions

like a coral condom.

The bundles of egg
and sperm will be released up

into the pot on the top...

..and that is going to be
the raw material

that helps us do the experiments

that could be a massive part of the
potential future of these reefs.

In the wild,
out of a million larvae,

maybe one will make it to adulthood.

On the Great Barrier Reef,
Peter's coral IVF has made

larval survival up to 100 times
more likely.

And one advantage of the coral
we're working on here

is that any offspring
that do survive could grow

an impressive ten centimetres a year

and be sexually mature
in just three.

Now the traps are in place,

we could be waiting for days
before the coral spawns.

You never know what
they're going to do.

These branching corals that we
are expecting to see spawn here,

they are quite variable
in their timings, and in some cases,

they wait until seven or eight
nights after the full moon.

They're amongst the simplest
animals on our planet

but they're very complex
and they keep us guessing.

Suddenly, on our first night,

there's a buzz of excitement.

Word is that one of the colonies has
started spawning.

Didn't expect it to spawn tonight,

but you can't predict corals,
apparently.

I'd come here expecting to be
waiting for days, maybe even weeks,

for this extraordinary spectacle
to take place,

and right now one of the most
special and important events

in the whole natural world,

and certainly in our seas,

is happening beneath us right now.

It might be unexpectedly early
but we're ready for it -

the coral condoms are in place

and the nursery pools are ready to
receive and protect the harvest.

But mixed with excitement
is trepidation.

Spawning in the Maldives
is different

to that on the Great Barrier Reef
where Peter usually works.

We don't know if these corals
will spawn together,

or in great enough quantities
for the experiment to continue.

It's happening!

Across this brutalised reef,

the surviving adult corals
are in full reproductive flow.

Hundreds of thousands,
maybe millions of eggs and sperm,

are rising upwards.

The cells are full of fat
so they float, and this is key.

If the cells drifted at different
levels in the sea

they might not bump into each other
and fertilise.

Because they all rise to the
surface, mixing is much more likely.

So, already the gamete traps
are working their magic.

Inside, you can see the precious
sexual cells gathering at the top.

The potential future of this reef.

There are so few of each
type of adult corals here,

that it's possible that none of the
spawn would fertilise naturally.

There's so much riding on the
success of Peter's IVF attempt.

Every stage completed
feels like an obstacle overcome.

Well done. Congratulations.
What an amazing job!

Spawn is being collected
all across the reef tonight.

Mm, beautiful.

Eggs and sperm from the same colony

don't normally self-fertilise.

What we need to do is mix all the
eggs and sperm from as many colonies

as possible to get as much genetic
diversity amongst the larvae.

On the damaged reef, less than
5% of the spawn will be fertilised,

but in the containers,
the fertilisation rate exceeds 95%.

Cheers all around.

THEY CHEER

Well done, team.

It's been a long
but successful night.

As the sun rises,

the now fertilised spawn
is very cautiously transferred

into protective pools

where it will spend a few
critical days developing.

But it's not all good news.

There's not as much spawn
as we'd hoped for -

only enough to fill
one of the nursery pools.

A stark reminder of how hard
these reefs have been hit.

Even the spawn that we have managed
to collect is in danger.

A storm is approaching the island.

THUNDER RUMBLES

The spawn is floating on
the sea surface,

and a downpour of fresh water
can kill it

before life has even had a chance.

If that happens,
the rescue project will be abandoned

and we'll all be going home early.

It's going to be a sleepless night.

When you're doing coral
conservation work on the open sea,

you've little control
over the elements.

And for something as precious
and specialised as coral spawning,

it would be really useful
to be able to manage at least

some of the conditions to maximise
the chances of success.

And that's exactly what scientists
are doing here in South London.

Inside this unassuming warehouse is
a ground-breaking research facility

exploring novel ways to
culture corals on land,

that could then be planted
out in the ocean.

The scientists here were the first
in the world to work out

how to trigger coral spawning
in captivity by mimicking

some of the natural conditions
they need.

We have been trying to get corals
to breed and to grow quicker,

survive better, and really impart
some of that knowledge

on the rest of the world, really.

In the wild, mass spawning
is a highly coordinated event...

