All language subtitles for NOVA.S48E07.Reef.Rescue.1080p.x265-ZMNT_track3_[eng]

♪

♪

NARRATOR:
Coral reefs have captured
the human imagination

for as long as we have
ventured beneath the waves.

ALANNAH VELLACOTT:
Towering, romantic, strong,
resilient,

but very ornate and,
and delicate at the same time.

There really is
nothing else like it.

NARRATOR:
Beyond their beauty
and brilliance,

coral reefs support
a quarter of all marine life

and are crucial for ocean health

and human survival.

But now these precious creatures

are in crisis,

as ocean heat waves
are bleaching corals

of all color and life.

♪

By the end of this century,
coral reefs could be lost.

RUTH GATES:
Can we help them?

Can we accelerate
natural selection?

Can we accelerate
adaptive rates?

♪

NARRATOR:
On tropical reefs around
the globe,

scientists are fighting
a desperate race against time.

♪

Unlocking the secrets of
millions of years

of coral evolution

and trying to speed it up.

JULIA BAUM:
If we are going to save
coral reefs,

we have to start intervening.

NARRATOR:
Their ideas are new
and experimental.

And for the first time,
their daring research

will be put to the test.

GATES:
I think science and scientists

are being asked to
solve problems.

ANDREW BAKER:
Honestly, we don't know

whether it's going to work.

The risk of doing nothing
is the risk of

risking every reef
on the planet.

NARRATOR:
"Reef Rescue,"
right now on "NOVA."

♪

♪

GATES:
I will often describe it as
my cathedral.

If you could imagine a cathedral

with all of the
stained-glass windows,

all of that color is
splashed across the landscape,

with the fish
darting in and out.

It's the place I go
where I feel awed

by the complexity of
the architecture around me.

GREG ASNER:
Coral reefs have been compared

to tropical rainforests,
and what I mean by that is

the diversity of the species and
how they're packed in together,

how they create
this kaleidoscope

of color and function.

VELLACOTT:
When I go underwater,

each coral head
is like its own little city.

When you get to a
massive spur and groove system,

it's like downtown Atlanta,

super busy, bustling,

characters everywhere,
different sounds,

clicking and popping
and bubbling.

And it reminds you

that we are all one piece of
a community, or ecosystem.

NARRATOR:
Corals appeared
500 million years ago.

They may look like rocks,
but corals are in fact animals.

Each tiny coral creature

is called a polyp.

The polyp is essentially
a mouth with tentacles

used to trap floating food,

but most corals also have
another source of nourishment.

GATES:
Inside the cells of the animal,

there is a tiny plant cell
and they, as all plants do,

are able to use the
energy of the sun, capture it,

to combine carbon dioxide
and water

into a small food molecule
and oxygen.

NARRATOR:
These microscopic plant-like
organisms are algae.

The algae feed the coral animal,

and the coral
gives the algae a home.

It's a dynamic
symbiotic relationship.

So much so that
the algae are called symbionts.

♪

Reefs begin when coral polyps

secrete a thin layer of
calcium carbonate

to create a skeleton.

Hundreds and hundreds
of identical coral polyps

create a colony.

And over thousands of years
of growth,

coral colonies build the reef.

So animal, vegetable, mineral.

That is what a coral is.

NARRATOR:
Christmas Island is an atoll

in the Pacific Ocean
made entirely of coral.

Julia Baum is a
Canadian marine biologist.

For more than a decade,

she's studied the reef's
unique ecosystem

and the threats it faces.

It always feels great
to be back.

It's a bit of a mix of emotions;

there's, there's so much
invested in every single trip.

Always a little bit of
excitement

about an adventure
that's about to begin,

and also maybe
a little apprehension

just to make sure,

is everything going to go okay?

Hey!

(laughs)
Hi!

I think that it's actually,
I know it sounds crazy...

And then I think that...

but I think it's actually
you're gonna,

you're gonna drop there.

MAN:
And that's...

NARRATOR:
It's Julia's first day out on
the reef this year.

