Science Junction

Water What-ifs
Temperature Mini-workshop
Introduction

T he 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.

 
Goals and Objectives

Temperature Objectives

A fter completing the tutorial you should be able to

  • describe how different factors are affected by the fluctuation of temperature levels in an aquatic ecosystem.
  • interpret temperature readings.
  • explain how to convert from the Fahrenheit scale to Celsius.
Learn the skills

Temperature



The temperature should be taken in the same area where the other water quality tests are performed. The temperature can be taken in two different ways:

 

  • Take a water sample by placing a container approximately 10 inches in depth in the water and fill to approximately 2-3 inches from the top. Place the thermometer in the sample and place in a area where it will not be disturbed. Wait approximately 2 minutes and read the temperature off the thermometer.
  • Place the thermometer in the water approximately 4 inches below the surface. Wait approximately 2 minutes for the temperature to stabilize. Remove the thermometer from the water and immediately read the temperature off the thermometer.

 

The temperature data should be in Celsius degrees. If you are using a thermometer which reads in Fahrenheit degrees, use the conversion chart to convert to Celsius degrees before adding this information to the data form.

CBL Temperature Probe (TI-83/Vernier)

  1. Press "PRGM." Arrow down until "CHEMBIO" is highlighted. (Check to see if "CHEMBIO" is loaded on your calculator. If not, use TI-GraphLink to load). Press "ENTER" and "ENTER" again to go to the title screen. Press "ENTER" to go to the main menu.
  2. On the main menu screen select "1:SET UP PROBES" and enter the number of probes being used.
  3. After you enter the number of probes being used, the "SELECT PROBE" menu will appear.
  4. Select "1:TEMPERATURE" under the "SELECT PROBE" screen and press "ENTER."
  5. After selecting "TEMPERATURE", the screen display will ask for "ENTER CHANNEL NUMBER." Always use the lowest available channel which is channel 1.
  6. The "MAIN MENU" will appear. Select "2:COLLECT DATA" to set up your experiment.
  7. Select "1:MONITOR INPUT."
  8. Monitor input by placing the probe in the sample to be tested. The temperature data will be displayed, but not recorded. The values must be recorded manually in a data table or chart.
  9. Rinse the temperature probe thoroughly with distilled or deionized water before testing each sample and before storage.
For review, click here

Check yourself

What is 35o F on the Celsius scale?

How is the rate of photosynthesis affected by an increase in temperature?

 
Post-test

Workshop Wrap-up

Once you have completed the mini-workshops, test your knowledge with the Water Quality Post-test. Once your completed post-test is submitted, you will receive a password which will give you and your students complete access to all areas of the Water What-ifs web site. Thanks for taking part in this research project on water quality.
 
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©1998-2001 April J. Cleveland for Science Junction, NC State University.
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page design by Lisa Leonor Grable and April J. Cleveland
URL: http://www.ncsu.edu/sciencejunction/depot/experiments/water/tutorial/tutorialtemp.html
Last Modified: 8//15/01

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