When there is excessive nitrogen then it will have negative effect on aquatic ecosystem because of the over nutrition in aquatic system.
Explanation:
Nitrogen will drain away from soil and make the concentration of nitrogen high in water.
This harms aquatic system by excessive growth of algae which will over shows the water surface and eventually block sunlight which is require for another aquatic organism.
When those algae die, during decomposition, oxygen is consumed which will deficit oxygen for other organisms.
