Carbon dioxide - Understanding Lake Data

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DISSOLVED GASES - Page 13
Carbon dioxide

Carbon dioxide (CO2), like oxygen, is affected by photosynthesis, respiration and contact with the atmosphere. It is also affected by a third reaction involving the amount of carbonate minerals, or alkalinity, present in lake water. Alkalinity is discussed in another section.

Carbon dioxide is essential to plant growth. It is the basic carbon source from which plants produce sugar and more complex organic matter. Values often fluctuate, being highest late at night and lowest early in the evening.

EQUATION 3. Carbon Dioxide Reactions.

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As carbon dioxide changes from morning to evening, so does water's pH, especially in low alkaline, productive lakes.

When carbon dioxide reacts with water, it forms carbonic acid. This in turn affects the pH (acidity) of water. Acidity regulates the solubility of many minerals.

The measure of the hydrogen ion (acid) concentration in water is called pH. A pH of 7 is neutral. Values above 7 are alkaline or basic. Those below 7 are acidic. A change of 1 pH unit is a tenfold change in acid level. Iron may also be found in high levels in acidic water.

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For more information on this topic, contact:

James Vennie
Watershed Management
(608) 266-2212

Lakes Partnership | Watershed Management | Fish Wisconsin | Fisheries Management