Oh, did you...

NARRATOR:
The team dives down to
take stock of the coral.

(splashing)

♪

BAUM:
When I first started doing
research on the ocean,

I had been so focused on
sharks and fish,

and at some point,

I think I kind of looked down
and saw the coral and realized,

"Hey, the coral
are the whole foundation

of this ecosystem."

And if we're worried
about this ecosystem,

we really have to be worried
about the coral themselves.

We have hundreds of corals

tagged all around the island,

and we take tiny tissue samples
from them.

We can take the photos

to identify individual
coral colonies themselves

and get a sense of who's there
in the community.

A brain coral is one of

the main types of corals
that we've been working with.

There's also branching corals
and flat corals,

so lots of different shapes,

and those are important
because they provide

different types of habitat
for fishes.

NARRATOR:
Each year, Julia and her team
meticulously tag,

sample, and photograph
40 plots of coral,

building a timeline of
how the reefs are changing.

During the
2015 and 2016 El Niño,

water temperatures here

increased by
four degrees Fahrenheit.

The heat set itself down
on this island

and just got a chokehold on it,

and it just kept going and going
for ten straight months.

And what we saw was
a complete ecological meltdown.

By the time we came back

in March 2016,
almost everything was dead.

It was like a graveyard.

It's just hard to believe that
a whole island can die

in less than a year.

(diver panting)

SCIENTIST:
How'd it go? Okay?

Tough, a lot of stuff
going on there.

I want to look at
both of those dive slates

and compare the corals,

photo for all of them,

tissue for all of them,
and growth for some of them.

Yeah.
Okay.

BAUM (voiceover):
It's pretty devastating,
being down there,

because I just remember
that being my favorite site,

and it just feels,
like, how did this happen?

And even though, obviously,

intellectually
I know exactly what happened,

but emotionally
it still feels like...

it's just really, um...
it's a pretty sad remnant

of what it was.

It's gone, really.

NARRATOR:
Tropical reefs around the globe
were severely impacted

by the deadly ocean heatwave.

And scientists have been
mobilizing...

led by the Hawaii Institute
of Marine Biology...

a research station
perched on an island

surrounded by coral reef.

Guiding this enormous effort

is visionary scientist
Ruth Gates.

(laughing)

You have a couple of options:

you move, you adapt, or you die.

Obviously corals are dying,
they can't move,

so their only option is
to adapt.

NARRATOR:
Corals have a natural ability

to adapt to changes
in their environment

and have done so
for millions of years.

But now,

the oceans
are heating up too fast.

GATES:
So, can we help them?

Can we accelerate
natural selection?

Can we accelerate
adaptive rates?

NARRATOR:
Ruth is a revolutionary thinker

in a new area of coral science.

It's called assisted evolution.

GATES:
It is our responsibility to
take our science

and activate things
that can make a difference,

try to solve the problem

instead of just
describe that it exists.

♪

NARRATOR:
And to take a closer look at
the problems corals are facing,

researchers use
a powerful laser microscope

to generate
images of living corals.

(machinery whirs)

(lens winding)

Fluorescence highlights
the algae partners in red.

This is a most beautiful coral.

It's completely healthy,
it's showing,

it's extending its polyps
away from the skeleton.

Kind of out there, waving.

It's just dynamic and beautiful.

Each polyp looks like it's got
a different personality

and it's blowing me a kiss.

It's this one
that's blowing me a kiss.

(laughs)

(microscope lens winding)

NARRATOR:
But what happens to
the symbiotic algae

when waters warm?

GATES:
This is actually a
partially bleached coral.

It's starting to
lose its symbionts.

You can see
there's a lot more black space

in between the corals.

NARRATOR:
When heat stresses the corals,

they expel their algae.

These dots of red are
the plant cells

that the animal has
essentially spat out.

They're no longer
serving the animal.

It's no longer moving
anywhere near as dynamically.

It's kind of gone very quiet.

NARRATOR:
Without the algae,

corals lose their color.

