Red Sea

The Red Sea.

A special idyll of the Orient.

A place of silence, strength

and diversity.

The Red Sea is famous for its high salt content

which especially contributes to clear water.

Algae can't spread easily here.

This is why its broad coral reefs

can be considered a true paradise for divers.

We can find lots of highlights of marine life here.

There are a lot of colourful shoals of fish,

popular anemone fish,

basses,

vigilant morays,

odd pufferfish,

and, of course, elegant turtles.

The biggest attraction is colourful coral reefs

shining in the sunlight.

From the Earth's orbit,

we can clearly spot the elongated form of the Red Sea.

It is a narrow sea,

2,240 kilometres long,

up to 2,604 meters deep,

that borders the Indian Ocean

and lies between Northeast Africa and the Arabian Peninsula.

The Red Sea contains about 200,000 cubic kilometres of water.

Its surface is spread over 438,000 square kilometres

and the water is on average 538 meters deep.

A good question would be why it is called the Red Sea.

There have already been several interpretations for it since antiquity.

On the one hand, blue algae grows in this stretch of water.

It swims right under the surface of the water.

In its flowering season, it becomes red.

This is why the water seems to be red

if you look at it from above.

But this plant isn't widespread.

Another explanation for the name

could be the red rocks at the Red Sea's coast.

They are red because they contain ferric oxide

which causes that shade.

According to legend,

those rocks have been burned red by the sun.

The Red Sea could also have got its name from Iranian seafarers

who used colours to name the four points of the compass.

The colour of the South was red.

The sea is geologically very young.

It was created 25 million years ago

because of the separation of the African and Asian continental plates.

Then the crack was filled with sea water

and the Red Sea was born.

Because of the constant drift of those continental plates,

the Red Sea widens out 1.2 centimetres on average per year.

The south of the Red Sea is especially interesting for us.

Over there, where Eritrea, Djibouti and Yemen border the sea,

right in the direction of the Indian Ocean.

There is a narrow place in this area

where the sea is only 29 kilometres wide

and only 130 meters deep.

Because of this natural bottleneck,

there is only a sluggish water exchange

which causes a high salt content.

In these conditions, plankton and algae can't spread easily

and the water seems to be crystal-clear

as we can already observe from the shore here.

But also under the water,

the view is much better than elsewhere,

as we are about to see now.

The most widespread creature

is, as well, the most important one:

the coral.

The fire corals and madrepores, the stone corals,

are the main constructors of the Red Sea's giant reef.

For thousands of years,

these animals have been forming enormous constructs,

right up to whole islands, all over the world.

The best known among them are the Bahamas, Bermuda,

and the Maldives.

That is possible because corals,

which belong to the group of cnidarians,

perpetually excrete limestone.

The zooxanthellae, a microorganism that lives inside the coral,

helps the corals to form lime.

They live in symbiosis,

which means that they provide and care for each other.

These corals are really sensitive to water temperature.

It always has to be between 20 and 29 degrees Centigrade.

Therefore, they mostly live in shallow, tropical and lighted waters.

Stone and fire corals

are actually just giant colonies of polyps.

Every polyp is only a few millimetres up to one centimetre long.

Besides the sustenance through their symbiotic partners,

corals mainly feed on planktonic organisms

which they catch with their tentacles.

Fire corals got their name from their cnidocytes, or stinging cells,

with which they can pierce through human skin

and inject a painful poison.

The symptoms are comparable to skin contact with a stinging nettle.

But the pain can persist from two days to up to two weeks.

The injuries can even leave scars that can be visible for a lifetime.

That's why divers should be really attentive

and careful not to make the common mistake

of confusing fire corals with seaweed.

As for distribution between sessile animals,

fire corals are really successful.

When fighting for light and living space,

fire corals can effectively overrun their rivals.

These corals also have so-called defense polyps,

somewhat bigger polyps than the usual ones,

which they use in their fight for a spot on the reefs.

They use them to sting their opponents' tissue

and thus, destroy it by poisoning it.

But the fish that you can see here

are not impressed by that.

The Anthiinae, a special kind of bass.

Actually, with them it's quite the contrary.

Living in groups of thousands,

they use the corals' complex formations

to hide from their predators.

What's interesting is that almost all of these fish are females.

Usually, only one fiftieth of the group are male.

At first, adult fish are always females

that later turn into males.

But that mostly just happens if a male fish dies.

If that is the case, the strongest female of the group

transforms into a male fish in just a couple of days,

to take its place.

Another resident of the reef is the soft coral.

Even though it is related to the stone and fire coral,

it has a totally different structure.

It gets its stability from inner water pressure.

Its limbs and strains are not covered in polyps.

Those are located at the ends of the arms.

The soft corals' colours are usually brown, yellow or green.

If it lives in the shadows,

it has a bright red, orange or purple colour.

Mostly, they are located on the edges of reefs,

overhangs or on the ceilings of caves.

Corals are really important for a lot of fish.

They provide shelter for small and normal sized ones.

That's why they are almost always surrounded by huge swarms.

If there's an enemy,

they can instantly hide between the branchy corals

and are almost unreachable for big predators.

The coral's ability to emit stinging poison

is a huge advantage here, too.

Although, the fish have to be careful

not to come into contact with the defense polyps,

because otherwise they themselves might be the victims.

Because of natural barriers

and because of the environment

influencing those animals in a special way,

many unique species which can't be found anywhere but the Red Sea

have developed over millions of years.

One of those creatures is the popular clownfish.

This genus here is also known as the Red Sea anemonefish.

They eat plankton and algae

and are comparatively small.

Fifteen centimetres is the maximum.

The clownfish lives closely in a so-called symbiosis with anemones.

That means, as we have just learned about the corals,

that two different species both profit from living together.

Surprisingly, clownfish are able to live with anemones

although its cnidoblasts are toxic.

Why doesn't it disturb the clownfish?

Very simple.

It possesses a slime layer

which protects it from the deadly poison.

The anemonefish protects the anemone,

driving out predators like, for example, butterflyfish.

In return, the anemone protects the anemonefish from predators.

And those can even be rather funny looking creatures like cornetfish.

Some of them can become much bigger than a meter.

Those sit-and-wait predators drift inconspicuously in the water

to suddenly snatch smaller fish.

This is why they are often pretty shy

and take to their heels as soon as they spot a diver.

Let's continue our way under the surface of the water

in search of the most colourful fish of the coral reef.

And here we see a royal angelfish.

They grow a little bit longer than anemonefish,

up to 60 centimetres.

The bluecheek butterflyfish

is one of the most eye-catching reef fish.

They can differentiate their fellow species

and other butterflyfish through their colouring.

Most of the time they live in couples

and sometimes in smaller groups, too.

A rather inconspicuous inhabitant of the Red Sea

is the orbicular batfish.

It's pretty flat and high.

But the older it gets, the more it becomes discus shaped.

Characteristic for its shade

are the vertical and brown bands.

Thanks to this high contrast,

some predators can't recognize the form of the fish easily

and assume them to be leaves washing through the sea.

Older fish seem to be more silver and grey

so that they look even more inconspicuous.

In spite of their inconspicuous appearance,

orbicular batfish are very active and curious.