We, humans have ventured into space
to a distance of around 4 lakh km.
This was achieved 
during the Apollo 13 mission in 1970.
We have studied a lot more about the celestial objects
than what lies in the depths of our ocean.
Oceans are no less than space.
They are a whole world themselves
and hold much wonders.
The Titanic ship sank in 1912 in the Atlantic Ocean.
Many proposals to uplift the wreckage of the ship
from the ocean floor were put forward
by the family members and 
relatives of wealthy passengers
who were aboard the ship.
But lack of deep sea diving technologies at that time
and outbreak of the first world war
put off the proposals.
It was only in 1985 a joint French-American expedition
discovered the wreckage of the Titanic,
600 km south east of Newfoundland coast,
at the depth of around 3800 meters.
So what are the harsh conditions in the deep sea
that dragged the discovery of the ship
so long since it's sinking?
How do organisms live in the deep sea
and what kind of adoptions do they have?
Let's move into the video.
High pressure, very cold conditions and absence of light
makes the deep ocean ecosystem difficult one to study.
So very little about the deep sea was known to us
until the Challenger expedition between 1872 and 1876.
The scientific expedition program
led by the Royal Society of London
laid the foundation of oceanography.
New discoveries created interest in
under-water topology, life of marine organisms
and various properties of ocean water.
Oceanography divides the ocean into 4 different layers
based on the temperature, density
and the amount of light at different depths.
They are called epipelagic,
mesopelagic,
bathypelagic
and abyssopelagic.
Epipelagic zone is found upto the depth of
200 metres from the surface water.
This zone is also called the photic zone
beyond which penetration of light gets reduced.
Free floating plants called phytoplanktons
produce their food using sunlight
which inturn is consumed by zooplanktons and fish.
Next comes the mesopelagic zone
which is found between 200 metres to 1000 metres.
Light availability in the ocean water
starts decreasing from this zone.
Hence It is also called the twilight zone.
In the mesopelagic zone,
most of the animals have transparent bodies.
Bioluminescence is seen as a major adoption
which is used as camouflage to protect from
predators as well as to confuse or frighten them.
As there are no primary producers in this zone,
animals move to the epipelagic zone
during night times for food.
The Bathypelagic zone is found 
between 1000 metres to 4000 metres
and this is where the Titanic ship lies.
With almost no sunlight after this zone,
the only source of light is bioluminescence
of bacteria and animals.
Food consists of falling organic matter
known as 'marine snow' and carcasses
derived from the productive zone above,
and is scarce both in terms of
spatial and temporal distribution.
Species in this zone have no skeleton
and have a fleshy body that enables them to
withstand high pressure and float using buoyancy.
Abyssopelagic zone is found beyond
4000 metres upto the deep ocean plains.
In deep layers,
the animals have dark colours like red, brown and black.
Because of the complete absence of primary producers
and other species at the bottom of the food-chain,
the number of big animals is less in the deep sea.
Animals in this zone majorly feed on detritus
and biological waste falling from the upper zones.
Detritus reaching the muddy abyssal plain
is eaten by sea urchins, sponges,
sea anemones, tube worms and bacteria.
Animals follow different strategies to feed.
They sit and wait until their prey falls in their way
or carried to them by deep ocean currents.
Scientists further add one more layer
to the classification.
Ocean floor also has deep trenches
as we have canyons on earth's surface.
This zone is called a hadic zone.
Pressure is the major obstacle
for reaching great depths in oceans.
For every 10 metre increase in depth,
pressure increases by 1 atm.
At the deepest point of the ocean,
pressure will be 1000 times
more than that of earth's surface.
However the deepest point on earth
was reached in 1960.
The Bathyscaphe Trieste descended
to the bottom of the Mariana Trench near Guam,
at 10,911 metres, the deepest known spot in any ocean.
It is important to point out here that
the highest peak on earth, Mount Everest,
is just  8,848 metres.
Such a massive ecosystem is being exploited
by a non-marine species,
which is none other than homo sapiens,
the so-called humans.
We exploit fishes beyond their reproduction rate,
dump sewage and radioactive wastes.
Activities like deep sea trawling, oil exploration
and mining are also destroying the marine ecosystem.
It is high time we understand its 
importance and start preserving them.
