Oxygen saturation or dissolved oxygen (DO) is a relative measure of the amount of oxygen (as O2) that is dissolved in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor. Or it can be measured with an optode in liquid media, usually water. The standard unit is milligrams per litre (mg/l) or parts per million (ppm). Fish, invertebrates, plants, and aerobic bacteria all require oxygen (dissolved in water) for respiration. In medicine, oxygen saturation refers to oxygenation. This means when oxygen molecules (O
2) enter the tissues of the body.
- Ecology and Classification of North American Freshwater Invertebrates, eds. James H. Thorp; Alan P. Covich (Amsterdam; Boston: Academic Press, 2010), p. 32