A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons…
A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this?
Lots of urea and phosphate fertilizer were used in the vicinity.
The area was sprayed with DDT by an aircraft.
The lake water turned green and stinky.
Phytoplankton polulations in the lake declined initially thereby greatly reducing photosynthesis.
Solution
Part of fertilizers added to crop fields are passed down to water bodies during rains through surface run-off. Presence of extra nutrients brings about dense growth of plant and animal life. The phenomenon is called eutrophication. Eutrophication leads to organic loading, depletion of oxygen, death of animals and fouling of water.