And this is coral bleaching.

(waves lapping)

(birds chirping)

NARRATOR:
Alannah Vellacott is a diver

and coral restoration specialist

who understands this problem
firsthand.

They can always use
a bit of fanning.

Oh, sorry, buddy.

I keep knocking you.

NARRATOR:
Alannah works at Coral Vita,

a coral farm in the Bahamas
that grows corals

to revitalize dying reefs.

VELLACOTT:
Currently, 80 percent of corals

are dead in the Caribbean.

That is especially sad
and especially troubling

because we cannot afford
to lose our coral reefs.

NARRATOR:
Reefs are highly diverse
ecosystems.

Fish shelter, find food,
and rear their young

in their many
nooks and crannies.

Fewer reefs means fewer fish,

but it's not just the marine
ecosystem that's at risk.

People depend on reefs for
food and income.

(fishing reel winding)

VELLACOTT:
Bahamians are very intimately

tied to our waters,
because it is our livelihood.

Whether you work in a hotel,

whether you're a dive operator,

whether you're a fisherman,

whether you just enjoy
having a conch snack

at the end of the day,

we all depend on these
coral reefs.

If the world continues

to go in the direction
that it's going in,

ignoring what our reefs are
trying to tell us,

it very well is
the end of our livelihoods

here in the Bahamas.

NARRATOR:
Bahamas and beyond,

some three billion people

rely on fish as
a source of protein,

and the overall
economic value of reefs

is estimated at tens of billions
of dollars annually.

(car door closes)

Almost 90 percent of the corals

surrounding Christmas Island
bleached,

and Julia wonders if the reef

and the biodiverse habitat
it provides

could be lost.

Okay, so I have 2015 loaded.
Mm-hmm.

This is just five months before

the heat stress started to hit.

So, the reef is looking
really healthy.

So then let's load the 2017
on top of that

and take a look at
that one overlaid.

Kind of shows how much
the structure is breaking down.

Just...
All the height is eroding.

NARRATOR:
Devoid of living corals,

the reef is crumbling
and falling apart.

BAUM:
Oh, God, this is horrible.

♪

NARRATOR:
Can a damaged reef regenerate?

(bubbling)

Each year, Julia's team anchors

new clay tiles to the reef
and retrieves tiles

from previous years.

Normally, baby corals
will settle on these,

and the team will document
any signs of new growth.

BAUM:
It feels like a
waiting game to see...

is this gonna turn the corner
and recover,

or is it gonna decline and die?

(camera clicking)

I still need the white light
to look at it though.

(camera clicking)

We have a baby coral from
one of the degraded sites.

We hoped for it,
but we didn't really expect it.

So, yeah, that's exciting.

NARRATOR:
This first evidence of new life

is a tentative sign of
regeneration.

But how could this happen?

After bleaching,

researchers feared
the reef was lost.

BAUM:
In the midst of
all this devastation,

we found a glimmer of hope.

NARRATOR:
Julia discovered life
among the ruins...

baby corals struggling
to rebuild.

This meant some of the parent
corals withstood the heat.

BAUM:
The corals here had been

sitting in essentially a
hot water bath for ten months,

so they had been stressed out

more than any coral
on the planet,

and yet, here they were,
looking perfectly healthy.

NARRATOR:
Here, while water temperatures
remained high,

a small percentage of the corals
recovered,

making these the only corals
ever observed

to have been exposed to such
extreme temperatures

for so long and survive.

So, to me, this was
almost like a miracle.

What is it that's so special,
that's so unique

about these corals
that healed themselves

while they were still
under stress.

What is it about them?

NARRATOR:
Why do some corals survive
when others perish?

What is the secret of
these super corals?

And what can we learn from these
survivors to help save the rest?

(indistinct radio chatter)

MAN:
Traffic, traffic.

(indistinct radio chatter)

NARRATOR:
Greg Asner's
Airborne Observatory

is a custom-designed plane

equipped to create a picture
of how reefs are changing.

