The amount of free oxygen dissolved in water, expressed in mg/L, parts per million (ppm), or in percent of saturation, i.e. where saturation pertains to the maximum amount of oxygen that can be dissolved theoretically in water at a particular altitude and temperature
In biology, oxygen plays a crucial role in various biochemical and physiological processes. One of these processes is cellular respiration. The presence of oxygen makes cellular respiration about ten times more efficient in yielding ATP.1
Dissolved oxygen pertains to the amount of free oxygen that is dissolved in water. It may be expressed in mg/L, parts per million (ppm), or in percent of saturation. Saturation, in this regard, is the maximum amount of oxygen that can theoretically be dissolved in water at a given altitude and temperature.
The amount of free oxygen that is dissolved in water is measured since it can be used as an indication of the ability of a particular aquatic habitat to support living organisms living in it. It tells the amount of free oxygen that is available for organisms to use. A high or a low concentration of free oxygen in an aquatic habitat affects the water quality as well as the organisms in it.
Thus, this parameter is often measured in order to determine the quality of water and assess its ability to support life.
Water temperature, pressure, and biological activity can affect the level of free oxygen dissolved in water.
Abbreviation / Acronym: DO