<Ul> <Li> Marine habitats </Li> <Li> Lake stratification </Li> <Li> Aquatic ecosystems </Li> <Li> Wild fisheries </Li> </Ul> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth . The word "pelagic" is derived from Greek πέλαγος (pélagos), meaning' open sea' . The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes from the surface of the sea almost to the bottom . Conditions differ deeper in the water column such that as pressure increases with depth, the temperature drops and less light penetrates . Depending on the depth, the water column, rather like the Earth's atmosphere, may be divided into different layers . </P>

What is the basis of energy in the open ocean