How many passes through here?

MAN (on radio):
We're going to do...

five more.

(radio chatter)

NARRATOR:
Using a spectrometer

and LiDAR lasers,

Greg can analyze the corals
from above,

measure their chemistry,
and create a 3D image.

ASNER:
This region here, in the pinks,
that's the live coral.

These corals are
all a mix of dead and live.

The system gives us a very
unique view of coral reefs,

an understanding of where
the live coral is located.

That's really critical,
especially nowadays

where we're looking
for surviving corals

in literally... in a sea of
a lot of dead coral.

Yeah, we're over
the big island now.

Like many other reefs,

they've gone through
a lot of change.

(propellers humming)

NARRATOR:
The burning of fossil fuels

has increased the concentration

of atmospheric carbon dioxide,

raising the Earth's
overall average temperature.

ASNER:
You raise the total temperature
of the planet

and you've changed literally
the fundamental heat flow

over the earth's surface.

You're causing heat waves
in the oceans.

You're causing droughts on land.

You're causing a rebalancing of
the entire thermal portfolio

or profile of
the earth's system,

and that's the thing that we're
dealing with as biologists.

NARRATOR:
These changes may have
deadly consequences.

So Greg is taking his airborne
research one step further...

teaming up with Ruth Gates

to find corals that
are resistant to bleaching.

ASNER:
We're going to be
getting in the water

to look at the corals that
we flew over yesterday.

And this is key for
linking the aircraft data

to what's going on
in the coral itself.

That's how we make
the connection.

(splashing)

NARRATOR:
Underwater, Greg will use
a small spectrometer

specifically designed
for diving.

♪

Tools in hand, Ruth and Greg
set out to find

the specific corals identified
by the airborne observatory

as survivors of heat stress.

(bubbling)

They need to confirm
that the data from the plane

reflects the reality
on the reef.

By monitoring the reef
over several years,

Ruth has already identified

corals that have
resisted bleaching.

And sure enough,

Greg's spectral
data from the air

matches Ruth's
observations underwater,

bringing them one step closer

to identifying super corals

at a scale and speed
previously unimaginable.

So, the dark brown coral

in the bucket right now,

we affectionately term
"super corals,"

and we call them that because

they are unaffected by
the conditions or the stress

that is causing other corals

immediately adjacent to them
to pale and whiten

and show signs of
very severe stress.

So once we can understand
what is different

between the super corals
and the weak corals,

our goal is to develop
or breed more super corals

that we can use to
restore damaged reefs.

♪

(water churning)

NARRATOR:
Now Ruth's team prepares

to breed the super corals

that have survived
bleaching events.

Corals here are spawning tonight

and researchers will
act as matchmakers.

GATES:
If we've got

a really good performer

over here and over here,

let's not leave it to chance

that their
eggs and sperm would meet.

Let's bring them together
and make sure they do.

So that's accelerating
a natural process,

really having
a slight human intervention

to make sure we breed
the best moving forward.

(indistinct chatter)

NARRATOR:
As night falls,

Ruth's team prepares

for one of the most phenomenal
events in all of nature.

Each coral species spawns
at a very specific moment,

timed with seasonal
temperatures and the moon.

GATES:
Corals can sense the moon,

and they will release
their eggs and sperm

within five minutes

of a particular phase
of the moon,

it's an astonishing thing.

(boat motor humming)

NARRATOR:
Once spawning begins,

it won't last long.

Researchers use red lights,

so they won't disturb
the corals' ability

to sense lunar cues.

Then move it across...

NARRATOR:
The team must work quickly

to collect
the precious sperm and eggs.

(splashing)

An entire year's work
is on the line.

♪

Corals are fixed in place,
so they release

gamete bundles containing
their egg and sperm

into the water column.

These buoyant bundles
rise towards the surface,

creating an underwater blizzard
where fertilization begins.

♪

The gametes from selected coral

are caught in the nets.

Lids secured,

researchers
head back to the boat.

Yeah, we have everything!

