03x08 - Blind Cavefish, Coral Reefs, Bottom-dwelling Sharks

[bunniefuu]

[bright music]

- [Narrator] Coming up next on
"Jonathan Bird's Blue World,"

Jonathan explores the world of coral reefs

from the Caribbean to Australia.

Next, he goes in search

of mysterious bottom dwelling sharks.

But first, he goes deep
underground looking for a rare

and elusive blind cave
fish in the Yucatan.

All of this today on
"Jonathan Bird's Blue World."

Meet Jonathan Bird.

[water splashing]

[bright music]

One of the world's top underwater
nature cinematographers.

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Traveling the world on assignment

for all the major networks,

he is an Emmy Award-winning authority

on the underwater world.

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In freshwater or salt,
reefs, wrecks or caves,

Jonathan documents the
world beneath the waves.

[bright music]

Welcome to the Blue World.

[water burbling]

[gentle music]

- From the highest mountains
to the depths of the ocean,

life exists in nearly
every environment on earth.

But some of these
environments are surprising.

Deep beneath the floor of this jungle

lives a creature uniquely
adapted for survival

in a harsh aquatic environment.

To find it, I've traveled
to the Riviera Maya

in Mexico's Yucatan Peninsula.

The Yucatan is full of
underwater cave systems.

My quarry is the blind cave fish,

an animal that lives in the complete

and total darkness of
caves for its entire life.

To begin my quest, I head
on over to Yucatek Divers

in Playa del Carmen, where
I meet Christine Lowe,

who will be my guide to search

for this exceptionally rare fish.

[upbeat music]

We load the van in the early morning,

because we have a long drive

to a remote cenote in the jungle.

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Our travels take us over
rough dirt roads for miles.

Finally, we arrive at
the entrance to the cave

deep in the jungle.

Christine is a cave diving
instructor, someone who knows

how to keep me outta
trouble in a dangerous cave.

We discuss our plan for the dive

as we walk over to check out the entrance.

It might not look like much,
but this sliver of clear water

leads into a vast cave
system called pet cemetery.

I really don't wanna know
why they call it that.

Christine shows me on a map
that we will only be seeing

a tiny fraction of this massive system.

Hopefully we can find the cave fish.

- And actually you already
see the line going around.

It's forming a loop, and
this is where we are heading.

We will go counterclockwise,
because in that area,

very likely we are going
to see the cave fish.

- I pay special attention
to Christine's briefing,

diving in caves is serious business.

[upbeat music]

Next, it's time to suit up.

Christine wears massive
double tanks for cave diving,

so she has extra air just in case.

This is cave diving protocol.

[upbeat music]

[buckle clips clicking]

We climb down a convenient set of steps

and into the warm clear
water of the cenote,

the name for the opening to
an underwater cave system

that flows deep beneath the jungle above.

[upbeat music]

I grab my camera, do a few
last checks, fire up my lights,

and follow Christine into the darkness.

[oxygen tank hissing]

[water burbling]

Just inside the entrance,
we're already surrounded

by beautiful sculptures of rock.

I'm always astonished
by the incredible beauty

of cave formations.

During the last ice age when
sea levels were much lower,

the water table was also lower.

This cave was bone dry,
but the constant dripping

of water from the ceiling
formed thousands of stalactites.

They look like icicles and
form nearly the same way,

except out of calcium
carbonate, a kind of soft stone.

They're incredibly delicate.

If I bump them, they will
break and never grow back.

Moving slowly and carefully
is my responsibility.

Christine and I use a special kind of kick

called a frog kick.

Instead of kicking our fins up and down

like we do in the ocean,

here we gently skull them out to the side.

This keeps from disturbing
the silty sediment

on the floor of the cave.

This fine sediment is easy to kick up,

and it will absolutely
destroy the visibility.

If we can't see, it's a lot
harder to find our way out.

Divers come here often

and these fish from the
well-lit cenote outside

have learned to follow divers
lights into the darkness

to hunt in the cave.

It definitely poses a threat

to pristine and fragile cave ecosystems.

With our little hitchhikers in tow,

we finally reach the part of the cave

where Christine has seen
the cave fish before.

Now she's carefully poking
around looking for one.

[gentle music]

Since I've never seen one,

I'm not exactly sure what to look for.

I'm surprised to see
what looks like a bush

growing in the pitch darkness of the cave,

but it's actually the roots of a tree

living in the jungle up above.

The trees up there have no
problem getting plenty of water.

[gentle music]
[water burbling]

Christine is hunting in
the tangled maze of roots.

Sometimes the cave fish hide in there.

