Excessive fertilizer use on farm land can increase nitrogen and phosphorus levels in water from runoff and decrease dissolved oxygen levels.

a. true
b. false

True

Explanation:

Eutrophication is a natural phenomena, in this the fertilizers which are rich in concentration of nitrogen and phosphorus due to the effect of surface runoff get deposited in the nearby water body such as river, lake, pond and others.  These fertilizers facilitate the growth of aquatic plants in the water body. The excess growth of plants reduces the oxygen content of the water body, which results in decline in the population of aquatic animals and foul smell in water.