Marine Biology

Zonation of sea on the basis of intensity of light

On the basis of the penetration of light, the ocean is vertically divisible into three zones:-

a. Euphotic stratum – This extends from 0-80 meters. This may also be called as “illuminated zone” of “Producing zone”. This zone is very rich in phytoplankton and primary consumers and secondary consumers.

b. Dysphotic stratum – This zone extends from 80 to 200 meters and is weakly lighted. Animals here are mostly secondary consumers and a few primary consumers. Plant life is rare.

c. Aphotic stratum – This zone extends below 200 meters where light is completely absent. The producers are absent as photosynthesis cannot take place. The animals in this region are secondary consumers and also feed on other animals. The only light available in this zone is mainly of light produced by the bioluminescent animals (living light or cold light).