Water Holes to Mini-Ponds

Observe and compare changes that take place in unfertilized and fertilized water holes. This activity requires regular visits to monitor the water holes for eight to ten weeks.

Group Size: The construction part of this activity works best with small groups. Large or small groups can study the water holes once they have been set up.

Suggested Age:

Time: 40-60 minutes to set up water holes and 15-20 minutes for each subsequent visit: twice a week for eight to ten weeks, if possible.

Consider…
Site: Select a level spot that receives direct sunlight and is near a water tap. Avoid placing the water holes at the base of a slope (runoff can be a problem) or near resinous trees such as pines or eucalyptus. The site should be conveniently located but relatively safe from vandals.

Safety: See Survival Kit/Aquatic Safety

Materials/Prep: rigid plastic containers (1m across, 30cm deep), burlap to line pools, access to water, observation aids,

Focus question:
What are the major differences between fertilized and unfertilized water holes?

• participants identify organisms that

Summary:
Dig a hole, line it, fill it in with fresh water, and you have a water hole: a good place to study colonization. Colonization is the organisms that did not previously life there. The process of colonization involves:
- immigration of organisms
- suitable conditions for survival (sufficient food, proper light and temperature).
- population increase (reproduction, immigration of more organisms).
- population decrease (organisms eating other organisms, emigration or death of organisms)
The appearance of life in a water hole transforms the baseing of water into a mini-pond.

To provide a fair comparison of the effects of fertilizer on a water hole, two water holes are set up that are identical except for the addition of a handful of fertilizer to one water hole. This fair comparison is called acontrolled experiment because all factors (variables) that can vary (such as location, shade, wind, water level) are controlled or kept the same with the exception of the one factor (fertilizer) under investigation.

What to Expect
You can expect your water holes to support a number of plants and attract a variety of animals. The major factors affecting the variety and number of organisms are:
- the time of year. (warm seasons are best.)
- the amount of time the alter has been standing. (The longer the better.)
- the proximity of the water holes to a pond, lake, or stream. (Close proximity to established populations speeds colonization.)

The following is a summary of events that occurred in a pair of water holes set up on the West Coast during the spring and summer months. The water holes (a control and one to which one-quarter of a liter of lawn fertilizer had been added) were set up side-by-side in full sunlight near an established pond. Tap water was used to fill the water holes and maintain their water levels.

For the first eight weeks, the life in the fertilized water hole was more varied, more numerous, and grew faster than life in the unfertilized water hole. The fertilized water hole turned green from heavy algae was set up. The unfertilized water hole never turned green from excess algae growth. More life probably appeared in the fertilized water hole because the fertilizer added minerals that enabled algae, the basic food source, to grow faster.

In the ninth week, the green algae in the fertilized water hole suddenly died and settled out as a foul smelling scum. All insects except mosquito wigglers and flower fly larvae disappeared from the fertilized water hole, and tubifex worms colonized the bottom scum. The unfertilized water hole continued to support a variety of pond organisms until the end of the experiment.

Extension Activities:
Continuing with the concept of a controlled experiment, other experiments to conduct with the water holes are:
- Use other water holes to test the effects of different variables, such as detergent, oil, sugar, or salt, and observe and compare the changes.
- Monitor the dissolved-oxygen content of the water (if you have a test kit available).
- Add predators (fish, crayfish, dragonfly nymphs) to the water holes and watching what happens
- Connect the ponds with a piece of water hose (filled with water) or a small canal to see if any of the organisms migrate from one pond to another.