Students add fertilizer to pond, river, or estuary water and compare to a control treatment to simulate how algal blooms and dead zones occur in bodies of water.


dead zone modelStudents will understand the biological processes associated with dead zones, as well as how human activities impact the severity of dead zones. Students will also collect and plot data and use scientific equipment.



Place students in groups of 3 or 4 and assign them to bring in three bottles or jars (per group) for the lab experiment; review the concepts of photosynthesis, respiration, and decomposition.

  1. Cut the top off each bottle (if using 2-liter bottles) where the bottle tapers and remove plastic/paper covering.  
  2. Fill one bottle with tap water and let sit overnight.  Label the bottle “control.”
  3. Fill the other two bottles with pond, lake, etc. water.
  4. Add 100 mg of each fertilizer to one of the remaining bottles and mix thoroughly to dissolve. Label this bottle “dead zone.”  Label the remaining bottle “no nutrient.” Place each bottle in a sunlit window for 5-7 days.  Have the students record daily observations of the bottles, including sight and smell descriptions as well as an oxygen reading using the Vernier lab probe. The best time of day to record oxygen is in the afternoon when the algae growing reach peak net photosynthesis (see manual for how to use Vernier lab probe – do not submerge the entire probe in water). The idea is to simulate an algal bloom, or eutrophication, in which excess phytoplankton grow in response to excess nutrient input. As the microscopic algae grow, you should observe increased oxygen levels due to increased photosynthesis. Eventually you will be able to physically see increased algae as the water turns green. You should observe significantly more algae growing in the fertilized bottle, and significantly higher oxygen levels. 
  5. Plot the dissolved oxygen reading each day using a spreadsheet or by hand as in Fig. 1a.
  6. After 5-7 days (when an algal bloom has grown in the bottle), remove the dead zone bottle from the sunlight and cover with plastic wrap (if a 2-liter bottle) or the mason jar cap. Secure the plastic wrap with a rubber band and leave them in a dark place. This is meant to simulate what happens when phytoplankton in a coastal system die, sink to the bottom, and decompose, consuming oxygen. Have students continue to record data each day.  Oxygen levels should fall to a dead zone (<2 milligram per liter) as algae die from lack of sunlight and start to decompose.


Lesson Resources

Student Data Sheet

National Science Education Standards

K-12: Unifying Concepts and Processes

9-12 A: Science as Inquiry
9-12 C: Life Science