To maintain life, all life need oxygen, directly or indirectly.
Most warm aquatic organisms require a DO concentration above 5 mg/L.
A lack of DO will generate anaerobic conditions, resulting in unfavorable odor and visual appearance.
Transportation activities that affect Do include site DO preparation, demolition, dredging, and excavation concentrations may be altered by oil discharged from routine operations and maintenance of aircraft, watercraft, automotive equipment, and railroad rolling stock, by means of an oil film that prevents oxygen from dissolving in water.