Ocean Zones

The dysphotic zone of the pelagic realm, from a depth of about 650-3,000 ft (200-1,000 m), is known as the mesopelagic zone. In the mesopelagic zone, a number of organisms survive by spending daylight hours within this zone and then rising toward the surface during evening hours. In this way, they can feed off the phytoplankton and zooplankton available near and on the surface of the water while avoiding predators during the day. The most common organisms found in the mesopelagic zone are small fish, squid, and simple shellfish.

A number of inhabitants of the deeper dysphotic zone have evolved some interesting adaptations for living in this twilight world. They often have very large eyes, capable of detecting light only 1% as intense as that visible to the human eye. A majority also have light-producing organs that give off a phosphorescence that makes them glow in the dark.