The Limits of Ocean Depth


      In today’s VERITAS we shall explore the deepest point of all oceans. We will see if life can survive the extreme conditions of these depths.

      The deepest point on earth is the Challenger deep located in the Marina Trench. This is located north of New Guinea in the Pacific Ocean. The depth of this point of the ocean is about 11 kilometres(6.8 miles). So if you could place Mount Everest there, it would be submerged with 1 km of water over its peak.

      We know very little about places so deep below the sea.

Light lasts to about 200 metres below the sea. By 500 metres it is pitch dark. The top 200 metres where there is still light is called the “photic zone”. Photosynthesis can only occur in this shallow zone. Below 100 metres the temperate drops to 2-3 degrees C.

Pressure increases rapidly. For every 10 metres the pressure increases by 1 atmosphere. SO extreme conditions start even before we reach the 500 metre depth. You can imagine( or can you?) the conditions at the bottom of Challenger deep. Would life survive there? Imagine the weight of 11 kilometres of water on you!

      Yes, there is life at the bottom of the Challenger deep.

There are certain organisms which absolutely need high pressure to maintain their body processes. These are called barophilic organisms. Their cell membranes have different protein composition. Their enzymes are bound differently. Normal enzyme bindings get weak with pressure.

      So the Challenger deep has life in the form of microbes which love pressure. It also contains more complex creatures. Shrimps, scale worms and sea cucumbers are also found there.

So we see that several different kinds of creatures live there.

What do they eat? They eat smaller organisms! But it has to start somewhere! Most the life that we are familiar with starts from the sun with plants producing food from sunlight. The rest of the creatures eat plants or other plant eating creatures.

At the depth of Challenger deep what is the primary source of energy?

Sunlight cannot reach there. What is at the bottom of the foodchain?

At the bottom of the foodchain are creatures that take energy from the hot core of the earth. The Mariana Trench has chimneys and hydrothermal vents which release smoke from the hot core of the earth. These hydrothermal vents release poison gas, heavy metals, acids, and heat. Some Creatures survive by oxidizing the hydrogen sulfide that is released by these vents. This process is called Chemosynthesis. 

The rest of the creatures eat these creatures. These hydrothermal vents are home to colonies of creatures that use the stuff released from them.

      These releases from the vents may seem like food for the organisms that live in the deep. Far from it. For most of these creatures these gases and heavy metals are extremely toxic. Also these vents create extreme heat that these creatures are not used to. Liquified heavy metals can clog the mouths of these creatures killing them instantly. Only for a small set of creatures these chemicals act as food. The rest just depend of these creatures and these stay away from the vents.

      Fish has been found till a depth of 8.5 kilometres( 5.2 miles) in the Challenger deep. These fishes have no eyes( no light so no eyes).

      How deep has man gone? The deepest that a man could descend was to a depth of just 90 metre from the Challenger deep floor.

Submersibles with robotic arms have touched the ocean floor several times.

      Some beautiful lines from Lord Byron’s poem: The Sea:


       Roll on, thou deep and dark blue Ocean,–roll!

       Ten thousand fleets sweep over thee in vain;

       Man marks the earth with ruin,–his control

       Stops with the shore;–upon the watery plain

       The wrecks are all thy deed, nor doth remain

       A shadow of man’s ravage, save his own,

       When, for a moment, like a drop of rain,

       He sinks into thy depths with bubbling groan,

      Without a grave, unknelled, uncoffined, and unknown.





  Go, wondrous creature! mount where Science guides:                 

  Go, measure earth, weigh air, and state the tides:                 

  Instruct the planets in what orbs to run,                          

  Correct old time and regulate the Sun;                              



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