Deep-sea organisms are animals that live beneath the euphotic zone of the ocean. The euphotic zone is the upper layer of the ocean that receives sufficient sunlight to support aquatic plant life.
Ways Deep-Sea Creatures Survive in the Ocean Depths
Most deep-sea organisms live thousands of meters below the water’s surface, far from the euphotic zone. The survival challenges these animals face include food scarcity, high water pressure, low oxygen levels, darkness, and extremely cold temperatures.
Pseudoliparis fish found in the Mariana Trench at a recorded depth of 8076 meters.
Deep-sea organisms include species such as whales, seals, crabs, sea urchins, fangtooth fish, giant tube worms, vampire squids, Pacific sharks, anglerfish, red-lipped batfish, dumbo octopuses, hairy frogs, coffin fish, blotched handfish, zombie worms, and many others.
How have all these species adapted to survive in the deep-sea environment?
Retaining Less Oxygen
Some fish can survive at depths of over 8000 meters beneath the sea surface. At this depth, the water pressure is equivalent to the weight of tens of millions of kilograms. However, the oxygen in their lungs is what helps counteract the crushing pressure of the water.
Therefore, before diving, many deep-sea creatures exhale nearly 90% of the air in their lungs and retain only about 10% of the available oxygen for use. This mechanism of utilizing less oxygen helps these organisms adapt to the extreme pressures found at the ocean floor.
Deep-sea creatures typically move slowly to maximize oxygen efficiency.
Ability to Hold Breath for Hours
With the limited oxygen left in their lungs, deep-sea creatures have developed other extraordinary abilities to adapt. Among these is the capacity to hold their breath for hours.
Some whale and seal species have amazed the world with their breath-holding capabilities in high-pressure deep-sea waters. For example, the Cuvier’s beaked whale can dive to depths of 2992 meters and hold its breath for a record time of 2 hours and 18 minutes. On the other hand, elephant seals can hold their breath underwater for up to 2 hours.
Super-compressed Lungs
The Cuvier’s beaked whale is the deepest diving species. Under water pressure, their lungs collapse to a thin layer, forcing all the gas in the lungs into their muscles and blood, where it gradually dissolves.
The muscles of the Cuvier’s beaked whale have adapted to store more myoglobin, and their blood contains more hemoglobin, allowing them to retain oxygen for extended periods in their bodies.
Cuvier’s beaked whale, a species with a unique structure that allows them to thrive in various aquatic environments.
Ability to Self-reduce Heart Rate, Lower Activity Function
In some organisms, the heart rate can drop to around 4 beats per minute, while others may nearly stop breathing for extended periods while diving.
Additionally, some deep-sea creatures drift in the water instead of using force to move. Drifting is a process that does not require muscle movement, helping conserve oxygen for surfacing.
Moreover, under high pressure, some organisms, like whales and seals, also reduce metabolic activities, such as halting digestive, liver, and kidney functions.
Presence of Trimethylamine N-oxide (TMAO)
Trimethylamine N-oxide (TMAO) is an organic compound found in the amine oxide class. TMAO is found in the tissues of crustaceans and marine fish.
This substance prevents water pressure from deforming proteins, which can be lethal to animals when they descend below certain water depths. Interestingly, the concentration of TMAO in marine organisms increases with the depth at which they live. With this compound, some deep-sea creatures can survive without suffering from protein deformation.
The body of an organism undergoing deformation.
Not Absorbing Nitrogen
Humans have a limited deep diving capacity because, in high-pressure environments, breathing is accompanied by high-pressure air.
The oxygen in this environment gets depleted through the body’s circulatory process, leaving nitrogen, which is easily dissolved in blood, tissues, and fats. Notably, the amount of dissolved nitrogen increases with rising pressure and time spent underwater.
If a diver surfaces too quickly, the sudden drop in water pressure causes nitrogen in the blood to expand, creating gas bubbles that can obstruct blood vessels. This phenomenon is similar to opening a carbonated beverage bottle. The gas bubbles can block blood vessels or compress vital organs, causing long-term harm and leading to decompression sickness.
Therefore, for deep-sea organisms, not absorbing nitrogen is a superior protective mechanism that not all species can achieve.
