03x06 - Sea Snakes, Symbiosis and Coral Spawning

[bunniefuu]

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- [Announcer] Coming up next

on "Jonathan Bird's Blue World,"

a look at symbiosis in the ocean.

Then a mission to Bonaire
to learn how coral spawns.

[bright music]

But first, the deadliest snakes
in the world, sea snakes.

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

Meet Jonathan Bird.

[water splashes]

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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."

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[water gargles]

- The sea snake is an animal
surrounded in mystery,

known for its incredibly powerful
venom, but not much else.

Just how dangerous are
these marine reptiles?

I've traveled to Queensland, Australia,

on a quest to learn about sea snakes.

[cheerful music]

Here on Australia's Great Barrier Reef,

sea snakes are fairly common.

Let's go see if we can find one.

[water splashes]

I hit the water, grab my camera,

and head towards the sea floor.

[dreamy music]

Today I'm diving a little sea
mount called a coral balmy.

It's a mini mountain of corals
sticking up from the bottom,

but not quite reaching the surface.

Near the top of the balmy,

thousands of small fish
feed on plankton passing by

in the current, but they
stay close to the reef

because they're being watched
by a big school of jacks

who are on the prowl for food themselves.

[dreamy music]

The balmy is covered in healthy coral

that provides lots of nooks and crannies

for the fish to hide if they need cover.

[dreamy music]

On the other side of the balmy,

a large school of
snappers are also looking

for something to eat,

and keeping a safe
distance from the jacks.

[dreamy music]

As I swim along at the base of the balmy,

I'm keeping my eyes open
for a snake-like animal.

The coral looks healthy,

and a spine cheek anemone
fish gives me a quick glance

from the safety of her host anemone.

But I keep scanning the bottom,

and at last I've found my
quarry, an olive sea snake,

the most common species
around the Great Barrier Reef.

It's swimming along the bottom,

doing the same thing
everything else is doing,

looking for food.

The sea snake is closely
related to a land snake,

except it's adapted for life underwater.

[dreamy music]

When a sea snake flicks its tongue,

it's getting rid of excess salt secreted

by special glands in its mouth.

Sea snakes live exclusively in the ocean,

but since they're reptiles,

their kidneys can't deal
with too much excess salt

in their blood.

A sea snake gets around
with a flattened section

of tail that looks like an
ore and serves as a fin.

It looks just like an eel when it swims,

undulating its body and getting propulsion

from that flattened tail.

[dreamy music]

Although seas, snakes prefer
to eat eels, shrimps, and fish,

these snappers aren't at
all afraid of the sea snake

because they're way too big
for the sea snake to bite.

[dreamy music]

This snake is heading for the surface

to grab a breath of air.

A sea snake, just like a lands snake,

has lungs and must breathe air to survive.

It can hold its breath up to
three hours during a dive.

Recent research has shown
that some sea snakes can

also absorb a little bit of
oxygen directly from the water

through their skin,

which is probably why a
breath can last so long.

[dreamy music]

After spending a minute
at the surface breathing,

the sea snake comes
back down to the bottom.

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It's poking around,

looking for holes where it
might corner a fish or shrimp.

It sticks its head into the
holes hoping to get lucky.

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The sea snake is most closely
related to the cobra on land,

and its venom is quite
similar to cobra venom,

but considerably more potent.

If it manages to grab a fish,

the venom will k*ll it in seconds.

[dreamy music]

Sea snakes often take
a rest on the bottom,

sleeping as they hold their breath.

I use the opportunity to sneak up on one.

In spite of their fearsome venom,

sea snakes are very timid and
not particularly aggressive.

[dreamy music]

Although this one is
obviously not thrilled

about being picked up, it
doesn't try to bite me.

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And when I let it go, it just swims away.

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I find another one, and I
can't resist the opportunity

to show the flattened tail
section to the camera.

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Swim, be free.

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[water splashes]

Although the sea snake is one
of the most venomous animals

in the world, you're not very
likely to be bitten by one,

and the reason is because
they just can't open

their mouths very wide.

In fact, they have a
hard time even getting

the tip of my finger into their mouth.

In fact, the only place
you could really be bitten

by a sea snake is on a
thin little fold of skin

like between your fingers
or maybe on your lip.

There are 62 known species of sea snakes,

and they live all around
the tropical Indo-Pacific.

I found this banded sea
snake in the Philippines.

They like nice warm tropical water

because they're cold-blooded
like all reptiles.

If the water gets too
cold, they get lethargic.

