Earth is the only planet known to have running water. In fact, over 70% of Earth is covered by water. All of this water is filled with life. Water is the habitat for a diverse range of flora and fauna, as well as many complex ecosystems. These ecosystems can be found in all types of water including lakes, rivers, streams, ponds, oceans and seas.

Ponds: Ponds are great for studying fresh water ecology since they are located everywhere and are usually small enough to be able to monitor easily. Ponds, like other isolated fresh water communities are composed of stagnant water. Though the water is considered fresh, it has a low ion content, the majority of which is salt. The water also tends to have suspended particles, which can give the water a murky appearance. Ponds tend to be small, shallow bodies of water with sunlight penetrating all parts. The pond environment is suitable to many different organisms. Pond life includes unicellular organisms, developing insects, plants and algae, fish (eggs and larval stages), snails, amphibians ( larval and development stages), worms, and many other organisms.

Each pond creates its own ecosystem, and in interesting to study due to the diversity of the organisms inhabiting the water. Creating ponds in the classrooms allows students to use what they learn during the field trip and subsequent activities to solve the problem of creating their own ecosystem. This activity makes the students into scientists. To create a successful mini-pond, there must be the correct combination of organisms, amount of food, chemical balance, sunlight, and temperature.A pond creating activity is outlined below, and there are also many books available providing useful information on maintaining an aquarium.

Pollution: By studying ecological relationships, scientists have been able to show exactly how pollution affects wildlife. For instance, high levels of mercury and other poisons in bodies of water are harmful to inhabitants. Ecologists have discovered that warm-blooded animals use up to 90% of their food for staying alive and moving about. Only about 10% is used for fueling the animal’s growth. For example, if an animal containing a milligram of mercury is consumed by a larger animal, it retains most of the mercury itself because it cannot easily get rid of it. However, the amount of weight the larger animal gains is only one-tenth of the smaller animal’s weight. So the mercury becomes much more concentrated as you move up the food chain. This process is called bioaccumulation or biological magnification.

A pH reading is a simple test that can indicate the quality of the pond water. Typically, ponds have a pH of 6.5 to 9.0. pH levels can change due to the acidity of rain and run off entering the pond. Acid rain is typically considered to be rain with a pH of 5.0 or less. The effect of acid rain can range from unnoticeable to almost total destruction. Some acidity of rain water is caused naturally by volcanic eruptions and lightning strikes. Dissolved CO2 in rainwater can cause a pH of 5.6. However, the type of acid rain that makes news is caused by humans.

A lake or pond affected by acid rain may have a pH of 4.5 to 6.0. A pond can usually maintain a pH flux between 6.5 and 7.5 with little stress to plants and animals. If the pH falls to 6.0 or below, a noticeable reduction in abundance of snails, amphibians, crustaceans, zooplankton, and fish occurs. Many insects and rotifers will be unaffected, while some amphibians, especially eggs, will be severely affected by even a small pH change. A pH of 5.0 will kill most organisms. Furthermore, when the pH of a pond becomes low, the effects of metals, storms, and toxins, may become more pronounced, making their devastating effects even more so.

The Scientific Method: The scientific method is used by scientists conducting research and experiments. Part of the pond science lesson is to allow the students to familiarize themselves with the scientific method. For the purpose of this lesson, the scientific method has been broken down into five simple parts. The parts are observation, question, experiment, data/results, and conclusion. Students make observations of whatever is being researched, in this case the pond. They use these observations to formulate questions. What each student thinks the answer to the question is becomes his or her hypothesis. An experiment is then set up to test the hypothesis and determine if it was correct or incorrect. The data and results collected are the evidence that answer the question being researched. Finally, a conclusion is made about the questions being asked. The conclusion usually includes whether or not the hypothesis was correct, and what the outcome of the experiment actually was.

Keeping a journal is important to this process, since the student will be able to refer back to what he or she has done and try and determine what was right, what was wrong, and exactly where any error in the results came from.