..with the corals relying
on environmental signals

like moonlight and temperature.

When all the cues are just right,

the ocean is filled with
masses of released eggs and sperm.

How on earth do you begin to do
that in a laboratory situation?

All of these types of things
can be done in aquariums.

We managed to get corals to spawn
in about eight months

after putting all this in place.

We knew 100% we were onto something.

Jamie and the team have developed
a ready-to-use

coral spawning system that can be
shipped around the world

and can be controlled
from a mobile phone.

Oh, it looks beautiful in here.

So, this is a spawning system.
OK.

The reason why we're standing
in something that looks like

a photography blackout studio,

which means we can walk in
and out of here

and block any external light.

Then we can slide these across
and we can completely enclose

the corals, because we don't want
to be coming in and out of here

and putting light all over them

and ruining that cue that they need
to release their eggs and sperm.

OK. And when it comes to moonlight,
how did you find out how you could

replicate that moonlight here,
how strong it had to be?

We know that full moon
is about 0.1 lux.

It's a really small amount of light.

One lux is the amount of light

you can detect from a single
candle a metre away,

so 0.1 lux is actually very faint.

I have a light meter

and I went round waving it around
in my garden at full moon.

You didn't?
I did.

And then trying to get the amount
of light from an LED to match

that intensity of light, but also
the colour of the moon as well.

Once Jamie had control of the timing
and quality of the light,

he could manipulate the corals
into spawning more often,

essentially speeding up
coral reproduction.

And now the lab is growing a whole
raft of healthy young corals,

at different stages of development
in a series of nursery tanks.

What are your ambitions for this
system going forward?

You imagine you go to a farm now,
vast greenhouses producing

millions of plants
to go into people's gardens.

You know, this has the same
potential to do that,

but to go onto reefs.

We want to see this
on colossal scale,

producing millions of corals a year.

It won't be able to rebuild
the reefs

the way they were 50 years ago.

It will buy time until we can sort
out the bigger issues

that are facing our planet.

And it's working.

70 spawning systems
have already been shipped

to coral restoration projects
all around the world,

with new, healthy corals being
planted out onto reefs in the wild.

STEVE: After a stormy night
in the Maldives,

it's a peaceful but tense morning.

Our precious cargo is contained

within those floating pontoons
out there.

At this stage, they're incredibly
susceptible to any changes

in the environment, and last
night, we had torrential rain.

Peter designed these nursery pools.

They allow the fertilised spawn

to develop into larvae in natural
conditions,

but the fine mesh prevents them
being swept away or eaten.

The team are taking samples
to check for signs of life.

To get a decent sample size,
we need to stir it up.

Ah, this is amazing.
It's like stirring

the most expensive witch's cauldron
in history. Exactly, yeah.

Right now, to the untrained eye,
these larvae are almost invisible,

but Peter and his team
know what they're looking for.

There's one.

There's over 600,000 in here
and you've got one!

Yeah. So some of those...
THEY LAUGH

We try again.

Come on up, my lovelies.

Oh, yeah.
Beautiful.

Ah, that's more like it!

That's where they all are.

So, basically,
my stirring wasn't good enough!

Yeah, sorry.
You didn't stir the pot enough.

You gave me one job!

One job. Oh, no!

There's literally
many hundreds there,

probably a few thousand.

I was seriously worried that we
might just have had too much rain.

Exactly.
I mean, that's the whole thing.

Every stage of this process,

like life for a coral naturally,

is full of risk.

Because they're so tiny, it's hard
to think of the larvae as creatures,

but these are baby animals.

Thankfully, the majority
of the larvae have survived,

which means we're still on track.

LIZ: Life for a developing coral
is filled with jeopardy.

If it's not warming seas
or intense storms,

it's explosions of algal blooms.

Not the vital microscopic algae
that live inside the coral's tissues

but larger species of algae
that can smother and kill the coral.

I am back at the coral spawning lab
in London, where Jamie

and the team have developed
an ingenious system for breeding

and growing thousands
of corals in captivity.

But this conservation breakthrough
is under threat from algae.

On a healthy reef, algae are
normally kept in check by herbivores

like turtles and crabs but here
in the lab, with no grazing animals,

the algae can quickly grow
out of control,

swamping the growing coral
and killing as much as 95% of it.

