Nitrogen and phosphorus support the growth of algae and aquatic plants, which provide food and habitat for fish, shellfish and smaller organisms that live in water. When too much nitrogen and phosphorus enter the environment - usually from a wide range of human activities - the air and water can become polluted. Excess nitrogen and phosphorus cause an overgrowth of algae in a short period of time and cause what is generally known as an algal bloom. Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive.

For more information, visit www2.epa.gov/nutrientpollution