Explain how, the use of pesticides in agriculture causes water pollution.

The use of pesticides in agriculture is responsible in causing the water pollution. It is also caused due to the excessive use fertilizers in the fields. These fertilizers act as nutrients for the algae to grow. When these algae die, they act as a nutrient for decomposers like bacteria. As a result of this process, a lot of oxygen in the water gets used up and leads to the deficiency of Oxygen in the water. This may kill the aquatic organisms.