[gentle music]

[water burbling]

I can't help but notice that
there's air above my head.

This cave actually has some
very large air pockets.

Since they're connected to the
surface through tiny cracks,

the air is safe to breathe.

So I stick my head up
and take a look around.

There are more stalactites above water,

because these are in air,
they're still growing.

[gentle music]

On the bottom, Christine
points out some extremely thin

and fragile flakes of calcium.

This forms as a film on
the surface of the water

below dripping stalactites.

When it gets thick enough,
it sinks to the bottom.

In some places, the flakes are stacked up

several inches thick.

[gentle music]

This little pile is
hundreds of years worth.

[gentle music]

As I continue looking for the cave fish,

I stumbled across a jawbone
from some kind of animal

that walked in here and
died a long time ago

when it was dry.

[gentle music]

This has to be thousands of years old,

but it's in amazingly good condition.

[gentle music]

Skittering across the
sand, I find a cave shrimp.

This species is not blind,
but moves between the dark

and the light portions of the cave.

It probably feeds on organic material

that originates with the tree roots.

Life is tough in the darkness.

This is a catfish that
couldn't find its way out.

Christine searches for
another massive tree roots

that might harbor a cave fish.

When we find one, I start
looking carefully in the roots.

[gentle music]

At last, I spotted a pinkish
white fish hiding in there.

It's great to see,

but impossible to film
in that tangled mess.

Fortunately for me, the
fish shies away from light

and swims out of the roots.

Even though this species
of fish has evolved

for thousands of years in
the complete absence of light

and has no eyes, it can still
detect the presence of light

through its albino skin using
a gland in its head, why?

This fish's only defense is darkness.

[gentle music]

If it wanders out of the
dark part of the cave,

other fish can see it,
but it won't see them.

The blind cave fish
needs to stay in the dark

where it's safe.

My lights make the cave fish
swim for cover and safety.

The fish that follow me
into the cave from outside

take an interest in the cave
fish, I have to shoo them away.

[gentle music]

In fact, in the cave ecosystem,

this little fish is the top predator,

the great white shark,
if you will, of the cave.

[gentle music]

With our mission complete,
it's time for Christine and I

to turn around and head
back out to the light.

[gentle music]

Christine knows this cave
like the back of her hand,

but for added safety, we follow a line.

On the line are little
plastic triangular arrows

that point the way out.

We could use these in complete
darkness by feeling them

and holding onto the line the whole way.

Christine stops to point out
an amazing type of stalactite.

Unlike most stalactites,
which look more like icicles,

these unique formations
look like elephants feet

with bulbs instead of points on the end.

They're formed when the cave
is partially filled with water

and the stalactite grows from above,

eventually reaching the water.

Once the stalactite touches
the water, it flattens out.

As the water level changes,
bulbs form at different levels.

Finally, we're nearing the cenote entrance

and we head back into the light.

Christine explores the
cenote just under the surface

before we head back to the
steps to get out of the water.

[gentle music]

Wow, that is such a beautiful cenote.

Ugh, all the formations
hanging down and everything,

that's great.

It's hard to believe that
there's an entire world

living under the jungle
in a submerged cave,

but life survives everywhere
in the blue world,

even in complete darkness.

[bright music]

- [Narrator] Next on
"Jonathan Bird's Blue World,"

weird sharks that live on the ocean floor.

But first, the incredible
splendor of coral reefs.

[gentle music]

- [Jonathan] Coral reefs
are one of the most

important inhabitants of
shallow tropical oceans.

A coral reef may look like
a bunch of colorful rocks

or perhaps some unusual looking plants,

but it's actually a
strange primitive animal.

[gentle music]

Each coral animal called a polyp

is only about the size of a pearl.

It's little more than a mouth
with some tentacles around it.

The tentacles are used
to catch plankton to eat.

Coral is closely related

to another tentacle-equipped
animal, the jelly.

[gentle music]

If you can imagine a small jelly

stuck to the bottom that can't
swim, that's a coral polyp.

But unlike jellies, coral
polyps grow together in colonies

called a coral head.

This coral head has
several hundred polyps,

A bigger one has thousands.

Beneath the living skin of the coral

is a skeleton made of calcium carbonate.

A dead piece of coral
is heavy like a rock,

because the calcium carbonate
is limestone, a type of rock.

This heavy limestone
base anchors the colony,

so waves and storms
can't move coral reefs.

The creation of limestone is slow.

It takes hundreds of
years for a coral head

to reach the size of this brain coral.

And in spite of the fact
that it looks like a brain,

coral has no brain or eyes.

Some corals are not hard as a rock.

