Answer:
Eutrophication
Step-by-step explanation:
Nitrogen is one of the nutrients that support the growth of plants and algae. Presence of excess nitrogen in water would favor excessive growth of algae in the water.
This uncontrolled growth of algal population in water as supported by the presence of nitrogen is called eutrophication. The algal population consumes available oxygen leading to lack of oxygen for other aquatic animals such as fishes.