Explain the problem if too much nitrogen enters an aquatic ecosystem

Excessive vegetative growth of aquatic plants and algae, Decrease in oxygen content

Explanation:

Due to substantial increase in the nitrogen content, the algal growth will be higher which deteriorates the quality of water, food resources and habitat. It can also lead to lower in oxygen content in water which affects the ecosystem making difficult for the fishes and other aquatic animals to survive. Huge algal growth may lead to algal bloom, which either reduces or removes oxygen from the water, that in turn causes illness in fishes and sometimes death in large number of fishes.