The brake-pads on cars also contain some of these metals. Brake-pad discharges runoff from roads into City streams. At higher concentrations, these heavy metals are toxic to plant and aquatic life in streams. Excessive amounts of nutrients can lead to degradation of water quality by promoting excessive growth, accumulation, and subsequent decay of plants, especially algae. These nutrients result from runoff from fertilizer use, leaching from septic tanks and sewage, and the erosion of natural deposits.
Some nutrients can be toxic to animals at high concentrations.
Turbidity is a measure of the clarity of the water. Turbidity may be caused by a wide variety of suspended materials, which is a major determinant of the quality and productivity of that stream system. Cloudiness in water is caused by the presence of suspended particles such as clay and silt. The temperature of a body of water directly and indirectly impacts several physical, chemical, and biological components of water. For example, the dissolved oxygen concentration is inversely related to temperature.