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Reef Indicators Lab
University of South Florida, St. Petersburg
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The Coral Reef Cake: An Activity for K-12 Earth Science or Biology Classes

Suggested Slide Presentation for use with Coral Reef Cake Activity
HTML  PowerPoint  PDF

Slide Show of Coral Reef Cake Activity in progress
HTML  PowerPoint


Coral-Reef Cake is an interactive activity that will ignite student interest in what science is: a fun, uninhibited process of discovery. The exercise begins with a short slide presentation. Pictures of coral, coralline algae, sea grass, sea fans, sponges, sea urchins, and fish introduce the students to important players in the reef story. A volunteer "scribe" records the names of each plant and animal group. An underwater coral-reef photo, followed by an aerial view of a reef showing spur and groove features, provides the backdrop for a brief discussion of reef zonation, from the deep reef to the reef crest to back-reef seagrass beds. Bioerosion is described using a cartoon of a parrotfish eating coral and defecating sand.

Then the food-enhanced learning begins. A large, flat cake is brought out (one cake mix baked in an oversized pan), as well as a tray of the "reef creatures." The cake is tilted towards the students, to represent shallow to deep reef. Two student volunteers are provided disposable gloves and are instructed in how to assemble the pieces, as the student scribe writes down what reef creature each food represents. The flat yellow cake represents the Key Largo Limestone, which is the substrate upon which a Florida reef grows. For an island reef, a chocolate cake can represent volcanic substrate. The cake is covered with pink frosting, representing coralline algae that encrust and hold the reef together. Green-tinted coconut becomes a seagrass bed in the backreef. The reef itself is made of stick pretzel "branching corals," muffin "brain corals," and bite-sized cookie "plate corals" arranged in linear spurs. Frosting sprinkles provide the sand. Corn-chip "sea fans", marshmallow "barrel sponges", and chocolate chip "sea urchins" are placed in the seagrass bed and around the reef. Fish-shaped crackers or candies mounted on toothpicks swim in schools around the reef. After a review of the reef components, the class "bioerodes" the reef and soon there is nothing left except smiles and a few crumbs.

Coral-reef cakes have been constructed and bioeroded by elementary children, 8th/9th grade science-campers, and high-school marine biology classes. Groups of less than 20 are ideal; the time needed is 30-40 minutes. Artistic results should not be anticipated!

Essential Steps for a Successful Reef Cake Activity

A. Well in Advance of the Activity

  1. Prepare the instructional material (i.e., slide show, access website, etc.)
  2. Make sure desired visual aids are available (i.e., slide projector, chalkboard, etc.)
  3. Make sure a table is available at the front of the classroom
  4. Purchase ingredients (creativity and imagination recommended) (Ingredient List)
  5. Purchase or assemble other necessary items (Other Necessary Items)

B. Evening or Morning Before Activity

  1. Bake the flat cake in an oversized pan like a broiler pan or turkey roasting pan
  2. Bake or purchase muffins or cupcakes and bite-sized cookies
  3. Assemble ingredients and equipment 
    • Color coconut and marshmallows
    • Place reasonable amounts of each ingredient into an appropriate-sized plastic bag or container
    • Fish can be placed on toothpicks in advance or by students
Ingredients for the Reef Cake:
  • Yellow or chocolate sheet cake baked in an oversized pan (1 cake mix) representsKey Largo limestone (yellow) or volcanic rock (chocolate)
  • Pink frosting (1 package) represents Coralline algae
  • Pretzels or other stick-shaped food (handful) represent Branching corals
  • Muffins or cupcakes (6) represent Brain corals
  • Bite-sized cookies (less than 10) represent Plate corals
  • Green-tinted coconut (handful) represents Seagrass
  • Brown-tinted marshmallows (4-6) represent Barrel sponges
  • Corn chips (snack pack or 6-8) represent Sea fans
  • Sprinkles (1 bottle) represent Sand
  • Fish-shaped crackers or candies on toothpicks (~10) represent Fish
  • Raisins or chocolate chips (5-10) represent Sea urchins
Other Necessary Items:
  • Plate or tray and plastic bags to hold items prior to assembly of the reef
  • Spatula or plastic knife to spread the frosting and cut the cake
  • Disposable rubber gloves to be worn by anyone handling the food
  • Paper plates, napkins and plastic forks for the "bioeroders"
  • Toothpicks to mount the fish upon so they can "swim" about the reef
  • Four-color pack of food coloring
  • Box and grocery bags to carry items
  • Disposable table cover or clean cloth table cover
Classroom Equipment Needed:
  • Slides of a coral reef and reef organisms, slide projector and screen, or pictures of a reef and reef creatures, or a computer with internet access to view website
  • Chalkboard or other means for students to see or make a list of the reef components
  • Table upon which to assemble the cake

C. Setup for Activity in the Classroom

  1. Check location and operation of visual aids
  2. Check for chalk or writing-board pens
  3. Make sure a clean table is available for the exercise
  4. Organize the food items
    • Place on one or two trays and set aside, preferably covered, to avoid distracting students
    • Alternatively, if bagged individually, they can be held up and discussed as they are pulled out of the grocery bag prior to cake assembly

D. What the Students Need to Know: Slide Presentation

  1. Assign a "scribe" to write down key reef names and food proxies
  2. Show the slides (HTML or PowerPoint), pointing out key features and inviting student participation

E. The Reef Cake Assembly

  1. Ask for volunteers, or appoint students
    • Two to assist with assembly of the reef
    • Optional: Two to assemble the fish schools on toothpicks
  2. Bring out the table and table cover
  3. Bring out the bags or trays of equipment and ingredients
  4. Open bag of disposable gloves
    • Put on a pair
    • Hand a pair to each student assistant
  5. Assemble, identify and organize ingredients
  6. Give the toothpicks and fish crackers or candies on a plate to fish assemblers
  7. Orient the cake with the longest dimension facing the students
    • Explain that the cake represents the rock upon which the reef has grown
    • Tilt the cake pan towards the students
    • Explain that the backreef is towards the assemblers, the forereef is towards the class
  8. Instruct students in assembly, identifying each ingredient and what it represents
    • Cover the cake with pink frosting representing coralline algae that binds the reef together
    • Assemble the seagrass bed, with seafans and barrel sponges, in the backreef
    • Create a branching-coral thicket just "seaward" of the seagrass
    • Place two "spurs"of brain corals and plate corals
    • Shake the sand "sprinkles" over the reef, especially in the grooves between the spurs
    • Place sea urchins (raisins or chocolate chips), explaining that they like to hide in the reef and seagrass
    • Barrel sponges and sea fans may also be placed on the deep reef seaward of the spurs
  9. Invite the fish assemblers to place their fish on the reef
  10. When the reef is complete, review each step and key detail

F. Bioerosion of the Reef Cake

  1. Review what bioersion is on the reef
  2. Cut and distribute cake
    • Use either the present group of student volunteers or provide other students with gloves
    • Students will volunteer their preferences, especially regarding coconut

G. Cleanup

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