So no matter what you
might think of snakes,

sea snakes are timid and shy animals

that represent almost no
threat at all to people,

even though they produce some
of the most powerful venom

in the world.

[dreamy music fades]

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

Jonathan spends a week
underwater at night waiting

for the coral to spawn.

But first, a look at the
incredible ways animals

in the ocean work together to survive.

- Many creatures in the ocean survive

by forming relationships or partnerships

with other creatures.

Perhaps the most famous
is that of the anemone

and the anemone fish,
sometimes called a clown fish.

An anemone is an invertebrate
that looks like a carpet

with stinging tentacles.

It's basically a
jellyfish that can't swim.

It stings and kills fish to
eat with these tentacles.

But this fish, the clownfish,

lives in the anemone's
tentacles without injury

because it's coated with a special slime

that tells the anemone not to sting.

The anemone provides
protection for the fish.

This is a perfect example of symbiosis.

The word symbiosis comes from a Greek word

that means living together,

but it refers to creatures
that have a relationship,

not just the ones that
are living together.

In the case of the
clownfish and the anemone,

they do live together.

This is how most people
think of symbiosis.

But take the example of
the cleaning station.

At a cleaning station,

one kind of fish gets cleaned by another,

such as this manta ray being
cleaned by a bunch of wrasses.

It hovers over the reef, and
the wrasses come right over

to pick the parasites from its gills.

This is symbiosis,

but the two animals definitely
don't live together.

And that's not the only thing confusing

about symbiotic relationships.

Although we tend to think
of symbiotic relationships

as being beneficial to both parties,

that's not always the case.

Take the case of the remora.

A remora is a fish with
a suction cup on its head

that allows it to stick to
larger animals like sharks,

dolphins, and turtles.

The remora survives by
mooching food scraps

and a free ride from its host.

They may provide some cleaning
services to their host,

but for the most part, they
seem to be freeloaders.

This is definitely a
symbiotic relationship,

but it's really only good for one party.

If the remora were to
harm the host in some way,

you would call it a parasite.

If the remora merely helps
itself without harming the host,

then this would be called
a commensal relationship

or commensalism.

The best kind of symbiosis
is called mutualism.

This is where both parties
get something out of the deal.

For example, take this hermit crab.

She has a garden of small
anemones on her shell

that she carries everywhere she goes.

The anemones give her protection
from predators like octopus

because their stinging
tentacles pack a punch.

[cheerful music]

But the anemones have a great
life living on her shell

because they gather some of the scraps

from her messy eating,

and they travel around
with her to the next meal.

[cheerful music]

Since the hermit crab uses an
old snail shell for a home,

she needs to find a larger shell

every once in a while as she grows.

When she finds one, it's
as simple as hopping

out of the old shell and into the new one.

But what to do about the anemones?

The anemones are so
important to the hermit crab

that she must also move
them to the new shell.

Without them, she's defenseless.

Slowly, with a combination
of tapping on the anemones

and peeling their edges,

the hermit crab convinces
them to release their grip.

Only the crab knows how
to coax the anemones

into letting go.

They will not submit to any
other creature pulling on them.

Once the anemone lets go of the old shell,

the hermit crab deposits
it on her new shell.

She simply plops it in place

and holds it until the anemone grabs on.

The anemone will then
crawl around on the shell

and find a good spot all on its own,

while the hermit crab turns her attention

to working on the next anemone.

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with the anemones
planted on her new shell,

the hermit crab has completed her move.

She leaves her old shell
for the next hermit crab

a bit smaller than herself.

[cheerful music]

Another crab has a
different symbiotic strategy

for survival.

This decorator crab grows
living sponges, hydroids, algae,

and tunicates on its body
to create camouflage.

When the crab holds still,

you will never see it against
the similar background.

Only when it moves does
it give itself away.

[cheerful music]

In the ocean, perhaps the
animals most commonly involved

in symbiotic relationships are shrimp.

Shrimp are found associated
with sea cucumbers, sea urchins,

sea stars, crinoids, nudibranchs,

anemones, coral.

You name it, they're everywhere.

Why?

Well, because they make great snacks.

Fish love to eat shrimp,

so shrimp need to be clever
to keep from becoming lunch.

[light music]

Out on the sandy sea
floor of the Philippines,

a fire urchin slowly makes
its way across the bottom,

feeding on algae.

The urchins venomous spines
protect it from most predators.

On top of the urchin, a
pair of Coleman shrimp ride

like first class passengers.

The shrimp have used their
claws to clear the spines

off a little spot they call home.

