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Adaptation under water

Visitors have accessed this post 149 times.



The immense pressure found deep beneath the ocean’s surface. Just 4 kilometers down, is capable of crushing even the sturdiest vehicles. Surprisingly, numerous creatures inhabit depths of 11 kilometers. The Mariana Trench is the Earth’s deepest oceanic trench, plunging to a depth of 36,000 feet (11 km). Notably, the Atlantic Ocean became the final resting place for the ill-fated Titanic, which sank at a depth of 3.8 kilometers. At such depths, the pressure is a staggering 400 times greater than that of the atmosphere.

The Survival Adaptations of Fishes:

In our bodies, the nasal cavity, lungs, and digestive system are filled with air, enabling them to withstand atmospheric pressure. However, these organs are unable to endure the pressure at a depth of 11 kilometers and would collapse under it. Unlike humans, fish do not rely on breathing air. Instead, they extract dissolved oxygen from water and utilize it for respiration. Whereas our bodies contain a substantial amount of air, fish bodies are filled with water, which effectively offsets the pressure at any oceanic depth they venture into.


The Swim Bladder:

Not all fish lack air within their bodies. Many fish possess a swim bladder, an internal organ that aids in buoyancy control and serves other functions. Thanks to this swim bladder, numerous fish species can venture to greater depths where pressure is significantly higher. Unlike our lungs, which cannot withstand the depths of the ocean, fish with swim bladders can cope with pressure at any oceanic depth. However, it’s important to note that not all deep-sea fish possess swim bladders. Whales, which reside near the ocean’s surface but can travel up to eight kilometers deep, fall into this category.


The Adaptations of Whales:

Whales, like humans, are air-breathing creatures that once inhabited land before transitioning to a fully aquatic lifestyle. While humans would perish at great depths in the ocean due to lung collapse, whales have developed a remarkable adaptation. Before descending to deep depths, they rise to the ocean’s surface and expel 90% of the air from their lungs, retaining only 10% of oxygen. This 10% is then mixed with their bloodstream, maintaining it in a liquid state. Consequently, their bodies compensate for the high-pressure depths by eliminating air from their lungs. Whales possess myoglobin, a protein that stores oxygen carried by hemoglobin and is used for future needs. This myoglobin-rich trait is also present in fish that frequently transition between the ocean’s surface and deeper depths, such as the elephant seal fish. Myoglobin facilitates oxygen transportation to the muscles, enabling them to descend to great depths with minimal oxygen intake. When we breathe, some nitrogen enters our bodies along with oxygen. However, when exposed to high pressure, nitrogen accumulation increases. Divers who surpass a certain depth experience increased nitrogen levels, resulting in the formation of bubbles in their blood vessels, leading to unconsciousness or even death. By contracting their lungs and retaining only 10% oxygen in liquid form, whales avoid this danger and remain unharmed even at high pressure. Thus, they rely on only 10% oxygen to navigate the ocean’s depths. Consequently, their metabolic processes slow down, including those of the digestive system, liver, kidney, and heart rate, which decreases to four beats per minute. When resurfacing, whales refrain from using their muscles, as they have already stored sufficient oxygen within them. Utilizing their muscle reserves helps conserve oxygen, which gradually depletes when used.


Adaptations and survival strategies employed by organisms that live at great depths in the ocean:

Here’s a summary of the key points:


Structural Adaptations:

             The bones of deep-sea creatures are not completely made of calcium but are cartilaginous, making them more flexible and capable of withstanding high pressure.

The cell membranes of these organisms are composed of unsaturated fats, which prevent the liquid inside their cells from freezing in extreme cold temperatures.


Pressure Adaptations:

The deep sea experiences immense pressure, but organisms have developed adaptations to cope with it.

Trimethylamine N-oxide (TMAO) is a substance found in the bodies of deep-sea fish. It is soluble in water and helps keep their bodies hydrated, enabling them to withstand the external pressure.

TMAO also increases the salinity of their bodies, aiding in compensating for the pressure of the surrounding water.


Energy and Nutrition:

Photosynthesis is not possible at great depths due to the absence of light. Therefore, there are no plants or algae to serve as a food source.

Deep-sea organisms rely on the nutrients brought by underwater volcanic eruptions. These eruptions transport nutrients from the Earth’s depths into the ocean, providing food for smaller species.

Larger fish obtain their necessary nutrients by feeding on these smaller organisms.



They are luminous in extreme darkness of depth of the sea.



These adaptations allow organisms to survive in one of the most challenging environments on Earth, where extreme pressure, darkness, and low temperatures prevail. By utilizing unique biological mechanisms, they have found a way to thrive and sustain life in the deep sea.




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