Nutrients in the form of nitrogen and phosphorus are naturally-occurring elements in aquatic systems. In excess, nitrogen and phosphorus can have serious negative impacts on water systems and human health.
Nitrogen is a common element in all organic materials and in many inorganic industrial chemicals. Nitrogen is found as organic nitrogen (e.g. decaying plants and animals, and food products), urea, ammonia, nitrite, nitrate, and nitrogen gas. Our atmosphere contains 80% nitrogen.
Nitrogen changes forms continually in the environment following the nitrogen cycle. In biological systems such as forests, stormwater media filters, and waterways, nitrites and nitrates are continually produced by micro-organisms as organic nitrogen is broken down as a part of the nitrogen cycle.
Phosphorus occurs naturally in animal feces and decaying plant and animal matter. In a balanced ecosystem, plants can process and utilize nutrients from these sources. Nitrogen and phosphorus become pollutants when human activities such as fertilization in agriculture or large animal yards increase the nutrient load to the point where the ecosystem cannot keep pace.