3. what are the major sources of nitrogen and phosphorus in water? how could nitrogen and phosphorus-induced eutrophication affect the quality of water?

Major sources of nitrogen and phosphorus in water are river and agricultural runoff.

Explanation:

These can induce the eutrophication and effect the water's biological oxygen demand and can also damage the quality of water and hence create high levels of pollutants as these tend to block the sunlight and block the fish from breathing in it. The phosphorus that agricultural use deposited in water harms the ecological productivity of the water increase in the nutrient level of water and making it sedimentary. Due to the obstruction of the light coming from the sun the photic layer gets harmed and rise in algae blooms in water.