Day: June 25, 2022


Phytoplanktons are found on illuminated surface of water. On the other hand, benthic organisms are found at the sediments of a lake. Three zones in a lake can be identified which are determined by gradients of light, oxygen and temperature from the water surface to bottom.

Littoral zone: It is shallow water zone present at the edge of lake. It bears rooted plants.

Limnetic zone: It is present behind littoral zone and contains often water. Here phytoplankton’s are found in plenty. Light can penetrate from 20-40m.depthdepending on clarity of water.

Profundal zone (dark zone): In this zone light fails to reach. Bottom of lake constitutes benthic region where micro-organisms, snails and sluge etc. are found.