Module 4:  Effects of Nitrogen fertilizer on microscopic plants and animals in

                   Natural waters. BACK To TOP

Introduction:  This experiment is to examine the effects of nitrogenous runoff on plants and animals in the water.  Obtain water samples from local ditches, ponds, bays, or even collected rain water that has been allowed to sit in the shade outside for a week or two.  Observe samples using compound microscope and record observations.  Perform Hach tests and then add fertilizer to the experimental container of water and no fertilizer to the control.  Observe the difference over time and record observations.  Continue observing over a period of one or more weeks and note any changes.  Observations can be done with the naked eye, compound light microscope, and the Hach test.

Materials:  For a class of 30, groups of three.  Please adjust according to class size.

1.          10 Compound light microscopes.

2.          Plenty of blank slides and cover slips.

3.            10 Hach test kits for ammonia and/ or nitrates. (optional, but recommended)

4.          Dissolved oxygen test kit. (Optional)

5.          Ammonium nitrate fertilizer and/ or milorganite

6.          Stirring rods.  Something like a popsicle stick will work.

7.          Containers, such as large cups, for each group.  Also, several large aquariums can be used for the entire class.  One cup or aquarium for each experiment and control.  If comparing chemical fertilizers to a control two cups per group would be needed.

Questions to ask, discuss, and record before beginning experiment:

1.      Discuss the effect you predict the nutrients added to the water will have?  Why do you predict this?

2.      Do you predict the nutrients will have the same or different effect on microscopic animal life and microscopic plant life?

Procedure: 

1.          Dissolve an equivalent to 1 gram per liter of chemical fertilizer and biosolid

fertilizer in separate containers.   

2.          Monitor the containers over a period of a week or longer by comparing test           

        results.

3.          Use the microscopes and Hach test kits.  Record observations.

Questions to ask, discuss, and record after experiment:

1. What effect did the fertilizer have on the animal life in the water sample?
2. What effect did the fertilizer have on the plant life?
3. How did the control compare to the test samples?
4. Based on your laboratory findings, what do you think the effect of excessive nutrients would be on a body of water similar to the one where you obtained your water sample? 
5. Graph the effects of nutrients on the growth of organisms over time.