The Algae-in-a-Bottle Experiment: A High-Impact Learning Activity

This page authored by W. Sean Chamberlin, PhD, Professor, Earth Sciences, Fullerton College
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The Algae-in-a-Bottle Experiment provides an engaging and flexible high-impact teaching tool for helping students to know, understand, and apply a number of concepts related to the biology and ecology of aquatic plants and their environments. It is also relevant to methods being developed for the use of algae as an alternative energy source, that is, biofuels. The protocols in this experiment can be adapted use as a demonstration activity in one or two class sessions, or as a nature of science, inquiry-based activity over a few to several weeks. The easy-to-obtain and inexpensive materials used in the experiment make it accessible to institutions where resources and space are limited, as long as sunlight or artificial light are available to carry out the experiment. Preliminary results with non-majors enrolled in introductory general education oceanography courses in a community college indicate increased engagement and a high level of enthusiasm for the experiments, and suggest a better knowledge and understanding of the effects of light and nutrients on photosynthesis, and greater appreciation for the nature of science. We believe that the Algae-in-a-Bottle Experiment offers an effective means for improving science literacy and for introducing scientific research to diverse learners from middle school to college.

Learning Goals

Upon successful completion of this experiment, students will be able to write the equation of photosynthesis and explain how varying conditions of light and nutrients will affect the growth rates of microalgae and the productivity of food webs that depend on them. The level of knowledge (e.g., photosynthesis and respiration, aquatic productivty, seasonal cycles, food webs), skill (data analysis, notebook-keeping, writing, oral presentation, equipment operation), and understanding (critical thinking, synthesis of ideas, model development) depends on the degree of implementation of the experiment, that is, from short and simple to an extended and more in-depth project.

Context for Use

At its most basic level--watching algae grow in a bottle and then hatching out brine shrimp--the experiment may be suitable for third graders on up. At a college level, the experiment will introduce biology, oceanography, ecology, and environmental biology students to photosynthesis, aquatic productivity, food webs, carbon cycling, alternative fuels, sustainability, and carbon capture methods in a lecture or lab setting. The experiment has been conducted in as short as one lecture and as long as several weeks. At an advanced undergraduate level, the experiment may be used as an independent research project. Thus, the experiment is suitable for beginning and advanced students. Most of the experiment's components can be found in a grocery store. Microalgae may be ordered online for <$30. For tracking growth, students may use smartphone or iPad photography, or more advanced methods (colorimetry, fluorometry, spectrophotometry) may be used, if available. The algae-in-a-bottle experiment is highly flexible and adaptable for use in any educational setting.

Description and Teaching Materials

The topics and steps outlined in the attached description represent a sequence of discussions and activities that introduce the process of photosynthesis and the factors that affect the growth of algae in aquatic environments. The lesson plan is applicable to students enrolled in introductory biology, botany, plant physiology, algology, marine biology, environmental biology, ecology, and oceanography where a general understanding of photosynthesis, primary production, the global carbon cycle, and aquatic food webs is desired. The Algae-in-a-Bottle Experiment: A High-Impact Learning Activity (Acrobat (PDF) 1.8MB Dec22 15)

Teaching Notes and Tips

The level of complexity of each step and activity can be tailored according to the goals of instruction, or background of the instructor. The sequence may be simplified, expanded, accelerated, or slowed down depending on the time and resources available to the instructor. The entire sequence may be completed as a demonstration activity in the timeframe of a single-class, or it may be carried out as an inquiry activity over a number of classes. In the longer timeframe, each step or activity may be interwoven with a lecture or other activity, as some steps can be completed in 10-15 minutes. The longer timeframe, a kind of What About Bob? baby-steps approach, offers the greatest opportunity to achieve the highest levels of content mastery and conceptual understanding. For example, the instructor may choose to give students bottles of water that already contain algae, and ask students to observe the changes in color that appear over the course of a few days or weeks. Students may even take the bottles home to make these observations. Alternatively, the instructor may choose to cover only 1-2 steps in the lesson plan each class, permitting greater time for introduction and discussion of concepts, and allowing students to carry out individual investigations in the form of an inquiry or research activity.

The main goal here is to provide instructors with a fairly simple activity (in practice) that is fun and engaging for students, and that allows students and instructors to explore and learn about fundamental processes of global importance. Students learn best by doing, and it's in that spirit that this activity is presented.


Multiple choice for content
Google slides presentations for synthesis
Short application (what-ifs) questions for understanding

References and Resources

Culturing Methods and Information, National Center for Marine Algae and Microbiota
How to Grow Algae, Wiki-How
Measuring Salinity with a Refractometer
The Basics of Photosynthesis, Simple English Wikipedia
The Basics of Chlorophyll Measurement