Layers of the ocean

Ocean is much more deeper than the elevation of the land area on the continent. As you can imagine that the highest point in the continent is around 8800m from the mean sea level while the deepest part of the ocean is 11000m deep from the mean sea level.

This deep and thick water column can be divided into many layers as follows :

• Epipelagic Zone : This surface layer is also called as ‘sunlight zone’ and extends from the surface to 200m. It is in this zone that most of the visible light exists. With the light comes heating from Sun which is responsible for wide change in temperature that occurs in this zone, both latitudinal and seasonal.
• Interaction with the wind keeps this layer mixed and thus allows the heating from the sun to be distributed vertically. At the base of this mixing layer is the beginning of the thermocline.
• The depth and strength of the thermocline varies from season to season and year to year. It is strongest in the tropics and decrease to non-existent in the polar winter season.

• Mesopelagic Zone : Below the epipelagic zone is the mesopelagic zone, extending from 200m to 1000m. The mesopelagic zone is sometimes referred to as the ‘twilight zone’ or the midwater zone. This is the zone which contains the thermocline.
• Because of the lack of light , it is within this zone that bioluminescence begins to appear on life. The eyes on the fishes are larger and generally upward directed, most likely to see other animals against the dim light.

• Bathypelagic Zone : The depths from 1000m to 4000m comprise the bathypelagic zone. Due to it’s constant darkness, this zone is also called as ‘midnight zone’. The only light at this depth comes from the bioluminescence of the animal themselves. The temperature in this zone is constant, and never fluctuates far from a chilling 4⁰C.

• Abyssopelagic Zone : It extends from 4000m to 6000m. It is the pitch-black bottom layer of the ocean. The water temperature is nearly freezing and only a few creatures can be found at these cursing depths.

• Hadalpelagic Zone : The deepest zone of the ocean. It extends from 6000m to 10994m in Mariana trench off the coast of Japan. The temperature is just above freezing. The weight of all the water over head in the Mariana trench is over 8 tons per square inch.
• Even at very bottom life exists. In 2005, tiny single-celled organisms, called foraminifera, a type of plankton, were discovered in the challenger deep trench southwest of Guam in the Pacific-ocean. The deepest a fish have ever been found, abyssobrotula galatheae was in the puerto rico trench at 8,372m