Engage: Initiate discussion about fresh water ecology by completing this pollution activity as a class. This activity is to show the effects of pollution in a body of water and wildlife. The materials required are one gallon glass jar, a measuring cup (250ml), and red food coloring. The first step is to pour a half cup of water in the gallon jar. The second step is to add two drops of red food coloring. The third step is to add one cup of water at a time to the jar until the red color disappears. It should take seven cups total to make the water clear. The red color is visible at the start of the experiment because the molecules of red food coloring are close enough together to be seen. As more water is added to the jar, the molecules of the red food coloring become further apart and invisible. Materials that are visible initially at one spot in a pond or a steam will eventually become invisible as it mixes with more water. This doesnÕt mean that the material is gone from the water. Animals can drink the water and they can be affected. This activity will allow students to start thinking about the overall theme of conservation and other ecological issues.

Preparation: Obtain materials needed for collection of organisms and water at the pond site. Obtain materials needed to create the classroom ponds. Though some will be collected at the pond, it may be necessary to purchase gravel, small fish, etc. from a local pet store. Make copies of the treasure hunt worksheet. Collecting animals and algae for the aquaria from local sources: Schedule a field trip to a local pond, stream, small pool, swamp, or lake. For the Tucson area, You can collect in streams in any number of canyons in the Catalina mountains. For example, Sabino and Bear Canyons, Pima Canyon, and Fingerrock are all good sites. Go in the spring after it has warmed up and insects are flying so that you can find aquatic insects and other insect larvae in the streams and stagnant pools associated with the streams. For example, very fun insects for tank are the yellow spotted predaceous diving beetles and whirligig beetles. Both of these eat fish food. In the canyon streams, near Tubac, or at Empire Ranch Cienega, you can find giant water scorpions - these are very active and interesting in aquaria, however, you must provide them with fish or live insects (e.g., flies) for them to eat. Another good source of aquatic insects is cattle tanks. If you are very lucky, you might find a giant water scavenger beetle; cattle tanks or other stagnant, algae-filled ponds are a good spot to find these. They are the size of very large cockroaches, but with better personalities. They eat algae (or lettuce) and will actively graze while you watch them in your aquaria. Sewage ponds do not tend to have many insects or larvae; neither does aqua caliente spring in NE Tucson. Anywhere there are lots of fish, there will not be many insects - the fish eat them!

I. Earth ball Activity
1. As a fun starting activity, have the students sand in a circle and throw a inflated earth ball to each other. As each student catches the ball, have them look where their right index finger is pointing on the earth. Is it on land or on water? Use the numbers to calculate the percentage of water on the each. Divide the number of students that are pointing to water by the total number of catches. This will be the percentage of water. The percentage should be around 75%. This activity will help students realize how much of the earth is water. This activity could also be extended, by having the students that are pointing to water decide whether it is fresh or slat water, and then calculating the percentages of each.

II. Start a scientific journal
1. Each student should have his or her own journal to write down all observations, hypotheses, and data collected.

III. Collection of organisms and pond water
A. Field trip to pond
1. Divide students into small groups to collect plants and animals. Make sure each group goes to a different location around the pond, i.e. sunny, shady, etc. Each group should record in their journals, the appearance of the site, a description of the environment around the site (including trees, grass, shrubs, etc. and their distance from the water), any pollution nearby or sources of pollution, the clarity, the turgidity, the temperature, as well as the presence of algae on the surface and at the bottom of the pond. 2. Each group should find plants and/or animals to fill out their pond Treasure Hunt sheet. A sample sheet is provided below. Animal or Plant (common name) Location Observations 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Possible species for collection include insects and larvae, tadpoles, algae, plants, small fish, worms, leeches, etc. Collected specimens will be put into vials (with water) for later observation and identification in the classroom. 3. Between five and ten students will be given gallon jugs to collect pond water for testing and to be used in classroom aquariums.

