Dissolved Oxygen

Dissolved Oxygen• The presence of

oxygen gas molecules (O2) in the water.

• It’s important for aquatic animals and plants during respiration.

• Important to note that the oxygen in H2O is not dissolved oxygen.

What’s coming out of the diffuser?

Dissolved Oxygen in the River System

• Oxygen enters a river by diffusion from the surrounding air and during the process of photosynthesis

Fast moving water dissolves more oxygen than still water

What kind of gases are dissolved in the water and in the soda?

I feel the DO.I’m doing the dew.

Water at higher

altitudes holds less

oxygen than water at lower

altitudes.

Why?

Solubility of Gases in Water

• The amount of a gas that can dissolve in a liquid is affected by both the temperature and the pressure.

How Does Dissolved Oxygen Affect the Ecosystem?

• Dissolved oxygen is critical for many of the biological and chemical processes in the river.

• It is necessary for respiration, decomposition, converting nutrients to useful forms, and converting chemicals to less harmful forms.

DO and the River Ecosystem

• All aquatic animals have some mechanism for taking in DO.

• Gills and skin are the two most common structures used for acquiring oxygen into the organism.

Different Organisms Require Different Amounts of DO

• Trout and salmon require high amounts of dissolved oxygen

• Carp and catfish can survive with much less.

How do Humans Affect the Amount of DO in the Water?

• Addition of oxygen-consuming organic wastes

Addition of Nutrients

Changing the Flow of the Water

Which dam is this?

The Croton Dam

Activities That Raise the Water Temperature and

Decrease D.O.

How is Dissolved Oxygen Measured?

• Dissolved oxygen is measured in mg/L (ppm) or % saturation.

• Explain saturated, unsaturated and supersaturated

Would the time of day affect the amount of DO in the water? Why?