NARRATOR:
The team combines
the coral gametes

according to
a predetermined plan,

breeding them for
their strengths.

(bucket contents shifting)

(boat motor humming)

Time will tell if

tonight's efforts were
successful,

but past years of collecting,
breeding, and observation

have already paid off,

as lab-reared "super corals"
can tolerate

warmer temperatures.

How do we move the needle

and scale to
many different places?

Because the corals
that do well in Hawaii

don't all live, say,

in the Great Barrier Reef.

NARRATOR:
In Australia, hopes are high

that assisted evolution
could help save

one of the seven natural wonders

of the world.

The Great Barrier Reef
has been hit hard by

successive ocean heat waves,

resulting in
severely bleached coral

along its entire
1,400-mile length.

Researchers here are taking
the next big step,

moving assisted evolution
out of the lab

and into the ocean.

And there is no better place

to prepare super corals
for this journey

than in the state-of-the-art

National Sea Simulator.

Here, Ruth Gates'
long-time collaborator,

ecological geneticist
Madeleine van Oppen,

is soon to embark on
a groundbreaking trial.

MADELEINE VAN OPPEN:
Ruth and I met,

I think maybe 2005.

I think the idea
was already starting to happen

that we should use the knowledge

that we had gained
over the past decades

on how corals
adapt and acclimatize,

to actually harness
those mechanisms

to help corals evolve further.

NARRATOR:
Researchers here can set the
temperature and acidity levels

of individual aquariums
to match those predicted

for the ocean
in the years ahead.

And Madeleine is creating a new
kind of super coral:

a hybrid.

A hybrid is a cross between
two entirely different species.

VAN OPPEN:
Hybridization does
happen in nature,

in corals and also in
other plants and animals,

but it doesn't happen
frequently.

NARRATOR:
When it does, hybrids have
proven to be more resilient.

VAN OPPEN:
This is a hybrid coral
that we've actually

created in the lab in 2015,

and actually we put it through
seven months of exposure

to future ocean conditions,

so warmer
and more acidified oceans,

and it survived those
conditions.

NARRATOR:
Now that Madeleine has
achieved success

with lab-reared hybrids,
she needs to find out

if newborn hybrids can grow and
survive in real ocean waters.

♪

To create these new hybrids,

Madeleine needs eggs
from one species

and sperm from another.

There is no better time
to gather these ingredients

than when corals spawn.

VAN OPPEN:
So, this cup is full of the
bundles of eggs and sperm

that are collected outside which
I will now pour over this mesh.

And the mesh is of a size that
the sperm will go through,

and the eggs will stay on top.

NARRATOR:
With egg and sperm
from two selected

coral species separated,

Madeleine can now bring these
together to create the hybrid.

Even though we have
a fabulous sea simulator,

it still is an aquarium

and it's not exactly
the natural environment,

so we need to test
those results,

validate those results
in the field.

NARRATOR:
For the first time ever,
these babies are headed

to the Great Barrier Reef.

VAN OPPEN:
The biggest challenge is the
really high mortality

we tend to see in the field.

NARRATOR:
These lab-reared babies
have never experienced

real ocean waters before,

and the transition could
be deadly.

VAN OPPEN:
We might get a cyclone that all
of a sudden

pulls down the water,
or we might get

a lot of cloud formation
during summer

that will reduce the amount
of light.

NARRATOR:
The baby corals grow on tiles

and are transported on trays

to a designated site
alongside the reef.

VAN OPPEN:
We really need to have these

field results before
the regulators will allow us

to actually implement these
interventions

in reef restoration.

NARRATOR:
After three months,
scientists from Madeleine's lab

oversee the infant hybrids'
first checkup.

ANNIKA LAMB:
So, right now we're
cleaning the tiles,

which we just brought up
from the ocean,

so that they'll be ready
for the photographer

to get a clean shot of.

