Lesson 4 - SDG - Life Below Water: Design and Build a Coral Bleaching Model
1. Engage: What will happen if a coral reef changes color?
Imagine snorkeling in a tropical ocean bay last summer—you swam through a rainbow of coral: bright pink branches, golden brain-shaped mounds, and neon blue clusters, with fish darting everywhere. This year, you return to find the reef pale white, and almost no sea life in sight.
Show students images of the reef from last year and today:
Key Question
What changes over these years?
The coral reefs turning white which is called coral bleaching.
2. Explore: What is coral bleaching?
Review the symbiotic secret behind coral health:
Healthy corals get their color from algae, which provide most of the coral’s food using sunlight. Corals also produce their own bright pigments that add pops of pink, blue, or purple to their appearance.
But when corals are stressed, they expel the algae. Without these algae, corals lose their color and turn pale white.
Fun Fact (from NOAA): Corals can survive short bleaching events if the stress is removed (like if ocean temperatures cool down), and the algae may return. But if stress lasts too long, the coral starves and dies.
Today, we’ll use an LED strip and waterproof temperature sensor with our micro:bit to simulate both vibrant healthy corals and bleached reefs—and even "revive" them with code!
3.Investigate: What causes coral bleaching?
Activity 1
In groups, students use safe websites to research causes of coral bleaching.
Coral bleaching can be caused by many factors, such as change in ocean temperature, runoff and pollution, overexposure to sunlight and extreme low tides.
Today, we’ll use the micro:bit with LED strip and a waterproof temperature sensor to build a coral bleaching model that shows how corals turn white when ocean temperature changed.
4.Design: Draw a flowchart of the rules for coral color changing
Answer these questions and draw a flowchart for coral color change rules:
1.What will trigger bleaching? (e.g., temperature sensor reading above 29°C)
2.What does healthy coral look like in your model? (e.g., orange)
3.What does bleached coral look like? (e.g., white)
4.Do corals turn white all of a sudden?(e.g., they change slowly over time)
Activity 2
Guide student complete the flowchart on the activity sheet.
Example Flowchart:
5.Build: Assemble the model system
Guide students to read the building block assembly steps on the activity sheet, and assemble the building blocks under the guidance of the sheet.
Activity 3
Give students 5-8 minutes to complete the assembly of the building blocks by following the activity sheet.
6.What’s next?
Preview of next class:
1.Write the program
2.Debug the code
3.Test the project
4.Decorate the model
5.Complete the project
Lesson4.zip 
