Light Stratification - Lake Ecosystem

The penetration of light in water bodies is limited depending on the transparency of water and its ability to absorb light. On the basis of light penetration lakes become vertically stratified into two basic layers

(1) The upper trophogenic zone corresponding roughly to the photic zone in which photosynthesis dominates and the lower, and

(2) Tropholytic zone where' decomposition is most active and which corresponds to the aphetic zone.

Between these two zones is the compensation depth - the depth at which light intensity is such that the photosynthetic production is just enough to balance respiratory losses and beyond which light penetration is so low that it is no longer effective. Generally compensation depth occurs where light intensity is about 100 foot candles or approximately one per cent of full noon sunlight incident to the surface.