Dissolved oxygen is oxygen dissolved in water and is as important an environmental indicator as pH when measuring the water quality of rivers and lakes.

Dissolved oxygen (hereafter abbreviated DO) is oxygen (O2) dissolved in water in nature in proportion to the partial pressure of O2 in the atmosphere. Dissolved oxygen content is expressed as the amount of dissolved O2 per unit volume of water (mg/L).

Fish and other organisms in water live on the oxygen content. DO content is affected by water temperature, salt concentration, atmospheric pressure, and other conditions, and the saturation level decreases as water temperature increases.

Therefore, in rivers with high organic pollution, the death of aquatic life due to oxygen deficiency often occurs in hot summers.

In recent years, therefore, the amount of dissolved oxygen in culture solutions used in cell cultures has been controlled.