This is a commensal relationship,

because the shrimp get
protection from the urchin,

but they don't offer anything
in return to the urchin.

Neither do they harm the urchin,

so they're not parasites either.

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Another shrimp, another free ride.

This Spanish dancer is a large nudibranch,

a snail without a shell.

It's about the size of your hand.

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On its back rides an imperial shrimp.

The shrimp survives by
eating the nudibranch's poop.

It gets a free ride and a
meal from the nudibranch,

but it gives nothing in return.

[light music]

Here's a shrimp with a
little more to offer.

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This shrimp lives with a goby,

a small fish in a burrow in
the sand on the sea floor.

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The shrimp works hard to keep
the place clean and tidy,

constantly arranging the
rocks at the entrance

and shoveling out the
sand that gets inside.

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Why do all this work for the goby?

The shrimp needs someone to stand guard.

While it works,

the shrimp keeps one antenna
in contact with the goby,

while the fish keeps its eyes peeled.

[light music]

If the goby moves, the shrimp retreats.

This is classic mutualistic symbiosis

because both animals get

something out of their relationship.

[light music]

High above the shrimp's head
is a much larger animal,

a whale shark the size of a bus.

Swimming around it are
a few fish called jacks.

These fish are using the
whale shark as a bodyguard.

They know that nothing will
dare attack the whale shark,

it's too big.

So if they hang around, they're safe too.

The whale shark eats only
plankton and tiny fish,

so the jacks are safe from the
shark's humongous appetite.

[dreamy music]

These are only a handful of examples

of the symbiotic
relationships in the ocean.

There are thousands of different animals

all working together to survive,

and it's one of the things
that makes the blue world

so exciting to explore.

[dreamy music fades]

- [Announcer] Don't go away.

Jonathan is about to
head underwater at night

to learn how coral reefs spawn.

- Coral reefs are amazingly
beautiful underwater sculptures

that grow in tropical waters,

and provide essential habitat for fish

and invertebrates,

as well as form an important part

of the tropical ocean ecosystem.

Some coral, like this bushy gorgonian,

may look like a plant.

Other corals, such as this brain coral,

looks like a boulder on the sea floor.

But coral is alive and it's an animal.

Look close enough, and you'll
see hundreds of little mouths

such as the ones on
this star coral colony.

Each mouth belongs

to an individual coral
animal called a polyp.

Corals are related to jellies,

so think of a coral colony
as hundreds or thousands

of tiny jellies all clumped together.

Like jellies, coral has stinging
tentacles to catch prey,

which it mostly does at night.

But unlike jellies, corals
grow attached to the bottom

and often create a hard skeleton
to hold themselves down.

This begs the question,

how does an animal that
can't move reproduce

and make a new colony
in a different place?

I'm on a mission to document
how coral reproduces,

so I've come to Bonaire,

one of the greatest places in the world

to learn about coral spawning.

Biologists have been
studying coral reproduction

here on Bonaire for more than a decade.

Bonaire is an island in the southern part

of the Caribbean, near Venezuela.

It's a beautiful place
full of Dutch architecture

because it's part of the Netherlands.

The rocky windward shoreline
is rough, desolate,

and pounded by crashing waves.

[waves crashing]

But the other side of the
island is calm and tranquil,

where it's protected from the trade winds.

It's here that I'll be
diving to observe the coral.

[pensive music]

Coral reproduction is not the easiest

thing in the world to observe.

That's because coral
reproduces by spawning.

It only does it at night,

and it only happens a
couple nights per year.

I've come to Bonaire

a week after the full moon in September,

when the corals are predicted to spawn.

Why a week after the full moon?

Well, it has to do with the tides.

You see, during a full moon,

you have what's called a spring tide.

That's when the high tide is really high

and the low tide is really low,

and you have a huge
amount of water movement

between those two tides.

A week later, you have
what's called the neap tide.

That's when the high
tide's not quite so high,

and the low tide is not quite so low,

so you have a smaller amount of movement

between the two tides.

Less water movement means less current,

and less current means that the eggs

from the coral have more time
to float around in the water

and get fertilized before
the current takes them away.

As the sun sets, I prepare my gear.

Soon I'll be heading out for a night dive.

The coral spawn under
the cover of darkness.

Well, let's go see what's
happening on the reef.

I head down the steps of the
dock at Captain Don's Habitat.

Cameraman, Tim and I
are diving from the dock

because the reef is only a
few hundred feet offshore.

We can do as many dives as we need.

Down on the reef, I
start hunting for signs

that the coral might be ready to spawn.

