Blue-green algae, technically known as cyanobacteria, are microscopic organisms that are naturally present in lakes and streams. Under certain conditions, blue-green algae can become abundant in warm, shallow, undisturbed, nutrient-rich surface waters that receive a lot of sunlight.
A combination of warm temperatures, sunlight, and nutrient-rich waters can cause blue-green algae to reproduce rapidly, or "bloom." Within a few days a clear lake, pond, or ditch can become cloudy with algae growth. Blue-green blooms usually float to the surface and can be several inches thick near the