Now, Professor Michael Sweet has
developed an ingenious solution

that's entirely natural.

Don't get spiked.

Well, don't spike me!

This is an adult urchin,
it's called a tuxedo urchin,

largely because of the sort of
shiny blue, blue black colouration

in between those spines.

There are around 950 species
of sea urchins in our oceans.

Related to starfish,
they move across the seafloor

on tubular feet that they also
use to attach themselves to rocks.

So, why harness
the power of sea urchins

when it came to your problem
with the algae?

So, urchins are,
are common-or-garden,

they're found all over
the place, really,

and they're massive herbivores.

So they're really interesting,

and as all are herbivores,
they have a very big stomach

for the size of the animal, so they
can actually eat quite a lot.

And what they like to eat is algae.

In the wild, urchins make light
work of any algae they come across.

But that voracious appetite
can sometimes be a problem

if another species
gets in their way.

If we put these guys in the tanks,

they'll bulldoze
over our baby corals.

They're not targeting the corals,
they're doing it inadvertently.

As they're feeding? Exactly, yeah.

The answer was to think small,
matching the size of the urchins

to the coral, with the two species
growing in size, together.

And it all comes down
to perfect timing.

We know where the corals are going
to be spawning and then we need

to target that same spawn date
for our urchins.

But that's another huge challenge.
How do you time it?

With urchins it's actually
relatively simple

and we can hopefully show you
how that works now.

We're going to give them a little
spa treatment in a nice warm bath.

A spa treatment? Exactly.
Very scientific, Mike.

As long as I don't have to give them
a massage!

Moving the urchins to warmer water

triggers the release of their eggs
and sperm,

just like corals in response to
environmental cues like moonlight.

This guy looks quite happy.

In the sense that he's ready?
He's waving his arms around, so...

How do you define a happy urchin,
ready to spawn?

I mean, for goodness' sake.

A male spawns first,

releasing its sperm in plumes

from openings called gonopores.

There's a beautiful slow-moving
cloud emanating from the top.

And then a female releases
a cloud of eggs,

wafting them through the water.

Got the eggs coming in the female
now. Oh, look at the eggs! Yeah.

Oh, this is... This is amazing.

This is just so amazing.

It's just a beautiful thing that's
happening in a tiny little tank

in an industrial estate in London.

Once the corals and urchins
have developed for several weeks,

it's time to introduce them
to each other.

So these little babies are about
two months old.

This is the Holy Grail.
This is exactly what we want.

Actually, on these plugs are baby
coral, so little corals which have

just settled and now the urchins are
doing their job,

cleaning up those little bits
of algae

and making sure our corals
can survive.

The babies will grow together,
and by eight months old,

the corals will be robust enough
to survive the bigger urchins.

By adding baby urchins to their
coral nurseries, Mike and the team

have increased the number of corals
surviving by more than 40%.

It's a smart solution,

inspired by what sea urchins
do naturally in the wild.

But on the east coast of the US,
there's a problem.

The importance of sea urchins
for coral survival has sadly been

all too evident off the coast
of Florida recently.

In 2022, a disease wiped out
huge numbers of urchins,

and in their absence,

algae smothered miles of coral
on an already endangered reef.

Scientists at Mote Marine Laboratory
in Florida

monitor the complex interactions
on the reefs here,

looking for ways
to restore the balance.

When we don't have enough
herbivores on the reef,

eating the algae as it's growing,
it can get out of hand,

it can get overgrown and it can
absolutely smother corals

or even engage in kind of chemical
warfare with corals,

and cause disease and other things
that really are a problem.

Algae also cover up the space that
little baby corals need to settle

and make it so that they can't find
a place to settle

and become a new coral colony.

So, essentially, there are no
babies on reefs with too much algae.

The parasitic disease that
killed 98% of Florida's sea urchins

currently has no cure, so Jason
is looking for another native

species to rescue the reefs
from the overgrowing algae.

This is the Caribbean king crab.

This is a very large male.

They're phenomenal herbivores.

They eat algae and they eat
algae that other stuff won't.

More algae than most of the urchins
in the region as well.

Jason believes that these crabs
could be the answer.