There are many species of soft corals.

Some look like bushes or fans.

These are often called
gorgonian sea whips or sea fans.

Others look like pastel works of art.

Soft corals grow anchored to the bottom

and look to most people like plants.

But up close, you can
see the coral polyps.

[gentle music]

Instead of a hard skeleton,

these soft corals have tiny splinters

of calcium carbonate
inside called spicules.

They allow the coral to bend
and flex with the waves.

When many coral colonies grow together,

the result is a reef.

It's a living, growing
structure that provides nooks

and crannies for everything
from invertebrates to fish.

A reef is like the buildings in a city

providing housing and protection
for thousands of animals.

When a reef forms, it creates
new habitat for other animals.

Maybe it starts out as
just a small coral head

with only space for a few fish.

But as it grows over many years,

more and more marine
life flocks to the reef

until it's a thriving metropolis.

Of course, all those small
fish living around the reef

attract larger fish
like jacks, barracudas,

and even sharks looking for a meal.

[gentle music]

The reef provides a foothold
for algae and sponges.

And that in turn attracts sea
turtles to eat the sponges.

[gentle music]

[turtle munching]

And it all starts with
just one tiny coral colony.

So much life in the tropical
oceans depends on coral reefs.

Coral reefs can grow quite large.

The largest one in the world
is the Great Barrier Reef

of northeastern Australia,
which is over 1,500 miles long.

It's so big, it can be seen from space.

Coral reefs live all around
the world in tropical waters.

They can't live in cold water,
because the coral is unable

to create calcium carbonate
if the water gets too cold.

Unfortunately, there's not much
plankton in tropical water.

That's why it's so nice and clear.

[gentle music]

But at night, plankton comes
up from cooler, deeper water,

and that's when the coral feeds.

Unfortunately, most of the time,

coral still doesn't catch
enough plankton to survive,

so it has worked out a great partnership.

Many corals have a
greenish or brownish color

because they have tiny microscopic algae

called zooxanthellae living in their skin.

The zooxanthellae make
energy from the sun's rays.

In exchange for having
a nice place to live

in the skin of the coral,

they share some of their
energy with the coral,

so the coral is partially solar powered.

As long as they grow in
nice shallow sunlit water,

solar powered corals don't
need to catch much plankton.

This is why reefs form in shallow water.

Sometimes I see coral that's turning white

as if it's losing its color.

This is called bleaching.

When corals are subjected
to environmental stress,

such as high or low water temperatures,

changes in salinity or pH, siltation,

or even just too much sun
from a really low tide,

they start to turn white.

This happens because the
zooxanthellae starts to die.

Since corals get their color
from the zooxanthellae,

when the zooxanthellae goes
away, so does the color.

And if it goes on for
too long, the coral dies,

because it needs the energy
from the zooxanthellae.

Since most coral is as hard as a rock,

very few animals can actually eat it,

but a few can.

The crown of thorn sea star dines

on the outer skin of the coral.

An outbreak of crown of thorn sea stars

can wreak havoc on a reef.

All that remains of the coral

after a crown of thorn's attack
is a dead white skeleton.

Parrot fish eat coral too.

They take big crunchy
bites out of the reef,

and grind up the calcium
carbonate as they chew.

[fish chomps]

The parrot fish have a tough beak

that's as hard as steel
for biting the reef.

And the hard particles
that they excrete later

end up as sand on the beach.

It's true, tropical beaches
are made partly of fish poop.

[gentle music]

So the next time you're
relaxing on a tropical beach

or snorkeling in shallow
water looking at the fish,

you have coral to thank.

It's a very simple animal
that can't walk or swim,

can't see, and has no brain,

but nearly all life in
shallow tropical oceans

depends on coral reefs.

[bright music]

- [Narrator] Don't go away.

Jonathan is about to find

one of the world's weirdest predators.

- This is a fearsome predator.

It looks like a blob or
perhaps an algae covered rock,

but it's a shark blending
into the sea floor

waiting for small fish to
come within striking range.

The shark is called a wobbegong,

and I've come all the way to Australia

to find this unusual fish.

It's a beautiful morning
in the Gold Coast region

of Southern Queensland, Australia,

and Palm Beach Dive Center

is putting their boat in the water.

I load my gear while the
crew prepares scuba tanks.

The dive master is my
good friend Glen Holmes,

who grew up here.

I met him 10 years ago in the Caribbean,

and he promised that if I
flew all the way to Australia,

he would show me some
very cool wobbegongs.

So here I am.

[boat engine rumbling]

We pull away from the
dock and head out to sea.

