Students measuring algae eaten


Aquatic Foodweb

Grades: Target grades 5-8 can be adapted for grades 2-4

Group Size: 12-30

Maine Learning Results
Grade Level 5-8
B: Ecology #2. Finite resources limit populations
# 4. Ways organisms interact (predator, prey )

Duration: 1 -2 hours

Location: Inside or outside


  • Information about organisims in a fresh water food web.
  • split green peas and lentils for algae
  • small plastic baggies with a sketch of zooplankton in sharpy marker
  • Small and medium paper bags and markers/crayons OR pre made DEP fish using 3 " net covered with cloth and the handle is the backbone for a planktivorours fish. 8" net covered similarly for the pisciverous fish.
  • Measuring cup or graduated cylinder and funnel
  • Dust pan and broom

Introduction (5min)

Assess student knowledge. Keep a list of vocabulary. Hand out worksheet.

Ask these questions:
What is a food web? Describe what it looks like- could have student draw on board or have students draw a lake food web on the back of the worksheet.
Possible prompts: What is the base of a lake food web, primary producer? (Sun Supported Plants). What types of plants are in lakes? What happens to the food web when we pollute?


Activity 1- Explore how nutrients and other pollutants can enter a lake. (15-25 min)

Use the Enviroscape watershed model. Soil is the number one pollutant to lakes, and it brings nutrients to feed the base of the food chain. You can help prevent lake pollution by the actions you take.

Activity 2- Identify Organisms

Introduce worksheet and tell students they have to identify and name the organisms on the worksheet as they learn about them as a class, or by cycle around the stations.

Algae (5-10 min) Overview of algae. Understand small size of individaul alga and environmental impact of algae blooms. Look at pictures of blooms and microscopic organisms on web or under microscopes.

Zooplankton ID (10-15 min)
Learn the different types of zooplankton using web sites with video clips, ID key, microscopes, or projection of real organism. Draw two zooplankton on a plastic baggie with a magic marker. If doing stations, or there is additional time do activity Design a Plankton.

Macroinvertebrate ID (10-15 min) optional
Using live specimens or pictures, identify macroinvertebrates and learn what they eat to see where they fit in the food web. Draw two macroinvertebrates on baggies.

Fish ID (10- 15 min)
Look at Inland Fish and WildLife's web site for posters of fish in Maine. Introduce vocabulary: predator- prey relationships, Planktivores (eat plankton could be called an herbivore on land), Piscivores (eat other fish could be called carnivore on land), and Omnivores (eat small fish and plankton). Show DEP fish puppets used for the game, or have student make their own fish by drawing fish on different sized paper bags.

For a hands-on way to learn more about individual fish, do the following fishing activity. Place laminated fresh water fish cut out from MEIFW poster of warm water and cold water fish. Attach paper clips to the fish and place them in a box or on a tarp to represent a "lake". Give students pretend fishing poles (some type of short stick with a magnet on the end of string). Allow students to catch fish. When they catch a fish, they should use the book published by MEIFW called "Fishes of Maine" to determine the eating preference of the fish and whether it is invasive or native.

Discuss- Movement of energy through the food web. Lake management Top Down or Bottom Up? Brief discussion

Activity 3- Food Web Game. (15-20 min)

Explain this is a model of the real world. Walking only, don't want to step on any zooplankton's hands!

First chose the majority of the students to be zooplankton. Each zooplankton has two baggies, one on each hand. Depending on the scenario, there will be between 4 and 8 planktivore (fish) and 1 -4 piscivores (fish). The amount of split peas would depend on how much pollution or nutrients are available in the water.


Student on right is a zooplankton eating algae (split peas).  Student on left is a piscivorous fish eating zooplankton.

Playing the game

Establish an area that will be the lake. It should be easily swept up. It could be done in an open space, or in the classroom with desks serving as rooted plants, but this may be a source of injury if students get too wild.

Discuss how much sunshine has been on the lake and what degree of pollution is entering the lake to determine how much algae to add. Spread a measured amount of split peas on the floor. (You may need to experiment with how many peas are needed for how big of a space.)

The Zooplankton Players - Each person has two baggies. They pick up the split peas and put them in the baggie as if it were the zooplankton's stomach. If macroinvertebrates are part of the lesson include them in this round.


The Planktivore Players - This part of the activity is played like tag. The planktivore uses the mouth of the net to scoop up or tag one zooplankton or macroinvertebrate from each person. If the mouth of the fish touches the plastic bag of the zooplankton, the zooplankton gives the baggie up with the peas inside. The zooplankton or macroinvertebrate starts filling the other baggie. The planktivore puts the baggie in its mouth and continues to pursue other zooplankton. Eventually, a planktivore's stomach may fill up. If this happens, they no longer eat. They just rest and digest.

The Piscivore Players - Similar to the tag game played by the planktivores, the piscivores pursue the planktivores and swallow the entire fish net in their stomach. They too eventually fill up their stomach.

The Omnivorous Fish - They can eat zooplankton, macroinvertebrates, or small fish.

The zooplankton and macroinvertebrates start eating first for 20 seconds, and then the planktivorous fish are released into the pond from separate sides of the room. Twenty seconds later the pisciverous fish are released. The round should last one minute. Make sure each round is the same length of time. After the round ends, have the students observe how much algae is left in the lake, then do stomach content analysis (measure the split peas that have been consumed). Make a data table to record the amount of algae consumed along with the number of zooplankton, piscivores, or planktivores who played this round. Have students fill out the results on their worksheets.

Repeat the game changing roles and adjusting the number of planktivores, piscivores, zooplankton, and even algae.

Round 1 -7 planktivores, 1 omnivore, 1 piscivore
Round 2 - 4 planktivores, 2 omnivores, 2 piscivores

For variation, you could do more rounds with different combinations of organisms and algae. Record the results for each round.

Closing (5-10min)

Review and debrief what was learned. Review vocabulary. Analyze and discuss how the different rounds affected the amount of algae. Discuss top down or bottom up management. Discover that it is both. Talk about how they can make a difference- reduce runoff, not introduce invasive species of fish, catch and release depending on species and in accordance with regulations. Ask what you can do to protect the lake food web. Have each student name one action. For older groups, explain the research called Biomaniplutation, about the Cladoceran size, water clarity, and how this is currently being researched in East Pond in the Belgrade area.