Cyanobacteria, also referred to as blue-green algae, is a microscopic plant-like organism that is naturally found within natural streams, rivers, and lakes. The organism thrives in warm, nutrient-rich (high in phosphorous and nitrogen) environments. Blooms occur when the populations rise rapidly, creating a large floating mass that can be bluish-green, brown, red, or yellow in color. Changes in cyanobacteria populations can be an excellent indicator of water quality.