Carbon Dioxide Fertilization of Marine Microalgae (Dunalliela sp.) Cultures

In this experiment, students investigate the importance of carbon dioxide to the reproductive growth of a marine microalga, Dunalliela sp. (Note that the directions are for teachers and that students protocol sheets will need to be created by teachers.)

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Teaching Tips

Teaching Tips

Educators might want to emphasize to their students that the conditions simulated in this experiment do not represent the natural environment, since, so far, microalgae in the oceans have not been shown to be CO2 limited.

The resource includes some suggestions on how to improvise seawater, nutrients and algal culture.

Since this experiment takes several days to perform, it may be helpful to have students take photographs (as in the activity description) to illustrate the changes. Take pictures or drawings of culture flasks every two days.

Students should do this experiment within the context of the ocean biological pump and its relationship to the global carbon cycle.

Students may be led to think that phytoplankton will solve the problem of too much CO2 going into the water. Thus, it is very important that teachers talk about limiting factors (nutrients, iron etc) that are critical to phytoplankton population growth. Teachers should strongly consider including a nutrient-deficient experimental bottle with enhanced CO2.

Dunalliela is not a toxic algae but if teachers feel uncomfortable with blowing CO2 into flask with a straw, they can produce extra CO2 simply using alka selzer and water in a flask with a simple tubing delivery system.