KATE QUIGLEY:
I'm just going through
each tile,

trying to find the babies,

which are still quite small,
they're kind of,

adolescents,
I guess you could say now,

about six months old,

and so we just find them,
and then I circle them,

we take a photo, and that
allows us to look at survival,

and then it also allows
us to measure growth.

NARRATOR:
There are more than
a thousand tiles

with different genetic
combinations.

It will take over a week
to examine and photograph

every one individually.

(indistinct chatter)

QUIGLEY:
So we've just taken all these
photos outside,

so now we're going to start
analyzing them,

and the first thing we do

is just look at alive or dead.

Yeah, so no...

No pencil marks on this one.

Maybe try the next one?

QUIGLEY:
I don't see anything
on that one,

some dead ones, yeah, long dead.

LAMB:
Yeah.

QUIGLEY:
A lot of dead guys.

♪

NARRATOR:
Early observations
are concerning.

Many of the baby hybrids did not
survive the journey

from lab to sea.

But hope is not lost.

There are more tiles to examine

in the week ahead.

VAN OPPEN:
Climate change has affected the
Great Barrier Reef

quite dramatically
in recent years.

We lost half
of the coral present.

As soon as populations start
to lose genetic diversity,

the capacity to adapt further
and respond

to environmental change
also diminishes.

It can become a downward spiral
very, very quickly.

GATES:
Let's think about
how we actually react

instead of just watching our
system die before our eyes

and then asking ourselves
20 years from now,

"God, I really wish
I'd done something."

♪

NARRATOR:
During the filming
of this documentary,

Ruth Gates is diagnosed
with brain cancer.

Like the coral reef she loves,
her life hangs in the balance.

♪

Laetitia Hedouin is a scientist
who studied under Ruth Gates.

On the island of Mo'orea
in French Polynesia,

Laetitia is "conditioning"

or "training" corals
to survive ocean heat waves.

Her recent graduates are growing
in this coral nursery.

HEDOUIN (speaking French):

♪

NARRATOR:
Laetitia aims to train large
quantities of corals

to make them more resilient.

So her work begins in the
crucial first hours

of a coral's life.

HEDOUIN:

NARRATOR:
Laetitia will expose these
coral embryos

to increasing amounts of
heat stress.

Like young athletes
on a treadmill,

they will be conditioned
to become "super."

NARRATOR:
The goal is to increase their

thermal tolerance by subjecting
them to an exercise regime

similar to what they may
experience

in an ocean heat wave.

HEDOUIN:

NARRATOR:
The embryos have grown quickly
into tiny larvae.

This is the only time
in a coral's life

that it will ever swim.

(rooster crowing)

HEDOUIN:

NARRATOR:
Once settled, the coral polyp
begins to grow.

Soon it should be moved
to the coral nursery

in Mo'orea's lagoon.

But now, Laetitia finds trouble
brewing on the reef.

HEDOUIN:

NARRATOR:
An impending ocean heatwave
threatens the reef,

and her research.

NARRATOR:
As the summer heat intensifies,

so do warnings from the
Intergovernmental Panel

on Climate Change.

About 1900 to present,
that basically represents

a degree Celsius of warming.

REPORTER:
With one and a half degrees,

70 to 90 percent of coral reefs
are lost,

but at two it's virtually
all of them.

It's very clear
that half a degree matters.

I think this report is alarming,

it should make us act.

IPCC and other reports now
coming out

are just getting to the level
where they're saying,

"Look, this is happening faster
and, and more extreme

than we thought."

The urgency of this cannot
be overstated.

The changes are real,
the changes are rapid,

and they can be quite extreme.

NARRATOR:
And if we lose reefs, there
will be dramatic consequences.

(waves splashing)

Coral reefs provide safe harbor
for our coastlines.

They buffer waves,
helping to prevent erosion,

property damage,
and loss of life.

So, if you look out just in
front of the horizon,

there's a line there, a line of,
of,

of waves, a line of foam,

and that is the reef crest,
and that

is our first line of defense

when it comes to storms
and hurricanes.

