Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern. Nutrient pollution occurs when there is an overabundance of nutrients (such as phosphorus and nitrogen), which when increased within the water sources operate similar to fertilizers and produces high concentrations of algae. Urban areas are greatly affected by nutrient pollution as these nutrients have a tendency to run off of lands into gardens and lawns, which are generally found in urban sections.