This Algae Bloom Decision Challenge will help your students understand how nutrient pollution, fertilizer runoff, algae blooms, producers, decomposers, dissolved oxygen, and environmental trade-offs can affect a freshwater ecosystem. This activity gives teachers an easy, NO PREP way to have students analyze ecology data, compare possible community action options, and make an evidence-based decision about how to respond to an algae bloom.

Students investigate a real-world style environmental problem in Lake Sunnyside, where thick green algae blooms have developed over several summers. Students analyze multiple Information/Data Sets related to nitrate and phosphate runoff, algae growth, dissolved oxygen levels, dead algae, decomposer activity, and possible community responses. They then use the evidence to decide whether the community should reduce fertilizer runoff, treat the lake directly, or continue monitoring before taking major action.

Students answer the question:

What action should the community take to reduce the algae bloom in Lake Sunnyside?

Students choose between three possible recommendations using information in the activity:

Option A: Reduce fertilizer runoff from lawns, farms, and nearby land.

Option B: Treat the lake directly to kill the algae as quickly as possible.

Option C: Use a phased response plan with close monitoring, public safety warnings, and clear action triggers.

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You can find this challenge as well as all my other Ecology Challenges in my Real-World Ecology Decision Challenges Bundle. Click here to see the included topics and learn more.

How It Works

• Students use the provided background reading and evidence sets to:
• Analyze nitrate and phosphate levels after rainstorms
• Identify patterns in fertilizer runoff and algae growth
• Explore how nutrient pollution can lead to algae blooms
• Analyze dissolved oxygen data over time
• Connect dead algae and decomposer activity to oxygen decline
• Explain how low dissolved oxygen can affect fish and other aquatic organisms
• Compare possible community action options
• Consider trade-offs such as speed, cost, cooperation, and long-term ecosystem health
• Use evidence to support a science-based decision

This activity moves students from background reading → data analysis → evidence comparison → final decision writing.

Topics Students Explore

• Algae blooms
• Nutrient pollution
• Fertilizer runoff
• Nitrate and phosphate
• Freshwater ecosystems
• Algae as producers
• Decomposers
• Dissolved oxygen
• Low oxygen and fish survival
• Human impact on ecosystems
• Environmental management trade-offs
• Ecosystem balance
• Evidence-based decision-making
• Real-world ecology problem solving

What’s Included

✅ Complete Algae Bloom Decision Challenge activity

✅ Student background reading

✅ Multiple Information/Data Sets

✅ Evidence analysis questions

✅ Final decision writing task

✅ Early finisher extension activities

✅ Complete answer key

✅ Grading rubric

✅ DIGITAL and PRINT ready versions

✅ Fully editable file

Perfect for:

• Ecosystems units
• Human impact on ecosystems lessons
• Nutrient pollution lessons
• Algae bloom activities
• Food web and producer lessons
• Dissolved oxygen lessons
• Environmental science lessons
• Freshwater ecosystem studies
• Data analysis practice
• Evidence-based writing
• Small group collaboration
• Sub plans or review days
• NGSS life science lessons

Teacher-Friendly Features

• NO PREP and ready to use
• Builds data analysis and evidence-based reasoning skills
• Encourages students to support claims with evidence
• Connects ecology concepts to a realistic water quality problem
• Includes built-in assessment with a rubric
• Works well for independent work, partners, small groups, or class discussion
• Includes extension options for early finishers
• Editable so you can adjust the activity for your students

This activity is a great way to help students practice analyzing evidence, comparing possible solutions, and making a science-based decision about a realistic algae bloom and freshwater ecosystem problem.