Article Credit: wisconsinlakes.org
Fertilizers, leaves, grass clippings, eroded soil, and animal waste are all sources of nutrients, including phosphorus. Phosphorus is main nutrient that drives eutrophication (premature aging) in most lakes. Relatively small amounts of phosphorus can cause water quality declines. A concentration of 25 parts per billion of phosphorus in water can promote excessive algae growth in lakes.
Phosphorus—an essential nutrient for plant growth—is a common ingredient in many lawn and garden fertilizers. However, the same phosphorus that helps keep lawns green is also the primary nutrient that turns lakes green with algae. Algae blooms can turn lakes into a thick, smelly green soup that is undesirable for swimming and other recreation. Too much algae clouds water and blocks sunlight from reaching aquatic plants; it also lowers the oxygen levels in the water which can cause fish kills.
Soil can retain only so much phosphorus and plants cannot absorb more phosphorus than they can use. Spreading manure and other fertilizers on lake watershed soils already saturated with phosphorus contributes to chronic nutrient loading, as nutrients can run directly into the lake and/or leach into our lakes from groundwater for years.
Excess algae and aquatic plant growth caused by an over-abundance of nutrients can impact boating and other water recreation and increase lake management costs for lake groups.