Science Junction

Water What-ifs
Water Quality and Temperature

Temperature Reference Desk
 * Teacher Notes, Lesson Extensions and Alternative Assessment Ideas
 * Temperature Scales and Conversions
 * Warning Signs of Pollution
 * Using Lamotte water quality test kit
 * Using CBL equipment

The temperature of an aquatic ecosystem is of great importance because it can influence:

  1. dissolved oxygen levels;
  2. the rate at which algae and aquatic plants photosynthesize;
  3. the metabolic rates of aquatic organisms;
  4. how aquatic organisms are affected by different pollutants, parasites and pathogens.

Since cold water can hold more dissolved oxygen than warm water, one of the man-made problems associated with water quality is thermal pollution. Thermal pollution is the introduction of warm water or other substrates into an aquatic ecosystem. Sources include industries such as power plants and also storm-drain runoff which has been warmed on streets, parking lots and sidewalks.

In addition, human activities such as cutting down trees, the removal of vegetation around the water, and construction can lead to an increase in water temperature. These practices can cause an increase in erosion which leads to an increase in dissolved solids in the water. As dissolved solids increase, the water becomes turbid or cloudy which allows the absorption of the sun's rays which increases the water temperature.

Increases in temperature also cause changes in aquatic plants and animals. As the temperature increases, the rate of photosynthesis increases. At temperatures above 32 degrees Celsius, the rate of photosynthesis will start to level off and then begin to decrease as the temperature continues to increase. As photosynthesis increases, the number of aquatic plants increase. This can lead to an increase in the number of plants which die and are decomposed by aerobic bacteria which consume oxygen in the process.

Increases in temperature also increase the metabolic rate of organisms which live in aquatic ecosystems. As the metabolic rate increases, the demand for dissolved oxygen increases and the rate at which the organisms go through their life cycles increases. As their life cycle rate increases, they may not be available as a food source at specific times as needed by many migratory species.

Temperature Lessons 1, 2, and 3 are intended for middle school and high school science students. These lessons focus on the effect on different factors due to fluctuation of temperature, the effect of temperature on aquatic plants, and the effect of temperature on brine shrimp eggs.These lessons highlight several aspects of the following competencies:

Lesson1 Does a fluctuation in temperature effect the growth and survival rate of aquatic plants?
Lesson 2 How is the metabolic rate of clams effected by a change in temperature?
Lesson 3 What is the Optimal Temperature for the Hatching and Development of Brine Shrimp Eggs?

Download PDF version of all three temperature lessons.


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Last Modified: 2/24/00

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