Yes, excess fertilizers and pesticides are among the many common pollutants that can degrade water quality.
Fertilizers are made of nutrients, such as nitrogen and phosphorus. When it rains, these nutrients are carried into the nearest river or other water bodies. Too many nutrients in water can cause algae to grow, which uses up the oxygen in the water, this process is called Eutrophication. Low levels of oxygen in water can adversely affect aquatic wildlife and even lead to killing of fish and other aquatic organisms.
Most of the chemical contents used in fertilizers are so poisonous that they also affect human life and whole food chain cycle. Fertilisers containing ammonia can be harmful to aquatic life if large amounts are deposited to surface waters.