Fertilizer Runs in the River

Explore how fertilizer affects our local Milwaukee River


Students will be able to:
  • determine if the introduction fertilizers(particularly phosphates and nitrates) can affect the biodiversity of an aquatic ecosystem.

  • evaluate how the introduction of fertilizers (particularly phosphates and nitrates) can change an aquatic ecosystem in a simulated system.


What do you think?


  • Milwaukee River sample from a local stream or pond
  • 1000 milliliter beaker or large container (per group)
  • (3 per group) 500 milliliter beakers or jars to set up miniature water ecosystems
  • Dissecting microscope (2) and hand lenses (10 lenses)
  • 10% fertilizer solution in dropper bottles
  • 20% fertilizer solution in dropper bottles
  • Graduated Cylinder (for measuring fertilizer.)
  • Nitrate and Phosphate test kits
  • Petri dishes


1. Working with a partner, take a 1000 ml sample (measurement task) of the water sample from the Milwaukee River (This will be done prior to lab day)

2. Pour a portion of the sample into a petri dish and examine it under microscope

3. Provide a description of the water sample in your field journal. Use as much descriptive language as you can. (What types of organisms are found? Is there an abundance of algae and plant life?)

4. Test the nitrate and phosphate levels of the water sample.

Initial nitrate reading:

Initial phosphate reading:

5. Separate the water sample into the three beakers each of 500mL and label as follows:

  • Beaker 1-Control-no fertilizer

  • Beaker 2-10% fertilizer solution

  • Beaker 3-20% fertilizer solution

6. To beaker 1, the control, do not add any additional materials.

7. To beaker 2, add 5 mL of 10% fertilizer solution. Stir.

8. To beaker 3, add 5 mL of 20% fertilizer solution. Stir.

10. Based on the levels of fertilizer solution in each beaker, hypothesize how the organisms or biodiversity of each water sample will change. Will the organisms increase or decrease? Will the plant material and algae increase or decrease?

11. After 2 days, place a portion of each of the water samples from beakers 1, 2 and 3 in a petri dish and examine it under low and high power on a microscope. Provide a detailed description of each sample. Record your description in the appropriate column in the data table

12. Test the nitrate and phosphate level of each sample and record the number in the appropriate column in the data table

Data Table (click link)


After the observations are complete, answer the following questions in your field journal

1. Does the data collected support your hypothesis? Why or why not?

2. Based on your observations, how does the increase of nitrates and phosphates due to

the overuse of fertilizers affect biodiversity?

3. How would an increase in fertilizers around an aquatic ecosystem such as a pond or a

stream, effect the plant and animal life?

Sketch a drawing of what you found in the petri dishes