Abstract

Objective

In this experiment you will test the effects of liquid fertilizer on an aquatic environment containing small aquatic animals and plants.

Introduction

Fertilizers are chemicals that are added to the soil to increase the growth of plants in yards, gardens, or large agricultural facilities. The effect on crops can be increased growth, but fertilizers can have a negative impact on surrounding organisms in the soil.

When a heavily fertilized field is irrigated, the water can cause the chemicals present in the fertilizer to infiltrate the ground water system. This contaminated ground water can then make its way into a nearby pond, stream, or lake. What happens to the aquatic organisms that are present in the environment when chemical fertilizers are present?

In this experiment you will test the effect of liquid fertilizer on an aquatic environment. Each aquatic environment will be a mixture of small aquatic plants and animals. By adding different brands of fertilizer, you can test how they affect the environment. Which fertilizers are the best choice for the environment?

Terms, Concepts, and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• fertilizer
• run-off
• ground water pollution
• ecotoxicity
• contamination

• How will fertilizer affect an aquatic environment?
• Will all of the organisms be affected similarly or differently?
• Which brand(s) of fertilizer will cause an effect?
• Are organic fertilizers less toxic to aquatic ecosystems?

Bibliography

• This project was adapted from the Duckweed Bio-Assay protocol from Cornell University:
  EIP, Date unknown. "Assessing Toxic Risk: Student Edition," Environmental Inquiry Program (EIP), Cornell University [accessed July 3, 2006]
  http://ei.cornell.edu/teacher/pdf/ATR/Protocol2.pdf
• At this site, you can find out the toxicity of different chemical compounds:
  Habeck, M., 2006. "Toxics," Eco-USA.net [accessed July 3, 2006]
  http://www.eco-usa.net/toxics/index.shtml
• Heavy metals are often used in agriculture as pesticides. Learn more about pesticide use and ecotoxicity from the Pesticide Action Netwrok (PAN):
  PAN, 2006. "The PAN Pesticides Database," Pesticide Action Network (PAN), San Francisco, CA [accessed July 3, 2006]
  http://www.pesticideinfo.org/Index.html

Materials and Equipment

• several brands of liquid fertilizer
• 3 gallons of distilled (bottled) water
• metric measuring cups
• pH test strips
• 6 large, reusable plastic containers with lids (6 cups / 48 oz, e.g. Glad or Zip-lock)
• permanent marker for labeling
• aquatic organisms: (should pick at least 2 plants and 2 animals)
  • small, cheap fish (minnows, feeder fish, or goldfish from pet shop or bait shop)
  • small pond snails (pond or aquarium supply store)
  • water fleas (Daphnia, available at aquarium supply stores)
  • live tubifex (available at aquarium supply stores, bait shops, or found in pond bottoms)
  • aquatic plants like duckweed or elodea (available at aquarium supply stores, ponds, or nurseries)
  • algae (spirulina, available at aquarium supply stores)

Experimental Procedure

1. Rinse each container thoroughly with water. Do not use soap because it can coat the plastic container and may be harmful to the organisms in your experiment. Label each container with a permanent marker.
2. Prepare the solutions for each container according to the data table below, one container for each experimental group. Use bottled water, not tap water, because it may contain harmful chemicals like chlorine or chloramine.

   Brand of Fertilizer	Water	Fertilizer	Total Volume	pH	Observations
   	800 mL	200 mL	1000 mL
   	800 mL	200 mL	1000 mL
   	800 mL	200 mL	1000 mL

3. Check the pH of each container with your pH test strips and record the data in your data table.
4. Evenly distribute the organisms into each container, being sure to add a mixture of plants (algae, duckweed, elodea) and animals (aquatic worms, snails, and small crustaceans). Write down the number of each type of organism you are adding to the containers. For example, "I added 10 snails,10 worms, and 20 duckweed plants to each container."
5. Observe the animals and write down observations in the data table. Continue your observations for a few hours, or overnight if necessary.
6. For each observation, count the number of organisms that are still alive for each different plant or animal. This is called a viability assay, because you are counting the number of things that are viable, or still living. For example, "At 3 PM there were 5 living snails, 2 living worms, and 7 living duckweed plants."
7. Make a graph of your results. On the left side (Y-axis) of the graph, make a viability scale indicating the number of living organisms of each type. On the bottom (X-axis) of the graph write the different brand names of the fertilizer. Then make a bar for each type of organism in your study. Did they respond similarly or differently to the fertilizers in your environments? Which products are the least toxic?

Variations

• In this experiment you tested different brands of fertilizer, but what about different amounts of fertilizer? Try an experiment making different dilutions of fertilizer in your bowls. What are the exposure limits for each of the different organisms in your study?
• Try these other Science Buddies experiments to test the effects of toxins on aquatic environments:
  • Heavy Metal
  • Acid Rain and Aquatic Life

• For more science project ideas in this area of science, see Environmental Science Project Ideas.

Credits

Sara Agee, Ph.D., Science Buddies

Last edit date: 2006-10-04 11:30:00