State the effects of freshwater pollution. How is it caused?

The effects of freshwater pollution are:

1. Eutrophication and death of aquatic animals — Nitrate and phosphate accumulate in water bodies with run off water. They may be derived from fertilizers and detergents. They overstimulate the growth of aquatic plants and algae, resulting in eutrophication.
2. Disturbance in aquatic ecosystem — Leached heavy metal and chemicals may kill aquatic animals and plants disturbing the aquatic ecosystem.
3. Oil spill results in a layer of oil over the water surface, insulating the water from the atmosphere. This lowers the level of dissolved oxygen in water and ultimately leads to loss of aquatic life.
4. Many industries dump hot water in the freshwater bodies which raises the temperature of water and causes adverse effects on the aquatic creatures.

Freshwater pollution is caused due to:

1. Natural sources — The natural sources are gases, animal waste, living organisms, soil, minerals (Nickel, Cobalt, Lead and Mercury etc.) and other pollutants soluble in water.
2. Human sources — Urbanization and industrialization have resulted in excessive water pollution. The human sources of water pollution can be classified as follows:
   1. Sewage and Domestic waste
   2. Industrial waste
   3. Agricultural waste
   4. Nuclear waste
   5. Oil spills
   6. Thermal pollution