Materials:
- Two clear containers (jars, cups, food containers)
- Tap water
- Nitrogen: A drop of food coloring, a small amount of steeped tea, coffee, or beet juice
- Floating particles: Leaf pieces, dried grass, pencil shavings, sand, etc.
- Gills: mesh produce bag, thin dishcloth, coffee filter, kitchen strainer, etc.
- Body: Absorbent material such as a sponge, cheesecloth, rag, etc.
Introduction:
When rain washes over lawns, streets, and yards, it picks up extra nutrients (like from fertilizer or pet waste) and carries them into rivers and bays. Oysters filter water to eat plankton and in the process also trap particles and absorb some of these dissolved nutrients. In this activity, you’ll build a simple oyster model to see how mesh (oyster gills) and a sponge (body) can catch debris and soak up tinted water (simulating nitrogen). This shows how everyday actions upstream affect water quality downstream—and how oysters help keep it clean.
Procedure:
- Prepare Dirty Water: In Container A, fill with water, add a few drops of food coloring or colored liquid (represents dissolved nitrogen), and stir. Add floating particles.
- Assemble the Oyster: Place the absorbent material inside the mesh material, forming a pouch that lets water flow through but holds the sponge.
- Filter Trial: Submerge the oyster in Container A, gently move it to mimic feeding. Lift it and let water drain into Container B.
- Observe: Notice where the particles end up!
Optional Extensions:
- Compare Mesh Types: Repeat with different meshes (cheesecloth, strainer, coffee filter). Try doubling up the mesh. Note which traps more debris.
- Simulate Pseudofeces: Collect debris stuck on mesh; wrap larger bits in cotton/cloth to mimic mucus bundles, then set aside (“ocean floor”).
Accommodations:
This lesson is designed to work with many different materials. If the materials we’ve mentioned aren’t available, get creative to find similar alternatives!
