The Algae-in-a-Bottle Experiment
W. SEAN CHAMBERLIN (firstname.lastname@example.org) is a professor of Earth sciences at Fullerton College, Fullerton, California.
The basic outline for the experiment involves a series of activities that introduce the process of photosynthesis and the factors that affect the growth of algae in aquatic environments. The instructor poses, "How can we turn this 8-oz bottle of water into an ideal habitat for marine microalgae?" Working in groups, students begin by discussing how they might maximize the amount of light in the bottle. Removal of the bottle's label reinforces students' knowledge that light drives photosynthesis. Discussions about dissolved gases lead to consideration of headspace in the bottle, and students are guided towards the realization that removing some of the water maximizes the surface area for gas exchange. Using a "recipe" provided with a commercially available sea salt mixture, students then calculate the amount of salts needed to create seawater of an appropriate salinity, a good lesson in proportions. The next step brings a discussion of the role of biologically important nutrients and their effect on the maximum biomass that may be achieved within the bottle. Various amounts of "fertilizers" (e.g., Miracle GRO) may be added to simulate nutrient availability over the seasonal cycle of a temperate ocean. Finally, after the addition of microalgae, students photograph their bottles and take fluorescence measurements (an optional step; Figure 1). Images and results are posted to Google docs. Bottles are placed under grow lights under a 12:12 light:dark cycle at high, medium, and low light intensities (simulating summer, spring/fall, and winter), and measurements are continued over a 2-3 week period. The experiment ends with student presentation of their work using Google slides.
Figure 2 below illustrates demonstrates that the ABE increased student retention and success. A survey of students after the final exam revealed that students enjoyed the experiments and felt that it was a factor in their success in the course. While definitive conclusions based on a one-semester trial would be premature, the work here suggests that incorporation of high-impact teaching practices, such as guided research, can have positive effects on student outcomes and attitudes.