In field tests, we increase
the density of these crabs

by about a millionfold
from one per square kilometre

to one per square metre
on these small test reefs

and over the course of one year,

they graze the algae down
by about 85%.

So, we're very confident that these
are excellent candidates

for grazing on coral reefs.

But the number of crabs needed
to make a real difference

is mind-boggling.

Just to meet the needs for seven
of the reefs that we're working on,

we're going to need to produce
2.8 million crabs.

To create the army he needs, Jason
has set up an enormous crab nursery.

Here's a little baby right here.

You can see him on my finger now.

This little guy could be
the size of that larger male

in eight to ten months from now.

They're just a dream to work with.

Once the shells
measure three centimetres across,

the crabs are reef-ready.

From hatching to release
takes less than five months.

By carefully nurturing the
mums and babies,

Jason and the team aim to produce
250,000 juvenile crabs a year

to release onto Florida's reefs,

increasing the population density
a millionfold.

It might seem like a crazy strategy,

but Jason believes
the risks are low.

First, they're a native species
that naturally occur throughout

the entire region,
and all we're doing is

increasing their density to fill
this functional void on the reefs.

The team will monitor the reef
for any potential adverse effects,

but, ultimately, more crabs means
more food for predators,

which can lead to more marine life
and in turn, a healthier coral reef.

It could just be a solution
to this urgent problem.

STEVE: In the Maldives, Peter has
used his coral IVF method

to produce half a million
coral larvae.

The first stage is complete.

Peter's work has already helped
damaged reefs come back

to life elsewhere, and the process
has enormous global potential,

but there's always been one factor
standing in his way.

We know that when we release tens
of millions of larvae from these

pools, they disperse over the reef,
some of them get eaten by fish,

some of them drift off the reef
and are never seen again.

The weak spot in the process
is maximising the settlement

of those larvae
on the target reef areas

that we're really interested
in restoring.

Now, for the first time ever,
Peter is collaborating

with a scientist who thinks
he may have a solution.

I've been fascinated by how
corals find a reef

and choose where they're going
to make their home.

Professor Steve Simpson
is a bio acoustics expert

from Bristol University in the UK.

In the last series, I was with Steve
and his team when they made

the breakthrough discovery
that tiny larval coral,

with no ears and no brain,

are attracted to the sounds
of a healthy reef.

Hang on, hold the phone!

You're talking about teeny tiny
floating larvae hearing a reef?

Absolutely.

In fact, the team discovered
that it's the sounds of the fish

that are the trigger for coral to
sink to the bottom and set up home.

Look at that.

It looks like a meteorite.

Fish song is what encourages coral
to build a reef.

Boof!
THEY LAUGH

Steve's audacious plan is to use
recordings of fish to lure

the millions of larvae produced
by Peter's fertility treatment,

to set up home and resuscitate
this stricken reef.

What we need to do now is work out
what sorts of reef song

is most likely to start
attracting larvae.

And if we can do that,
that could be incredibly important.

I mean, it feels almost like a bit
of a Live Aid for the coral reef.

So, you're Bob Geldof,
what does that make you?

Midge Ure, I guess!
Obviously, yeah!

The whole idea of a meeting of minds
is incredibly exciting,

but, I mean, it sounds to me like
all this stuff should take decades

to figure out with experiments.
We've got, like, a week.

We are going to have to work
at an absolute rate of knots.

It's going to be exhilarating,
seat-of-our-pants kind of science.

There's no time to lose.

Our first challenge is how to record
the sound of a healthy reef,

so we're travelling to a reef
called Hassan Haa,

that we know is full of life.

Last year we tested a rudimentary
prototype of giant swimming ears

for just this moment,

and Steve thinks he's finally
cracked the design.

You remember how sometimes it was

just kind of hanging a bit
loose in the water?

We've now got it basically modelled
on a underwater paper aeroplane.

So, we've got this huge tail
at the end.

I'm hoping that, underwater,
this is going to glide silently.

There's only one way to find out.

Time for the maiden voyage!

As we glide over the reef,

four giant ears pick up every groan,
shriek and whistle.

RAPID CLICKING

I'm retreating to a safe distance

so as not to disturb
the crucial recordings.

