The light intensity decreases with increasing depth of the ocean water. This leads to the division of the ocean into three major zones, sunlight zone, twilight zone, and deep sea zone. The autotrophs like the phytoplankton live in the sunlight zone and perform photosynthesis using sunlight. Various fishes that eat planktons also live in the sunlight zone. The twilight zone is inhabited by various predators like the octopus, sharks and dolphins. Here the pressure of water also is greater. In the deep sea zone, no light is present. Fishes like the angler fish and other bio-luminescent organisms live here. This zone also contains chemotrophs as the producer of food. The pressure of water at this zone is the greatest which is not bearable by the organisms living above it. Thus in this manner light and depth determine the distribution of various organisms in the ocean.
