The main cause of eutrophication in water bodies is the excessive discharge of nutrients.


Excessive discharge of nutrients:
Eutrophication occurs when there is an excess of nutrients, particularly phosphorus and nitrogen, in the water. These nutrients come from sources such as agricultural runoff, sewage discharge, and fertilizer use. When these nutrients enter the water body, they promote the growth of algae and aquatic plants. As a result, the water becomes enriched with organic matter, leading to a series of negative environmental impacts.


Algal blooms:
The excessive nutrients in the water stimulate the rapid growth of algae, leading to algal blooms. These blooms can cover the surface of the water, blocking sunlight from reaching aquatic plants below. When the algae die and decompose, they consume oxygen in the water, leading to hypoxia or low oxygen levels. This can be harmful to fish and other aquatic organisms.


Loss of biodiversity:
Eutrophication can also lead to a loss of biodiversity in the water body. The proliferation of algae can outcompete native aquatic plants, reducing habitat availability for fish and other organisms. This can disrupt the entire ecosystem and lead to a decline in species diversity.


Water quality degradation:
As the algae decompose, they release toxins and foul-smelling compounds into the water, degrading water quality. This can make the water unsuitable for drinking, swimming, and other recreational activities. Eutrophication can also lead to the production of harmful algal blooms that can produce toxins harmful to humans and wildlife.


In conclusion, the excessive discharge of nutrients, particularly phosphorus and nitrogen, is the primary cause of eutrophication in water bodies. It is essential to manage nutrient inputs to prevent or mitigate the impacts of eutrophication on aquatic ecosystems.