Zonation in a Fresh Water Body

Zonation in a Fresh Water Body (Lake) :-

Large fresh water bodies constitute lakes .On the basis of productivity lakes are two types :-

1.       Eutrophic lakes :- 

The lakes rich in nutrient are called eutrophic lakes.

2.       Oligotrophic Lakes :- 

The lakes poor In nutrient are called oligotrophic lakes.

Deep lakes show photic as well as thermal zonation.

On the basis of light zonation , the swallow water banks constitute littoral zone . the open water limnetic zone , the deep water area or deep water  parts , where light cannot penetrate , is called profundal or aphotic zone , generally aphotic zone is absent in ponds & lakes.

On the basis of temperature strata , again three zones are there i.e., epilimnion , upper stratum which is exposed to sun rays. It is warmer during summer & comparatively cooler during winter. Hypolimnion is limnion is the zone of transition between epilimnion & hypolimnion

The maximum temperature , change occur in the middle portion of metalimnion , which is called thermocline

Transparency or turbidity of water is measured by an instrument called secchi disc