It's the most incredible thought,

that these fish around me right now
have their own songs.

Wow! Look at this!

Clownfish have an amazing attitude.

They will protect their anemone home
with their life, if needs be.

And the sounds they make

while they're doing it
are just extraordinary.

WATERY GURGLE
Did you hear that?

Did you hear that as it came
towards me? Unbelievable!

It just did it right then.

How's about that?
I have never heard that before.

But in all likelihood,

that's probably just cos
I haven't been listening properly.

WATERY GRUMBLING

That is the first time I've been
given a telling off by a fish!

When we get back to the boat,

we're both thrilled by what
we've seen and heard.

It's super, super exciting

and seeing the amount of life down
there and the amount of diversity...

I know. Well, what a reef
to take it to, eh?

The first time it ever gets to
record a reef

and it's a reef like that.
Beautiful.

Soon there are hundreds of hours
of data to crunch...

..and now the pressure's on.

By the time the larvae
are mature enough to start looking

for somewhere to settle down,

Steve needs to have selected
the best sounds to attract them.

But he's discovering that the
recordings vary enormously.

So, here we've got midnight.

RAPID RATTLING
Can you hear those?

"Do-do do-doo. Do-do do-doo."

WATERY GROAN

And then that groan. "Grrrrr."

So we've got a lot of fish
activity here.

These are all nocturnal predators,
and they really use sound

as a way of keeping
the hunting pack together.

They're like a bunch of wolves
out on the reef,

and they're howling to each other
when they find potential food.

CRACKLING

Throughout the day, different
animals dominate the recordings.

One that I have to say I'm most
excited about hearing is

the dawn chorus.
Right, OK. So, the dawn chorus.

This is where you've got the
emergence of all the daytime fish.

CRACKLES

So, you've got this,
"Bup-bup-bup, bup-bup-bup,"

that's the kind of clownfish sounds
that you tend to find.

"Brrrp. Bup-bup."

Very obvious, just these differences
in the soundscapes.

Begging the question,

do coral respond differently
to different recordings?

Steve had planned to run
multiple experiments

with large numbers of larvae,
but because the damaged reef

has produced far less spawn
then expected,

Steve has to limit his experiments.

So, he's forced to test a hunch
that busy is best.

Steve thinks the recordings from the
vibrant and varied healthy reef

could be the most effective.

What we're hoping, I guess,

is that those teeny tiny corals
can tell the difference. Mm. Yeah.

We're going to put them
into the choice chambers,

play these different sounds
from one end or the other,

and then look to see the directional
movement of our coral larvae.

I'm nervous, I've got to tell you.
I'm very nervous!

And in the lab, things go to plan.

Steve thinks he's cracked it.

The larvae actively move towards
the sound of the busiest locations.

But now we have to test it again,
under natural conditions.

And that's no mean feat.

This has never been done before.

It's one of those moments where
science is actually happening,

and to get in there and watch
is really quite an honour.

OK, so this is the moment of truth.

We have our cylinder
suspended in the water.

The speaker underneath it
with the sounds coming up,

and Peter has in his fingers,

just a few of those precious larvae
to enter into the system.

OK, we've got one.

So you can see one of the larvae
inside, quite clearly.

So now we're going to switch
on the sounds of a healthy reef.

CRACKLING
Oh, I can feel it and I can hear it.

I really can't quite believe
we're doing this.

That one there has
definitely dropped.

Yeah.

What about that one, Peter?
You think that's dropping as well?

It went from here to here.

It went corkscrewing down.

It can see a home!

And they're all down to the bottom.

Six of them.

So best-case scenario
was for these larvae to start to

make their way down towards
the sounds of the healthy reef,

which are coming from below.

And it very much seems
that that is what's happening.

You happy? Good news!

That is absolutely fantastic.

And now that we know that
in principle this can work,

the next stage has to be release
enormous amounts of these

larvae and try and create something
big and something special.

How exciting is that?

Nice work!

Natural reef restoration takes time,
but some of the options being

explored could help to
speed things up.

Coral reefs are not exclusive
to warm tropical

waters like those
found in the Maldives.

Here in the UK, cold waters harbour
incredible reefs too,

and they're just as important
and precious.

