Parameter: Dissolved Oxygen             Abbreviation: DO
Classification: Physical                       Surface or Ground Water? Surface Water
EPA Priority Pollutant? No                  Is it Carcinogenic? Not Applicable
How is it Measured? milligrams per liter or mg/L    
Illinois EPA General Use Standard: 5.0 mg/L minimum

What you should know about Dissolved Oxygen:

• Dissolved oxygen is the one of the most critical characteristics of our surface waters. Fish, mussels, macroinvertebrates and all other aquatic life utilize the dissolved oxygen to breath, without it not much would survive.
• Dissolved Oxygen in streams is affected by 3 primary factors: water temperature, atmospheric pressure, and dissolved solids. Also important is the amount decaying matter in the stream, turbulence at the air-water interface, and the amount of photosynthesis occurring in plants within the stream

Major Sources of Dissolved Oxygen or Sources Which Degrade Dissolved Oxygen:

WWTP effluent and excess fertilizers from lawns and agricultural fields contribute large amounts of nitrogen and phosphorus that accelerates algae growth. Algae utilizes the dissolved oxygen during respiration at night and has the potential to remove large amounts of dissolved oxygen from the system. The break-down of dead, decaying algae and other organic materials also removes oxygen from the water

Minor Sources of Dissolved Oxygen or Sources Which Degrade Dissolved Oxygen:

Streambank erosion and man-induced activities which remove/reduce vegetation along streams and rivers increase the amount of sunlight that reaches the water. Sunlight raises the water temperature, and the water's capacity to hold DO decreases.

Typical Concentration for the Fox River Watershed:

3 - 9 mg/L. DO levels are most critical during the late summer when stream flow is low, temperature is high, saturation concentrations are low, and biological processes are increased (optimum conditions for algal growth).

Impacts to Ecosystem:

• Dissolved Oxygen is essential for nearly all life in the stream, and therefore all terrestrial/amphibian life that is supported by the aquatic life is threatened if DO levels are lowered as a result of pollution.

Impacts to Drinking Water: Not Applicable

Impacts to Recreation:

• Dissolved Oxygen is essential to sustain viable sports fishing