Dear student,The process of aging of a water body due to excessive growth of algae and other aquatic organisms in the water bodies as a consequence of nutrient enrichment (especially nitrogen and phosphorous) is called eutrophication.It leads to water pollution.2 ways are: A polluted water body contain toxic materials including the heavy metals like nitrogen potassium etc. These promote the algal growth in the water body. Algae reduces the oxygen supply of the aquatic animals and results in the aging of water body as it takes away all the nutrients of the water body.(2).The dead microbes causes smell in water bodies.Regards.