A coral reef is built from the hard
calcium carbonate

skeletons of stony corals.

But a reef can also be made
up of other marine species.

Mussels and oysters tightly packed
together and attached to old

shells, rocks and sandy material
also create solid reef structures,

providing homes for a variety
of species, including soft corals.

The UK has around 60
species of soft coral,

and as their name suggests,
they don't grow a hard exoskeleton.

Most develop fleshy and flexible
tissues like tentacles.

But just like their stony
coral cousins,

their larvae need a stable
surface to grow on.

Around the world, reef
structures have been

destroyed by activities
like dredging and trawler fishing.

The resulting marine wastelands
are no good for corals to settle on.

On an industrial estate in Cornwall,
a band of resourceful school friends

decided to come up with a novel
solution to bring back their reefs.

So this is how we started.

Our first-ever mixer
was 120 quid off eBay.

This is...this is literally how you
did your first one?

So we literally went on to eBay,
bought a mixer for 120 quid,

and now it's gone from making
a couple, to thousands a day.

Tom Birbeck and his team
are producing the building blocks

of artificial reefs.

The cubes are made from 98%
recycled materials.

They're carbon-neutral,
and once lowered into place,

they start working immediately,
dispersing wave energy and providing

solid structures for soft corals
and other creatures to settle on.

Carefully designed nooks
and grooves on the cube's surface

will attract all
sorts of marine life,

each needing their own
very specific home.

Tell me a little bit about how this
all started for you.

So I started off spear fishing
with my dad at sort of ten, 11.

Erm, always used to catch fish.
Thought it was great.

Then about 15, 16, you'd barely
catch any fish. You know,

nothing, literally barren.

The actual rocky reef area that had
been destroyed, that won't regrow.

So we looked at trying to build
something ourselves and between us,

we've sort of carved out the
product that we think we can use.

The team are already manufacturing
the blocks on a large scale,

but because they can be produced
using simple tools

and materials, they're perfect
for restoration projects everywhere.

Why have I got a tiny
little... What's this about?

And you've got the big shovel.
This is really sexist!

Do you want to... Do you want to...
It's really sexist. I'm just saying!

No, I'll hang on to it cos it's less
work, but...

OK, we're pouring. We're pouring.
Right, OK.

What we're really lucky to
have in the southwest is

an abundance of waste material
like this, from the clay pits.

Only about 11% of what they actually
dig is clay. The rest is this. OK.

So all that is basically a waste
by-product

and we've got millions of tonnes
of this sat around.

All around the UK,
the demand for artificial reefs is

growing, in an effort to
recover our coastal biodiversity

and to protect our shores
and infrastructure from erosion.

It's early morning in Torbay,
and we are taking reef cubes

out into the bay to help
restore the reef.

Getting these 500kg
cubes to the bottom of the sea is

a team effort.

I've never operated a crane.
I just want to make that clear.

So you'll be looking at Tom
in the wheelhouse.

Tom will give you the thumbs up

when he's happy for you to lower it
away. When he's happy,

make sure Sam's happy... Gosh,
so much to think about.

..and when Sam's happy,
push the lever.

What if I'm not happy?

OK, do it.

All right, let's go down for a
minute.

Down on the wire. Down a bit.

Whoa. Stop? Stop.

The cable lowers the block
to about 15 metres.

Happy? Yeah.

Right, we'll put it...put it away

and then we can do the last bit
down...

It's on the bottom,
but is it where we wanted it to be?

We're launching a robotic camera sub
to check on the final

position of the cube.

There she is!

How long before life starts to make
this their new home?

So the fish have already
arrived on site,

so by the evening, you'd expect
crustaceans to move in.

In less than 24 hours, crustaceans
will move in? Yeah.

That's extraordinary.

So this is the before?

This is the before,
let's go now and look at the after.

Ones that have been down
a couple of years.

By providing these ready-made
reef structures,

the team are bringing
the bay back to life.

Me and James did the surveys
pre-installation and it was just a

barren seabed, cos it's sort of been
decimated by industrial fishing.

But now we've actually created
a reef here and so far,

we've identified over 160 species.

You're jok... 160 species?

Yeah, 160 species.

