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Benthic means living or occurring at the bottom of the water body. The benthic zone includes the water layer present just above the bottom. Hence, the water in the benthic zone always contacts the bottom of the lake or ocean. The location of the benthic zone depends on the depth of the water body. In the deep ocean, sunlight may not reach the benthic zone, leaving it darker. Therefore, the temperature of the benthic zone is also low. Also, due to the weight of the large volume of water above, the benthic zone has to withstand a great pressure.

Pelagic means occurring or living in the open area of the water body. The pelagic zones include the topmost layers of the water body, which perform important ecological functions such as heat absorption, oxygen absorption, and food production through photosynthesis. As the availability of sunlight, oxygen, and temperature decrease and the pressure increases with the increasing depth of the water body, the pelagic zone can be subdivided based on the fluctuation of the factors.