Aquatic Pollution and Coastal Zone Managememnt (2+1)

Unit 3 : Agricultural wastes and eutrophication

3.6.What is dissolved oxygen?
Measures of dissolved oxygen (DO) refer to the amount of oxygen contained in water, and define the living conditions for oxygen-requiring (aerobic) aquatic organisms. Oxygen has limited solubility in water, usually ranging from 6 to 14 mg/l. DO concentrations reflect an equilibrium between oxygen-producing processes (e.g. photosynthesis) and oxygen-consuming processes (e.g. aerobic respiration, nitrification, chemical oxidation), and the rates at which DO is added to and removed from the system by atmospheric exchange (aeration and degassing) and hydrodynamic processes (e.g. accrual/addition from rivers and tides vs. export to ocean) .