(i) Eutrophication is the natural aging of a lake (or any standing water source) by nutrient enrichment of its water.

(ii) The accumulation of nutrients such as nitrogen and phosphorus leads to excessive growth of aquatic plants, algae and animals thereby increasing the organic content of the lake.

(iii) Eutrophication is both natural and man-made. The natural one is a slow and gradual process which spans over thousands of years.

(iv) On the other hand, pollutants and wastes from man-made activities such as industries, excessive use of fertilizers, dumping of sewage into water bodies without treatment causes a sudden increase in the nutrient content in the water bodies. This causes excessive growth of algae over the surface of lakes in a very short period of time and hence is also called Cultural or Accelerated Eutrophication.