Colored dissolved organic matter (CDOM) is the optically measurable component of the dissolved organic matter in water. Also known as chromophoric dissolved organic matter, yellow substance, and gelbstoff, CDOM occurs naturally in aquatic environments primarily as a result of tannin-stained waters released from decaying detritus. CDOM most strongly absorbs short wavelength light ranging from blue to ultraviolet, whereas pure water absorbs longer wavelength red light. Therefore, non-turbid water with little or no CDOM appears blue. The color of water will range through green, yellow-green, and brown as CDOM increases.