During an educational trip, a student of botany saw a beautiful lake in a village. She collected many plants from that area. She notices that villagers were washings clothes around the lake and at some places waste material from houses was destroying its beauty.
After few years, shw visited the same lake again. She was suprised to find that the lake was covered with algae, stinking smell was coming out and its water had become unusable. Can you explain the reason for this condition of the lake ?

Explanation

The inflow of the waste material from houses and fertilizers of the plants and the entry of detergents into Water results in the increase of phosphate into water. As a result, formation of algae is accelerated which covers the water surface and concentration of dissolved oxygen decreases, i.e. process called eutrophication occurs