It's pretty dark,

I can only see as far
as my flashlight beam.

I'm looking at each coral head closely.

If a coral colony is
getting ready to spawn,

the polyps will be swollen

with the eggs they're going to release.

[water gargles]
[dreamy music]

These don't look ready.

[dreamy music]

Movement catches my eye.

A spiny lobster is walking
down the reef slope,

so I take a few minutes to watch.

The spiny lobster has no big claws

like the lobsters in New England.

Instead, its long antennae are covered

in sharp spines for protection.

[playful music]

Nearby, an octopus is on the
prowl, hunting for dinner.

[light music]

I follow along with my
bright video lights,

but it doesn't take long
for the octopus to decide

that I'm not helping its
chances of finding a meal.

It gives me the slip with a squirt of ink

as it jets away into a hole.

After three hours underwater

with no sign of imminent coral spawning,

Tim and I decide to call it a night.

We're tired.

Well, that was a long night,
but no spawning tonight.

So, try again tomorrow.

The next day, I spend
a little time touring

around the island to see the sights.

First, a stop at Lake
Gotomeer to see the flamingos

for which Bonaire is famous.

Their pink color comes
from the shrimp they eat.

[relaxed music]

Next, I swing down to the
incredible Cargill salt works

to see the huge piles of salt created

by drying out sea water
in vast shallow pools.

[relaxed music]

And of course to downtown
Kralendijk for a few gifts

at a colorful gift shop.

[relaxed music]

But then it's time to
head back to the dive shop

to prepare for the night dives.

Tim and I examine

the predicted corresponding
times published

by the Bonaire National Park.

Okay, tonight on the 29th,

it is predicted to be the peak spawn.

Okay, so you'll notice we have
almost all of the species.

- If we can't nail it
tonight, we'll never nail it.

- No, tomorrow night, the star corals

and the brain corals
should still be spawning.

In fact, tomorrow night is
the peak for the brain corals.

After dark, I suit up again
for another long night.

Well, tonight's supposed
to be the peak spawn.

I'm hoping for a great
show, let's check it out.

[water splashes]

As I swim out to the reef,

I'm joined by a school of gigantic tarpon.

These big silvery fish
are as long as a bicycle,

and have learned to use divers lights

to find smaller fish to eat.

They follow Tim and I around all night.

On any other night,

I would film these magnificent
fish for the entire dive.

But tonight, I have work to do.

This is my fourth night
observing the coral

and my last chance to
capture the coral spawn.

I examine a coral head,

and I can see swollen
polyps filled with big blobs

that look like eggs.

They're actually called gamete bundles.

I get ready with my camera and wait,

the big moment is definitely coming soon.

[dreamy music]
[water gargles]

[dreamy music]

There, the colony has
released its bundles.

Since most corals are hermaphroditic,

the bundles contain both eggs and sperm.

They float up into the water and separate.

This allows eggs and sperm
from different coral colonies

to mix together and cross-fertilize
in the water column.

They all release at the same time

in order to overwhelm predators

that come in to feed on
this nutritious food source.

[dreamy music]

Soon the water is filled with coral spawn.

[dreamy music]

Not all corals are hermaphroditic though.

Some are gonochoric,

meaning they have separate
male and female colonies.

The male colonies are easy to spot.

When they release their sperm,

it looks like they're smoldering.

[dreamy music]

I train my camera on a big colony

of greater star coral and wait.

In spite of my camera's lights, it spawns,

releasing clouds of sperm into the water.

[dreamy music]

While I'm waiting for this coral to spawn,

a tarpon passes by checking
out what I'm up to.

[dreamy music]

Once all of these eggs are fertilized,

they will drift in the current for a while

and eventually settle down.

[dreamy music]

If they're not eaten,

and if they don't settle
into water that's too deep,

or land on sand where they
can't anchor themselves,

they might land on a nice
hard surface and take hold.

A new coral colony will start growing.

[dreamy music]

After several hours
observing the coral spawning,

it's time to head to shore
with our mission accomplished.

What an amazing spectacle.

Millions and millions of coral polyps

all releasing their eggs at the same time,

synchronized to the phase of the moon.

I mean, just an astonishing thing to see,

and it just goes to show
you that patience pays off.

Because our perseverance
over several nights

finally resulted in nature
giving us an incredible show.

As I exit the water and
head for a hot shower,

I'm thrilled to have witnessed one

of nature's secret spectacles.

It was worth all those
long nights of diving,

but now I'm ready for bed.

[waves crash]

[bright music]

[light music]