Story of Hidden Deep Sea Monsters

Story of hidden Deep Sea Monsters

Deep sea monsters or the Deep sea creatures are the animals that live below the photic zone of the ocean.

What is the photic zone of the ocean?

Photic zone also known as sunlight zone or limnetic zone is the uppermost layer of the ocean receiving sunlight and allowing photosynthesis to happen, forming the basis of food chain in the upper water column. The zone is 80m(260 feet) in depth and is home to majority of aquatic life.

What is deep sea? How deep is the deep sea?

Deep sea is the lower most layer of the ocean existing below thermocline and above the seabed. It is the darkest region of the ocean. The water is between 3-10 degree Celsius and has low or no oxygen. About three-fourths of the area covered by ocean is deep, cold, and permanently dark. Pressure of upto 1,000 atmosphere can be experienced in this zone.

The ocean is divided into three vertical zones of the water column based on the amount of light and pressure it experiences and these are: Sunlight zone, Twilight zone, Midnight zone.

Twilight zone – only faint light reaches this zone. Due to lack of sunlight, bioluminescence can be observed in creatures. No plants grow in this layer, one can find some strangest sea animals such as octopus, crab, krill, swordfish, wolf eel, and catshark.

Midnight zone or the deep sea consists of two zones abyssal or hadal zone.

Abyssal zone is 4,000-6,000 metres in depth with perpetual darkness with very little oxygen. Has higher concentration of nutrient salts, like nitrogen, phosphorus, and silica, due to the large amount of dead organic material that drifts down from the above ocean zones and decomposes.

Abyssal zone is above Hadal zone. Hadal zone is lying within oceanic trenches. Found at the depth of around 6,000-11,000 metres, making it a deepest region of the ocean.  Most hadal habitat is found in the Pacific Ocean.

How do the deep sea creatures survive without light?

As there is no sunlight, the microbes depend on chemicals that come out of the vents. The process is termed as chemosynthesis and the microbes capable of this process are called chemoautotrophs. The chemoautotrophs oxidizes hydrogen sulphide, hydrogen and methane, readily available from the hydrothermal fluids and creates an energy surplus In the form of sugar which the bacteria then utilizes to produce organic matter. The bacterial mats formed in this process serve as  sole food source for the crustaceans, that then in turn are eaten by larger organisms, which then are also eaten by even larger organisms.

What is bioluminescence which the creatures in deep sea exhibit? What is its relevance?

Bioluminescence is the ability of living organisms to produce light. The light is produced by bacteria within light-emitting cells called photophores. It is the same phenomenon which is observed in fireflies and mushrooms. In the deep sea ocean it is commonly observed in squids, siphonophores, jellyfish, and comb jellies.

Bioluminescence helps organisms to deter or hide from predators, helps them to find food by luring the prey and to find a mate for reproduction.

                     Deep Sea Creatures exhibiting bioluminescence

What is deep sea gigantism observed in deep sea creatures?

Deep sea gigantism refers to the large body size of the creatures. There are multiple factors causing gigantism in deep sea creatures.

  • The drastic fall in temperatures leads to increased cell size which results in continual growth of the organisms through out their life.
  • Lack of oxygen at greater depths leads to a slower metabolism rate, helping them to conserve energy which is another factor behind their increased body sizes.
Colossal squid – weighs 750kg
Lion’s Mane Jellyfish – 120 feet
                                                   Giant spider

How have deep sea creatures adopted to such high pressures?

The pressure at Challenger Deep in the Mariana Trench, the deepest part of all the world’s oceans is around 1,000 bars or more. Deep sea creatures here have adapted to such pressure and this is because deep sea creatures are largely made of water having minimal or no air gaps in the body. Water, being in-compressible, leaves their bodies unaffected by such great underwater pressure.  

Example: Hadal snailfish, the deepest dwelling species of fish which can be found at about 8,200m depth.

How are creatures in the deep sea living at such lower temperature?

According to researchers, an antifreeze protein is observed in fish’s blood which affects the water molecules in its vicinity such that they cannot freeze, and everything remains fluid.

Are deep sea creatures immune to threats?

Despite living at such greater depths, deep sea creatures are not immune to anthropogenic threats.

  • Deep sea mining is scooping away the sea beds damaging the deep sea ecosystem.
  • Global warming is making the ocean temperatures warm and it’s affect has been felt at the deep sea as well. Deep sea creatures have adapted to cold waters since centuries, sudden rise in temperature will disrupt their biological cycle leading to their death.
  • Fertilizers, pesticides, oil spills are other issues which badly damages the deep sea ecosystem killing the marine life instantly.
  • Microplastic is another menace to deep sea creatures.

Given the vast size, only 4% of the ocean is explored.

Introducing some of the deep sea creatures:

Frilled shark

Prefer to remain in the depths up to 5,000 feet (1,500 meters). They are considered living fossils, who swam the seas in the time of the dinosaurs. It’s a 5.3-foot species.


The fangtooth is the deepest-living fish ever living at a depth of 6,500 feet-16,500 feet. It’s about 6 inches long.

Six-Gill Shark

Six-gill sharks is found at 8,200 feet (2,500 meters) depth and surface at nights to feed. These  are of 16 feet(4.8 meters) long.

Pacific Viper fish

Pacific Viper fish has jagged, needlelike teeth so outsized it can’t close its mouth. These are only about 8 inches (25 centimeters) long. They troll the depths up to 13,000 feet (4,400 meters) below.


Published by LakesOfIndia

Lakes of India is an E.F.I initiative aimed at sensitizing the larger public on freshwater habitats across the country. A blog platform where one can read about lakes across India. You can become a guest blogger to write about a lake in your hometown and initiate an action to protect that lake.

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