The ocean layers
The ocean is divided by depth into five main layers:
- the “hadalpelagic zone” between 11,000 meters (36,000 feet) and 6,000 meters (20,000 feet) deep,
- the “abyssal” between 6,000 meters (20,000 feet) and 4,000 meters (15,000 feet) deep,
- the “bathyal” between 4,000 meters (15,000 feet) and 1,000 meters (3,000 feet) deep
- the “midwater” between 1,000 meters (3,000 feet) and 200 meters (700 feet) deep
- the “epipelagic” (from 700 feet to the surface) where 90% of the living from the sea.
The “hadalpelagic zone” or “hadal zone” is the deepest layer in the ocean, extending from 6,000 meters (20,000 feet) deep to nearly 11,000 meters (36,000 feet) in the Mariana Trench in the Pacific with strong hydrostatic pressure of about 1100 atmospheres and temperatures between 1 ° C and 2 ° C above the melting point. This layer is in total darkness and extends in 75% of the ocean.
There are certain living organisms and creatures, which if removed from this area will die in areas of lower pressure, being the most common worms, jellyfish, sea cucumbers and certain fish. The currents observed behaviors related to the interaction of the Earth with the Sun and Moon.
The “abyssal” or “abyssopelagic” zone is between 6,000 meters (20,000 feet) and 4,000 meters (15,000 feet) deep, abiding in perpetual darkness and never receives the sun’s visible light.
The pressures are at about 400 atmospheres at 4,000 meters to 600 atmospheres at 6,000 feet deep with temperatures between 2 ° C and 3 ° C without inhabitants. The area is too dark for photosynthesis to occur so fish and shellfish in this area are blind or have their own light source.
The “bathypelagic”, “bathyal” or “midnight” zone is between 4,000 meters (15,000 feet) and 1,000 meters (3,000 feet) deep. Over 90% of the ocean lies beneath this layer.
On this layer the temperature is constant and is around 4 ° C, but the pressure increases from 100 atmospheres at 1000 meters to 400 atmospheres at 4,000 meters deep.
The darkness is constant. Sunlight does not reach this area, where only occur some flashes of light which come from the bioluminescence of animals in this area are scarce (sponges, brachiopods, sea stars) with slow rates of metabolism. There are no plants by the lack of sunlight to carry out photosynthesis.
The animals in this area do not have strong muscles. Sperm whales can dive at this level in search of food.
Among the 1,000 meters (3,000 feet) and 200 meters (700 feet) of depth is the “midwater” zone because sunlight is pale and penetrates up to 600 meters (2,000 feet) deep , thus this area is also known as “twilight zone” with few plants that can perform photosynthesis.
In this area occurs the “thermocline” where the water temperature drops suddenly as a transition layer between the “twilight zone” with the “zone of the Sun” (which in the tropics is greater) of 13 ° C to 200 meters deep with 20 atmospheres of pressure, and temperatures up to 4 ° C at 1000 meters (3,300 feet) of depth where the pressure is around 100 atmospheres.
In this area there can live certain fish, but due to the pressure, temperature and lack of sunlight, life is difficult in this area where there are animals which are highly efficient in the use of their energy and the absence of most of the predators. In this area there can be found most of the largest whales.
The ocean has a surface layer of warm water that goes from 12 ° C to 30 ° C from the first 10 meters or 20 meters to 50 meters, 100 or even to 200 m deep called the “epipelagic zone”, “sun area “or” photic zone “where most of the visible light exists in this area.
Additionally, it is a relatively hot zone which changes depending on the latitude and seasons, from 40 ° C in the Persian Gulf to -2 ° C at the North Pole. The pressure ranges from 1 atmosphere at the surface of the ocean to 20 atmospheres at 200 m depth.
The interaction of this layer with the wind keeps the mixture of this layer and allows the vertical distribution of the heat of the sun. It is a very stable layer. This area is where most of the underwater plants and primary production, with about 90% of marine life making a strong competition for food.