We're heading out to a dive
site called Julian Rocks

in search of wobbegongs.

Captain Herb is driving the boat,

and we have about an hour to get there.

[boat engine rumbling]

We arrive at a small, desolate island,

barely more than a rock,
and start getting ready.

[water sloshing]

Glen has been diving here for 20 years,

and he knows where the sharks are.

I suit up and prepare
myself for the chilly water.

[laughs] Yeah, I might want that.

Well, let's go see if
I can find a wobbegong.

[water splashing]

I go over the side and follow Glen

as we search for wobbegongs.

This region is right at
the edge of the tropics,

so there isn't much coral.

The bottom is covered
mostly in seaweed and rocks.

Under an overhang, I find
my first wobbegong shark.

It's a big, ornate wobbegong,
almost as long as me.

wobbegong sharks have adapted

to live camouflaged on the
bottom, rarely moving a muscle

until a meal-sized fish comes into range.

It's called an ambush predator
because it waits for the prey

to come within striking
range and then lunges for it,

rather than trying to chase prey around.

If any of those fish above
its head get too close,

they'll get gulped down.

Nearby, a spotted wobbegong
tries to get comfortable.

Even though there are
millions of tiny silver fish

swarming above its head,
this wobbegong isn't feeding,

it's stuffed.

Every wobbegong here has
been gorging itself for days,

they can barely move.

Moving out into deeper water,

I find several sand tiger sharks,

often called gray nurse
sharks in Australia.

These sharks look and act a
lot more like a typical shark.

They let me get pretty
close for some pictures.

Not long ago, people thought
all sharks had to keep swimming

like the sand tiger to keep
water moving over their gills.

For some species like the
hammerhead, this is true.

[gentle music]

Hammerheads must keep
swimming at all times,

or they'll drown.

They never rest on the bottom.

But many species of sharks
sometimes stop swimming

and rest on the bottom.

[gentle music]

Here, a lemon shark is
taking a break on the sand,

gulping water through its
mouth to ventilate its gills.

[gentle music]

Here's a pair of nurse sharks
common in the Caribbean,

also resting on the sand.

They're not in the mood to socialize.

As I approach, they swim off.

[water sloshing]

Wobbegongs on the other hand

spend their entire lives on the bottom,

patiently waiting for prey.

They very rarely swim, because
it gives away their position.

Although there are more
than 400 species of sharks,

you might be surprised to learn
that a large number of them

look nothing like the typical
predator most of us associate

with sharks like these
Caribbean reef sharks.

Of course, the wobbegong looks
nothing like a reef shark.

And neither does the saw shark,

another odd looking bottom dweller

that appears more like a stingray

with a long toothed blade on its head.

It swings the blade back and
forth in a school of fish

to catch dinner.

In 2006, a new species
of bottom dwelling shark

was discovered in Indonesia.

It belongs to a group of
sharks called epaulette sharks.

What made this one different is the fact

that it actually walks along
the bottom on its fins,

so they called it the walking shark.

Cameraman Pierre and I charter

a traditional Indonesian pinisi

and set off to a remote
region of Indonesia

to find this elusive shark.

[boat engine rumbling]

As the sun sets, we
board the inflatable boat

and head to the dive site.

[boat engine rumbling]

I've come to a remote
reef in Papua, Indonesia

to find a really weird shark.

[water splashing]

The walking shark is
usually only found at night.

So Pierre and I search the
reef in the dark after sunset.

It takes a while, but
we find a little shark.

[gentle music]

It doesn't like our lights at all,

and getting any decent shots
of it proves difficult,

but you can see how it walks on its fins.

[gentle music]

It is not exactly a fearsome predator.

This little shark hides
from us in the reef.

[gentle music]

The next day, I suit up and roll off

the inflatable boat again.

[water splashing]

This time, we're searching the
reef for another wobbegong.

The most common wobbegong
on Indonesian reefs

is called the tasselled wobbegong.

Its tassels located around
the edge of its head,

allow it to blend into
the bottom really well

by disguising its shape.

On a typical reef, this
shark blends right in.

It's very confident in its camouflage

and won't move even if I get really close.

The wobbegong has a
clever way of breathing.

Instead of gulping water
in through its mouth,

it has a set of spiracles,
almost like nostrils,

right in front of the gills.

Water goes in through the spiracles,

then back out through the gills.

It's an adaptation for a shark

that spends a lot of
time flat on the bottom.

So sharks are a diverse group of animals,

and they don't all look the same.

The saw shark, walking shark,
and wobbegong are all examples

of the amazing kinds of
bottom dwelling sharks.

[bright music]

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