NARRATOR:
When natural ecosystems
that protect coastlines

are in poor condition,

people are vulnerable.

(wind whipping)

(water splashing)

When Hurricane Dorian hit,

it was the worst tropical
cyclone on record

to reach the Bahamas.

The damage was catastrophic.

VELLACOTT:
So, September last year,
the islands of Abaco

and Grand Bahama were absolutely
devastated by Hurricane Dorian.

Sixty percent of Grand Bahama
was underwater,

and thousands and thousands
of people lost their homes.

Hundreds of people are
still missing today.

My childhood home where my dad
lives was completely destroyed.

For the first time I experienced
what it was like

to be a climate change refugee.

And as much as we'd like to
think

of climate change refugees
as people of the future,

the future is today.

It's happening right now.

♪

NARRATOR:
And what happened in the Bahamas

could happen to coastal
communities anywhere.

Billions of people live within
60 miles of a coastline.

♪

The east coast of Florida is
lined with coral reefs

that have protected people
here for thousands of years.

But now,
these reefs are crumbling.

♪

The Sustain Laboratory at the
University of Miami

is one of the few places
in the world designed

to measure the impacts of a
Category 5 hurricane.

(wind whipping, water rushing)

Here, Andrew Baker and his team

are working to quantify
how corals

mitigate the impacts of
extreme storms.

Is there any wind going on this?

MAN:
Now there is,
now there is, yeah.

BAKER:
That's pretty good, it's
breaking right on the coral.

Because of climate change,
we're seeing rising seas,

we're seeing more powerful
storms,

we're seeing storm surge

and other kinds of flooding
impacts.

Coral reefs have been shown
to reduce wave energy

in some cases by 94, 95 percent.

(water flowing)

NARRATOR:
Without reefs to protect
its shoreline,

storm surges could
devastate Miami.

BAKER:
How do we make coral reefs

more climate ready,
more climate tolerant,

more thermally tolerant,

and how do we protect
our coastlines

from the damaging effects
of storms?

So, what we're trying to do
is not only use coral reefs

to build natural breakwaters,
but make the very corals

that we're using to build
those reefs

themselves more thermally
tolerant.

♪

NARRATOR:
Andrew and his team
are trying to make reefs

more climate-ready by helping
corals switch their algae

to ones that can take the heat.

The researchers use a technique
called "controlled bleaching,"

attaching the corals to a raft,

then raising them up toward
the surface

where they'll receive
more sunlight.

After a few hot days under
clear skies,

the coral stress,
eject their algae, and bleach.

And without the nourishment
the algae provide,

the corals will soon die.

But Andrew has a plan to save
them from this fate...

BAKER:
This partnership between the
coral and its algae

dates back over
a hundred million years.

We have different types of
corals,

but we also have many different
types of algae,

and in fact they can sometimes
switch from one type of alga

to another, and that's exactly
what we think

we're seeing under
climate change.

NARRATOR:
And some of these algae

are more tolerant to heat.

BAKER:
If corals are able
to flexibly associate

with different types of algae,

perhaps they could switch to
these more heat tolerant ones

and that might help
them survive.

NARRATOR:
Heat-tolerant algae
are less likely

to be expelled by the coral,

and the coral won't bleach.

If the corals bleached
on the raft recover

with heat-tolerant algae,
they may survive the next

ocean heat wave.

And this could be
a big step forward

for assisted evolution.

BAKER:
This is a test... we're hoping

that this is going to be
something that

proves successful,
that is easily scalable,

cost effective, and we can roll
it out and apply it

to the restoration efforts
that are going on

all over the place.

♪

NARRATOR:
Today, Andrew's team

plants the corals that bleached
on the raft out on the reef.

Standard corals act as
a control group.

BAKER:
We're hoping that the corals
that we've bleached

on these rafts are going
to recover with

different symbionts that we hope

are more thermally tolerant

and that help these corals
resist bleaching in the future.

NARRATOR:
The corals may now have the
ability to survive bleaching,

and the next ocean heat wave.

But what about the one
after that?

