Explanation

Major zones in fresh water body as lake are : (i) Littoral zone is the uppermost zone, which is shallow-water region. (ii) Limnetic zone is an open-water zone to depth, where effective light can penetrate, it is the chief ‘producing region’ in lakes. (iii) Profundal zone is zone of bottom and deep water area, where effective light cannot penetrate. It is found to be absent in ponds. (iv) Benthic zone is deep oceanic zone, which is cold, dark and devoid of producer organisms. Benthos are either detritus feeders or carnivores.