Water column

A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment. Descriptively, the deep sea water column is divided into five parts—pelagic zones (from Greek πέλαγος (pélagos), 'open sea')—from the surface to below the floor, as follows: epipelagic, from the surface to 200 meters below the surface; mesopelagic, from 200 to 1000 meters below the surface; bathypelagic, from 1000 to 4000 meters below the surface; abyssopelagic, from 4000 meters below the surface to the level sea floor; hadopelagic, depressions and crevices below the level sea floor.