BAKER:
If climate change is
still ongoing past 2100,

then nothing we're doing
is going to help solve that.

Ultimately, we have to get

carbon emissions under control

and try to prevent
this runaway warming event.

NARRATOR:
And in the midst of this
planetary crisis,

coral scientists receive
devastating news.

At age 56, Ruth Gates, pioneer
of assisted evolution, dies.

Yeah, it's difficult to talk
about it, but, um...

(sighs)
I just, it's so hard to believe
that she's gone, right?

♪

HEDOUIN:
Ruth was a very inspiring
person.

She was always smiling

and laughing, and...
and so I think, um...

yeah, sorry.

She always find a good word

and, and the time to be here
when you need it.

(laughs)
I think that I, I've never
laughed so much, um,

doing science than I have
with Ruth Gates.

It was, we had a great time,

and to lose her,

it's like a huge piece of the,
of the science machine,

but also the leadership machine
just disappeared.

What she did do was instill
so much spirit

and motivation to keep going.

HEDOUIN:

VAN OPPEN:
We wanted to really send out
the message

that assisted evolution is an
important approach to explore,

and Ruth, of course,

played a very big role
in sending that message out

across the world and I think
we have succeeded.

We've been able to convince
the community

that this is important.

♪

NARRATOR:
When Madeleine van Oppen's team
first checked

the experimental hybrids,
the results were discouraging.

But they didn't give up.

There it is.

(laughs)
I knew it was on here, I saw it.

NARRATOR:
Tiny young corals are alive
on the tiles,

signs that these
heartier hybrids are surviving

life outside the lab,

a first for the team.

Well, we still have to take
a good look at the data,

but we're seeing corals popping
up here and there.

Is Grant gonna take it down?

They're gonna take them back out
onto the reef,

and we'll be keeping those guys
out there for another

few months until we check up on
them again in October.

♪

NARRATOR:
Back at the sea simulator,

researchers share their
documentation with Madeleine.

I see some kind of...

Yes, it looks like there's
some structure still there,

rather than the whole, isn't it?

And it's smooth texture.

QUIGLEY:
That is clean.

VAN OPPEN:
That one is quite pale,
isn't it?

Yeah.

I saw a lot of variability
in color.

When we first bred coral
recruits in the sea simulator

five years ago, everything died
between Christmas and New Year.

We had a huge effort, and then
the year after we had

a little bit longer survival,
and so we learned as we went.

These are the baby steps
that we have made,

but small steps in
the right direction.

It gives me hope and I just pray
that it's gonna be enough.

NARRATOR:
Assisted evolution is now
a growing movement

around the globe.

Scientists are finding
successful solutions

that might give corals
the chance they need

to make it through
the coming decades.

Coral Vita is expanding its
farming operations

beyond the Bahamas,
aiming to provide

resilient corals to reef rescue
operations worldwide.

We can make choices
to help our environment,

to help our coral reefs,
to bring them back to life.

♪

We are growing corals to be more
resilient to the effects

that climate change is having
on our oceans.

NARRATOR:
Super corals tested and planted
by the Gates Coral Lab

are now being used to restore
the protective reef around Oahu.

Andrew Baker's corals bleached
and recovered,

but did not switch
to the heat-tolerant algae.

However, back in the lab,

different species have
successfully made the swap

and are now being planted
on reefs off Miami to see

if these corals remain resilient
in warming ocean waters.

Julia Baum discovered that

the corals that survived
the mass bleaching

on Christmas Island did
so because

they switched to a heat-tolerant
algae naturally.

♪

Tragically,

the reefs around the island
of Mo'orea

experienced a massive
ocean heat wave.

Fifty percent of the corals
raised in the nursery perished.

But those that made it proved

their resilience and
Laetitia Hedouin is optimistic

that she will learn from
the survivors.

♪

GATES:
We need to know more, so we
can harness that knowledge.

I mean, what could be better
than that?

Being a part of a solution
that will help the world.

♪

♪

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♪