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Chesapeake Bay

Activity 5 (Explain): Where is the Pollution

Coming From?

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Activity Overview

Activity Summary

In this short activity, students study an infographic to learn that the main source of nitrogen pollution to the Bay is from agriculture and air pollution. They use this new information to help understand where the algae bloom came from.

Activity Objectives & Materials

Approximate Time: 30 minutes​


  • Students will be able to name the primary sources of nitrogen pollution to the Chesapeake Bay


  • Computer & projector


  • Where is the Pollution Coming From?

Timing Tip: Because this activity is on the shorter side, it works well on a day when students are also making observations of their Algae in a Bottle experiments.

Standards Connection

DCI: ESS3.C: Human Impacts on Earth Systems

CCC: Cause & Effect



What do plants need to grow?

  • The purpose of this warmup is to start laying the groundwork for students to make the connection between nutrient pollution and algae blooms. They will likely say things like water, air, sunlight, and soil. During the warmup discussion, ask students what plants need from the soil. If they don’t know ask them if they’ve ever grown a plant or know someone who grows vegetables or flowers. Ask what they put on the soil to help their plants grow? (fertilizer). Students will discover some additional information about this later in the activity, so don’t give away too much at this point. The goal is just to help students start making this connection.


1. Frame the Activity

Return to the clues board that you’ve been developing about the what killed the fish in the Bay. So far you should have at least these three clues (or something similar to them):

  • Dead fish in the Chesapeake Bay

  • Lots of algae appeared in the Bay before the fish died

  • When there is too much algae, they die, and the amount of dissolved oxygen goes down

Ask students if they think they can solve the mystery of what caused the fish to die. Have them turn to a partner to share what they think happened. At this point, students should be able to explain:

  • The fish died because they didn’t have enough oxygen to breathe (they suffocated). There was too much algae from the algae bloom so when the algae died and decomposed, the decomposers used up all the oxygen, so there wasn’t enough for the fish.

If all students haven’t quite reached this stage of articulating an answer, it is okay, because they will have additional time in the future. As long as some students can reach this point, tell them that

they’re close to solving the mystery, but there’s still at least one more question they need to answer: Where did all the algae come from? Tell them that during class today they’re going to begin investigating that question.

Step 1

2. Fiendish Fertilizer

Remind students that one of their “I wonder” questions from the Chesapeake Bay video was about pollution in the Bay. Tell students that there are four main kinds of pollution that enter the Chesapeake Bay: toxic chemicals, nitrogen, phosphorus, and sediment (ex. sand). Go through each one, and ask students whether they think it could have caused the algae to grow into a bloom. Use questions to help them remember that nitrogen and phosphorus are in fertilizer (they should be able to remember this from their algae experiments). Help them reach the conclusion that nitrogen and phosphorus are likely what is causing the algae to grow.

Timing Tip: If students are already into Week 2 of their Algae in a Bottle experiments, they may have an idea of where the algae came from. Tie this in as much as possible to help students make the connection between the algae bloom and nutrient pollution.

3. Where is the Pollution Coming From?

Ask students where they think the majority of this pollution is coming from? Acknowledge students’ responses, but don’t give away whether they are right or not. Next, hand out the “Where is the Pollution Coming From?” sheet for students and have them use the infographic to answer the questions.

Note on Source Data: The information in this infographic is constantly changing due to changing human behaviors and land use. Scientists like Lewis Linker (our Air Quality Champion for this module) create models to better understand all the nutrient inputs into the Bay to better understand the source of the problem. While more updated percentages may be available, the general sources of the pollution have not changed significantly.

Nitrogen pollution infographic.jpg

Afterwards, lead a short discussion to ensure students understand the key takeaways:

  • The majority of nitrogen pollution to the Bay comes from agriculture.

  • 25% of the nitrogen pollution comes from fertilizer

  • 33% of the nitrogen pollution comes from air pollution

  • Nitrogen pollution from manure and fertilizer is washed into the Bay (more on this in the next activity)

  • Nitrogen pollution from sewage and industry comes from sewage that is dumped into tributaries or into the Bay directly. It also comes partly from people dumping into the Bay.


Ask students if they were right in their guess about where the nitrogen pollution is coming from. Then ask them how they think pollution in the air gets into the Bay. Again, don’t tell them if they are right or wrong, just acknowledge their guesses. The point of this question is to get their minds thinking about how air pollution could possibly get into the water.

Step 4

4. Return to the Clue Board

Go back to the clue board and see if there are any more clues to add. For example, you might add:

  • Nitrogen and phosphorus pollution are causing the algae bloom

  • Most nitrogen pollution comes from agriculture


Tell students that they now have a good idea what is causing the fish to die, but if they want to stop the problem, they need to go to the source of it.

5. Formative Assessment

Have students complete the “Conclusion” prompt on the back of their sheet: Do you think most of the pollution in the Bay comes from people dumping it into the water on purpose? Use information from the infographic to support your answer.

  • Answer: No, most of the nitrogen pollution to the Bay is unintentional. It is from pollution from the land and the air that ends up in the Bay accidentally. Only a small portion of the pollution in the Bay is dumped there intentionally.

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