Use a demonstration to show how oysters filter dirty water:
1 Gallon size Motts bottle filled with tap water
1 Large clear bowl
1 Strainer that will fit over the bowl
1 Small spoon
3 Spice bottles
- Oregano (to represent algae)
- Dried onion (to represent detritus)
- Peppercorn (to represent sediment)
4 Coffee filters
Hold up the Motts bottle filled with clean water. Show children how clean and clear it is. Tell them it will represent water in the bay or river.
Ask students if they think sea animals would like living in the clean and clear water.
Next, hold up each spice bottle, take off the lid and add one spoonful to the Motts bottle, explaining each time that you are adding algae (tiny plants that live in the water), detritus (tiny bits of broken down plants and animal waste), and sediment (tiny bits of broken down rocks).
After each spoonful, hold the bottle up and show how dirty and mucky the water is getting.
Ask children if they think sea animals will be able to breathe well in the dirty water.
Ask students if sunlight will be able to reach the sea animals and underwater plants. Most living things need sunlight and oxygen to survive.
Ahead of time, line the strainer with a coffee filter and add three “oysters” made out of the coffee filters. You can find the instructions for the Easy Oyster Craft here.
Place the strainer over the clear bowl.
Lift up the oysters made from coffee filters and explain that they will filter the water similar to real oysters in the bays and rivers.
Ask the children what they think will happen when you pour the dirty water over the “oysters”. Will the water be clean after it goes through? Why? How?
Pour the water slowly over the filters.
Note: If you would like some of the debris to get through, you can remove the filter that lines the strainer.
Once the bowl is half way full, hold the bowl up in the air so all can see.
Ask the children if the water is cleaner after going through the filters. Why? How? Will sea animals be able to breathe better in water with oysters?
Explain how oysters filter in a similar fashion in the bays and rivers. Let the children walk up in a line so they can see the “debris” sticking to the wet “oysters” and explain that for oysters the algae, sediment and detritus are food. Explain how oyster clean their own environment just by eating and breathing.