The reef cubes not only provide
a home for wildlife, like lobsters

and velvet swimming crabs,

they're also being used to protect
offshore wind farms.

They could replace the millions
of tonnes of carbon-intensive

granite and concrete currently used
to protect the turbine

structures
and cables on the seafloor.

Look at you, you cannot
take your eyes off the screen.

As a biologist, is this just
unbelievable to you? It's amazing.

I came up towards the end of last
year and I was saying,

it's the best UK dive I've ever
done, you know? Aw.

I've probably got about just
under 3,000 dives.

Thanks to the team's ingenuity,

marine life here is bouncing back
remarkably quickly,

and the bay will be better protected
from increasing weather extremes.

The need to protect our coasts
from intensifying storm surges has

become so urgent that in Florida,

the Department of Defense is now
funding a new generation of

artificial reefs, built to withstand
even the mightiest of hurricanes.

Florida's 360-mile barrier reef
system has lost

a staggering 98% of its coral cover,

and with it, its ability to
act as a crucial storm break.

In 2018, Hurricane Michael hit
Florida's coastline

and powered straight through
Tyndall Air Force Base,

causing $5 billion worth of damage.

A healthy reef can
absorb 97% of a wave's energy.

With Florida's coastal
infrastructure now

so exposed to the full
force of storms,

a team at the University of Miami
has been tasked with engineering

rapid response reefs, for use by the
American military around the world.

So this is the only facility
in the world that's able to generate

category five hurricane force winds,
which is 150mph

and higher, and at that point,
really, the damage is catastrophic.

This 23-metre long tank
allows Andrew

and the team to test how man-made
reefs can reduce storm damage.

If you look upstream of the two reef
lines, you can see that there's a

lot of turbulence and stormy
conditions, but as you move over

the first reef line, and especially
over the second,

you've got much calmer conditions.

Like reef cubes,

the design has an artificial base to
dissipate wave energy.

But here, the innovation is a living
top layer of larval corals,

each bio-printed into a sealed
capsule.

What we are trying to do is to make
sure that every single

one of those baby corals has
the best chance of surviving.

And the way we're doing that is to
give each one of them

a sort of a life support
system that has

all of the ingredients that they
need in it for survival.

The capsules are made
out of seaweed gel,

each containing a single coral
larva that was cultured

in a spawning system provided
by Jamie and the team in London.

It also contains beneficial
bacteria, probiotics,

and millions of heat-tolerant
micro-algae.

This is brand-new. We've never tried
this before.

I mean, in theory it should work,

but there's often a big
gap between in theory and practice.

After the first critical few weeks,
the capsule will dissolve

and the coral will continue
to grow naturally.

A machine like this could produce
thousands of coral-containing

capsules every hour.

And that's really where the
key to the restoration of coral

reefs is going to be in the future,
is scaling up,

making it cheap,
making it fast and making it easy.

Those themes of accessibility

and scalability are what make the
project in the Maldives so exciting.

The big day dawns,

when we release the IVF larvae onto
the damaged reef, and use

Steve's soundtrack to trick it into
settling where it's needed most.

Inside this bag are those
hundreds of thousands of larvae

that are the result of everyone's
hard work, and this next

couple of hours is the crucial bit,

to find out if this is going to
work.

It's worth remembering that in
almost eight years, this reef

has struggled to recover naturally
from the last bleaching event.

This is a mammoth task and starts
with some old-fashioned muscle.

What we're planning to do now is to
gently pull up the larval pool,

let all the sea water drain
out of the fine mesh at the side

and retain the larvae.

Very slowly.

It's taken almost an hour to
get to this stage.

It's physically hard
and no-one wants to be the one

responsible for dropping the net and
releasing all that precious cargo.

Perfect.

The smell is quite extraordinary.

Like Billingsgate Fish Market.

THEY CHEER

OK, we'll have one bucket.

Good work. Go, team! Woo!

The larvae are safely onboard,
and very much alive!

Yay!

This brown sediment
in the bottom of these black tubs

doesn't look like anything,
but it's frighteningly important

and the result of
so much hard graft.

It's not surprising everyone's
celebrating like it's

New Year's Eve.

In the wild, most, if not all, of
these larvae would already be dead

but because of the intervention,
almost all have survived.

