It's Not Easy Being Green:    The Effect of Temperature On Algae Growth

This study investigates the effect of water temperature on algae growth rates. Students record over a period of days algae growth at room temperature, in a cool environment, and at a warm temperature. Students may work in groups or individually depending upon availability of equipment, facilities, and student sophistication. 
 
 

Teacher Notes: A most important effect of global warming would be upon the amounts and distribution of algae in the oceans. Since the Earth and oceans are both a major source of oxygen and food, any effects upon algae would have major implications for the biospere. Various species of fresh water and marine algae can be obtained from biological supply sources. This excercise uses fresh water algae for simplicity. Salt water algae can be used if salt water or a suitable substitute is available or desirable.       Since algae are photosynthetic, there is a need to supply a grow light or place the cultures in areas of varying temperatures but with sufficient light to promote photosynthesis. Unless special circumstances prevail, this may preclude using a refrigerator or incubator unless light can be supplied.       Different size flasks and amounts of culture may be used to fit your specific needs.

 
 

Unit Length:    one week

Time:   20 minutes to prepare the cultures
            10 - 15 minutes per day to take and count the sample.

Grade Level:  grades 7 - 12. Adaptable for younger students.

Materials:

Three  flasks, three pieces of foil to cover flasks, petri dish, a culture of fresh water algae, thermometer, supply of aged water (tap water that has been allowed to stand for at least three days), light microscope with a 100x capability

Procedure:

• Propose a hypothesis to test the effect of temperature on algal growth
• Obtain three flasks and three pieces of foil.
• Place water in each flask after labeling one as "cool," one as "warm," and one as "room temperature."
• Add algal suspension into each of the three flasks.
• Cover each flask with foil and place each in its appropriate environment. Be sure there is a constant and equal light source for each flask.
• Each day record growth by extracting 1 ml of the culture from each flask, one flask at a time, and counting the total number of cells in one field of vision in a 100x field. Repeat for two more fields and take an average. Be sure to record the temperature of the water in each flask each day.
• At the end of the study, dispose of the materials as your teacher proscribes.

  Analysis:
 

1. Arrange your data into table showing dates, water temperature, and the number of algae cells.
2. Describe the difference among the three test temperatures.
3. Which group could represent the control group?
4.  Plot a line graph to show cell numbers vs successive days for each temperature.
5.  Plot a "stem and leaf" for the 3rd and last days data including maximum ranges from the entire class data.

 

1. Evaluate your original hypothesis using your data; using the entire classes data.
2. Write a conclusion based on your data.
3.  How did your results compare to those of the other test groups.
4.  What effects might the cooling or warming of the upper layer of the ocean have on the overall production of oxygen? What effect would it have on the overall production of foods?

 
Extensions:
1. Propose a new hypothesis to be tested and design an experiment ..
2. What could happen if El Nino or La Nina became a permanent condition in the central Pacific or the eastern or western Pacific?
3. Research the Gaia Hypothesis and write a report or report to your class on what it proposes about the role of algae in regulating the amount of CO2 in the atmosphere.
4. Read the book Solvent Green, report to the class the premise of the book as it pertains to oceans.
 

Use the following links to help you develop innovative alternative forms of assessment.

          Concept mapping links:
           1) Lesson in teaching concept maps to students-visual included
           2) More in depth example of a concept map - detailed visual included
           3) Teacher instructions and tips

            Rubrics:
           1) Teacher Links On Rubrics
           2) Rubric Information - Advanced Secondary
 

Geophysical Fluid Dynamics Laboratory, Princeton
www.gfdl.gov

The Weather Processor
wxp.atms.purdue.edu/
 
 

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