2.8. JUST A PINCH
(Level: 10 acad : 11 acad :: Water Quality)

Purpose: To observe the effects of excess nutrients on an aquatic ecosystem.

What You Need: 2 2-litre jars :: pond water (2 litres) :: 6 strands of coontail, fanwort, or Canada waterweed (10-20 cm long) :: lawn (or other type) fertilizer

What You Do:

1. Fill both jars with pond water.
2. Add half of the aquatic plants to each jar.
3. Label one jar "Control" and the other jar "Experimental"
4. While wearing gloves, add and dissolve a few granules of lawn fertilizer in water. (CAUTION: Too much fertilizer will kill most life in the jar.) Add the solution to the experimental jar.
5. Place the jars side by side in a bright location.
6. Observe the jars each day for 2-3 weeks. Make notes on changes in the appearance of the aquatic plant, and the rest of the ecosystem.

Questions:

1. What are the producers in your ecosystem? (If needed, see notes in "Ecology Module")
2. What important invisible organisms are in your ecosystem?
3. What is the purpose of the control jar?
4. Describe the changes the fertilizer caused in your ecosystem. Explain these changes.
5. Explain why sewage and fertilizer runoff can cause plant and algal growth in an aquatic ecosystem.
6. Explain why we try to prevent fertilizers and excess nutrients from entering wetlands.

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Extension:

1. Filled labelled jars with samples from ponds known to have enriched waters (such as farm ponds, rivers) and compare the growth to a control jar of tap water. Plant growth is used as a "bioassay" of nutrient content.

What You and Your Family Can Do to Help

• grow plants that are suitable for your locality and that do not require fertilizer
• do not use of fertilizers
• if the circumstance arises where you must use fertilizers, use them only in the quantities recommended or, better still, in many cases, you can use a weaker solution
• if you live on a farm with livestock make sure your know how to manage your manure pile to prevent excess nutrients from reaching nearby wetlands and limit your livestock's access to wetlands (contact the Ministry of Agriculture or other agencies for further information).
• communities - build storm retention ponds to hold run-off and allow for the slow release of water and nutrients to water systems

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