We've already massively
cheated the odds.

Rather than a smattering of larvae
lost in a massive ocean, we now

have over half a million ready to be
deployed in specific sites.

The corals are getting to a point
where they need to settle,

and if they settle in the tubs,
they'll die.

So we're in a race against time.

We are now. So we want to get these
larvae onto the reef.

A mistake at this stage could be
fatal to the larvae,

and the project.

We are so close.

This is the grand moment.

The hours of sweat and graft
is coming to fruition right now.

We'll be giving those coral
larvae the acoustic

experience of being on one of the
healthiest reefs in the atoll.

So as those larvae are seeking
homes, they're

moving around the reef
trying to work out where to settle,

they're going to think that they're
on an absolute belter of a reef.

The speakers are put in place,
where they'll play

continuously for 12 hours.

There's one critical process left.

We need to drop the larvae
into precisely the right places

and for that we need an AI remotely
operated vehicle, or ROV.

So, Serena, this remarkable bit of
technology

is very much your baby, right?
Absolutely.

This is Bree. That's her name.

Bree is loaded up with larvae.

She's far more accurate
and efficient at delivery than

we humans can be.

She's trained to identify the types
of places where coral larvae

will survive best and artificial
intelligence allows her to

learn as she goes.

What is it that the camera and the

AI is going to actually be
looking for?

So it's looking for nice,
like, rocky, solid substrates,

and it turns off when it sees algae
on the substrate because

if the coral lands there,
they will just eventually die.

It's a very fine estate agent
looking for the very best

of neighbourhoods. Exactly.

The ROV can cover huge
areas of reef,

targeting the perfect spots
and never wasting larvae.

Well, this is such a complex
operation,

so many moving parts,
and trying to communicate

when half of you are under water
is just about impossible,

but it looks like somehow it's
all coming together.

Ah, that was brilliant.

Did you see how all the fish...

Did you see how all the fish
just gathered

round as soon as the sound
system turned up?

So they know it's a party. Yeah.

At last, all of Peter's larvae is
out in the ocean,

hopefully spiralling downwards
towards Steve's fish songs.

Well, guys,
that was a chaotic few hours.

Proper science in action, wasn't it?
Yeah. Yeah.

I can't believe we've actually
pulled off that plan for the day.

I think we're really onto
something.

Peter and Steve are jubilant.

We know Peter's coral IVF works,
and he and the team have

successfully reared and released
over half a million larvae here.

We know Steve's acoustic
method works.

He's controlled larval
settlement in lab experiments,

and now we've seen it work
in the ocean under real conditions.

The results we're hoping for -
new corals growing on the reef -

won't be visible for many months,
but as a result of this

extraordinary experience,
Peter and Steve are confident

that their hybrid method could be
the key to boost reef recovery,

not just here, but on damaged
reefs around the world.

This new technique couldn't have
come at a better time.

We're running
out of corals on the planet.

They're not replacing themselves
naturally fast enough.

They don't have time to
recover before the next major

bleaching event or the next
major storm event.

I think in the short-term,
this is such a crucial part of the

challenge, that we find all of these
interventions that allow us,

as soon as we've got a problem,

to get in and try to repair
some of the damage.

Peter and Steve are taking
their ground-breaking, scalable

and speedy restoration method,
and they're running as fast

and as far as they can with it.

THEY CHEER

In eight months, Australia's
Great Barrier Reef will spawn.

Peter and Steve and the coral
rescue team will be there,

ready and waiting.

In the meantime, we've got to be
tackling climate change.

This is buying us time.

It's kind of firefighting
while we try

and work out how we get to that much
more harmonious relationship

with the planet, which
I hope will be in this century.

I really do.

Without this collaborative
rescue effort,

the areas of this reef that have
lain dead and crumbling

for the last eight years may have
remained silent and still.

Now there could be thousands of new
corals growing on that reef.

We know that corals attract fish
and, in turn,

fish will call more corals in.

Now, nature takes over.

We've witnessed what becomes
possible

when we share expertise
and work together for a common goal.

We'll be back in years to come,

to check on the progress
of this reef...

..and the ongoing work of these
extraordinary scientists.