IV. Observe water samples under dissecting and compound microscopes
1. Look at organisms under the dissecting microscope. Students should from small groups (two to three) Students should draw what they can see. Students should attempt to identify the organism generally as eggs, plants, worms, other animals, etc. While looking at the organism, they should answer questions in their journals. What role does the organism play in the ecosystem? How does it function individually? What adaptations does it have? How many are there? 2. Look at organisms under the compound microscopes. The students should remain in small groups. The students should draw a variety of unicellular organisms. The students should attempt to identify the organisms using the same general guidelines. The students should also try to answer the questions above, as well as comment about the variety and abundance of the organisms. Was it more or less than expected? 3. Have each group show some of their drawings to the class. Students should say what they found, their observations, and also what area of the pond the organism was found in. 4. The teacher can describe what was found and add more information while the students are presenting their findings to the class. 5. Creative activity. Students can do this activity individually. Each student should pick an organism that he or she saw under the microscope that hasnÕt been observed previously. First allow students time to list adjectives, verbs, and adverbs that come to mind. In a poem or short paragraph, the students should compare their organism to something. It should be something that they know, so that a new object can be related to an old one. This activity will encourage creativity and writing skills.

V. Learn about pH and test the pH of the water collected.
1. Students will form small groups to learn about pH if they have not already. Students will use litmus paper to test the pH of an acid (i.e., lemon juice) as well as a base (i.e., ammonia). Each group will then make a hypothesis about the pH of the pond water. The pH of the pond water will be tested, along with the pH of distilled water, so that the two samples can be compared. The hypothesis and results will be recorded in the journal and will be used as a basis for the discussion of the health of the pond, and how the pH affects the living organisms. 2. Each group can be given a pH chart, to compare the pH of the pond water to the pH of other liquids to give them a better perception of pH. A pH chart is provided below. Strong Acid 0 Stomach 1.0-3.0 Soft Drinks 2.0-4.0 Lemon Juice 2.2-2.4 Vinegar 2.4-3.4 Cider 2.9-3.3 CowÕs Milk 6.3-6.6 Drinking Water 6.5-8.0 Eggs 7.0-8.0 Washing Soda 11.0-12.0 Quick Lime 12.4 Strong Base 14

VI. Discussion of the health of the pond ecosystem
1. Observations on the amount of pollution seen at the site, the clarity, and the pH information will be important in the discussion. Pollution indicators may include: trash at the site, trash in the water, pH below 6.5, location of the pond; is it near a factory, in a city?. Also, if organisms collected have been identified, the presence or absence of some organisms will also be an indicator of the health of the ecosystem. For example an abundance of algae nay indicate high levels of nitrogen, small or undersized organisms may mean water is not healthy, some insect larvae typically develop in more polluted water: if they are present, what conclusions can be made?.

VII. Creation of the classroom ponds.
1. Students form small groups, size depending on the number of aquariums or large bowls. 2. Each group will search for organisms and water samples at different designated areas of the pond. The type and quantity of organism added should be recorded in the journals. 3. Fill the base of the tank with aquarium gravel that has been rinsed well to discourage algae growth (mud samples can also be added to the bottom of the aquarium.) 4. Use rocks, pieces of dead wood, to create an underwater landscape and surfaces for snails to feed on, for example. 5. Add enough water to fill the tank to about half its depth. Overfilling the tank may reduce the amount of oxygen that is dissolved in the water. Water collected from the pond can then be added to the tank (this will allow the introduction of tiny animals such as daphnia. Add rooted plants in pots. The plants should be covered, but the water does not need to be too deep (1/2 to 3/4 full). Essential oxygenating plants, such as floating pond weed, can be left to float freely 6. Finally, insects, fish, bugs, and whatever other organisms have been chosen can be added. If the ponds need to be covered, a screen can be placed on as a lid, and secured with rocks. 7. Place the tanks in bright light, but not direct sunlight. The plants in the tank will grow and provide the food needed by the organisms. 8. Students should continue to observe the ponds, and record observations in their journals. During their observations they should look for changes occurring. Have any organisms disappeared? Have any new organisms appeared.? Has the abundance of specific organisms changed? The groups can compare their ponds to see the success of different models.

VIII. Join On-line pond project
1. Visit the internet site www.csis.pace.edu/schools/mv/bjackson/ourclasspond.htm. Follow the directions provided to enter information about the pond studied. There is also information about other ponds that have been adopted by classes around the world.