Nitrate and phosphate are useful as fertilizers in gardening and agriculture, producing more abundant crops. However, since the mass production of ammonia during the 1940's by way of the Haber process, we have known that a phenomenon called “nitrate pollution” may occur. The experiment in this lesson plan demonstrates two main ideas. The first is a test of what levels of nitrate and phosphate allow for optimum algal growth. The second demonstrates at which levels of nitrate and phosphate algal blooms may occur, causing harm to an aquatic ecosystem.

Learning Objectives

After completing this lesson, students will be able to do the following:
  1. Predict how increasing concentrations of nitrate and phosphate affect the growth of algae.
  2. Explain how algal growth affects marine habitats.
  3. Explain why observations from multiple iterations of the same experiment are necessary to draw conclusions.

Student Background

It is recommended that students have prior knowledge of algae’s ability to carry out photosynthesis. Also, students should be familiar with laboratory safety.

Science Standards

This lesson addresses National Science Education Standards (1996):
  • Science as Inquiry – Use Appropriate Tools and Techniques to Gather, Analyze, and Interpret Data 
  • Science as Inquiry – Understandings About Scientific Inquiry
  • Life Science – Populations and Ecosystems
  • Life Science – The Interdependence of Organisms
  • Science in Personal and Social Perspectives – Risks and Benefits; Environmental Quality