Dipping Into A Pond's Ecosystem

By Eve Pranis

"My inner-city first graders had little experience with and access to wildlife or habitats," reports Terre Haute, IN, teacher Todd Warren. But that didn't stop them from hatching ideas and questions about what forms of life they might like to see in their small courtyard.

"When the idea of building a pond came up, the kids brainstormed what they already knew about ponds and pond life, what they'd like to learn, and what they would like to see in their own watery habitat," says Todd. Frogs, turtles, and plants topped the list. So began the planning for a two-level pond, which became the centerpiece for science investigations, journaling, and media projects throughout the year.

Eyeing a corner of their small courtyard, students first estimated, then measured the amount of space available. "They were so eager to get going I went out that night to buy materials," says Todd. With just $109 from a small grant, Todd got a hard plastic liner, pump, and hoses from Sam's Club. (Later, a request to Wal-Mart yielded donated tools and materials for a retaining wall.)

"Once the liner was in place, the students estimated how much water it would take to fill each level," explains Todd. "But when they began to carry out buckets, one by one, they realized they'd need to seriously revise their estimate!" The 35-gallon top level spills into the 125-gallon bottom level, where it's pumped back up. "The movement oxygenates the water and keeps it from freezing, so the fish can manage through the winter," says Todd. They also installed a natural filter above the ponds using a garbage can, lava rocks, sand, and aquatic plants. The rocks and sand filter out some of the larger debris and harbor beneficial bacteria. The plants absorb nitrates, which would otherwise cause algae to proliferate.

Plant books, catalogs, and a video on pond life sparked students' thinking about what types of organisms would be appropriate to their environment. They started with some donated water plants, then purchased a few goldfish and catfish. Next, the real fun began. Students scoped out local ponds and brought back bullfrogs, tadpoles, native plants, and other potential pond denizens. The principal even donated a 3-foot-long iguana, who resided in the courtyard and took occasional dips!

Students illustrated journals describing what they'd put into the pond, what was happening, and what discoveries they'd made. "The kids used hand lenses and a microscope to investigate a dragonfly nymph, snails, and other life forms they assumed had arrived with plants they had imported," says Todd. Twice a month, his young scientists measured representative plants and fish, checked for new growth, and noted water levels. "The kids were surprised to discover how quickly plants grew," explains Todd. Noting that the algae, in fact, flourished, the pond stewards yanked some of the green scum to keep it from getting out of hand.

With an eye toward comparing their pond to a real pond, Todd's explorers took a field trip. Their discoveries? The natural ecosystem was bigger, "dirtier," and more populated with animals, including the microscopic variety. "By having a small, accessible ecosystem, students began to grasp the concept of habitats, plant/animal interactions, and life cycles," says Todd. "They also understood the idea that death and decomposition can help other things grow." How did he know? When a fish died, the students suggested planting it next to a tree to provide nutrients for growth.

More Pond Investigations

  • Challenge students to figure out how to determine the pond's volume (in milliliters, liters, and/or gallons).
  • Estimate population numbers of selected plants and animals, then create a graph. Note population changes over time.
  • Explore pond organisms up close using hand lenses or microscopes. Have students draw and describe them, noting their methods of movement (or how they are rooted), food sources, life cycle changes, and so on. What types of features might help pond life adapt, compete, or survive?

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