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Chesapeake Bay

Activity 9 (Explain): Modeling Pollution in the

Chesapeake Bay

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Activity Overview

Activity Summary

In this activity, students begin the challenging task of developing a model showing how pollution gets into the Chesapeake Bay. They work collaboratively to come up with a list of what belongs in the model, and then they assemble the model together as a class.

A Note About Timing for This Activity: The Chesapeake Bay pollution model can get rather complex. As such, you may want to build it slowly throughout the course of the module as opposed to waiting until this point. Either way, students will need support building the model, so be sure to consider ways to scaffold the model-building however you choose to implement it.

Activity Objectives & Materials

Approximate Time: 45 minutes​


  • Students will begin to create a model of how pollution enters the Chesapeake Bay



  • Computer & projector

  • Pre-printed/written parts of the Chesapeake Bay pollution model (these can be on paper or on sentence strips) including lots of arrows

  • Extra paper and markers to add components to the model


  • None

Standards Connection

DCI: LS2.C: Ecosystem Dynamics, Functioning, and Resilience

DCI: ESS3.C: Human Impacts on Earth Systems

SEP: Creating & Using Models

CCC: Cause & Effect, Systems and System Models



Name three ways that nitrogen pollution can get into the Chesapeake Bay.

  • Lots of answers are possible: air pollution drifts into the watershed and falls into the water; air pollution falls on the land in the watershed and get washed into the Bay, fertilizer runs off farms into the Bay, etc.


1. Frame the Activity

Refresh students’ memory of how far they’ve come in investigating what killed the fish in the Chesapeake Bay by reviewing the clues board. They know that the fish died from a lack of dissolved oxygen. They know that this was caused by an algae bloom which was caused by excess nutrients in the Bay. They know that those nutrients came primarily from agriculture and from air pollution. In order to see how all these pieces fit together, marine biologists like themselves would build a model of how pollution gets into the Bay.


Tell students that modeling is a very important part of the scientific process, especially for scientists who study ecology and ecosystems like the Chesapeake Bay. Today they’re going to learn about models and they will create a model together of how pollution affects the Chesapeake Bay. Their model will help them to figure out how to protect the fish and the water.

Step 1

2. Food Webs as a Model

Display a food web diagram that all students can see, such as the one below. Ask if they have seen anything like this before and what it is. Students may or may not be familiar with food webs, so adjust the time you spend reviewing the food web to make sure all students understand what it shows. Tell students that food webs are one kind of model of an ecosystem. Ask students what they see in the model (arrows, names/pictures of animals, etc.). Tell students that in a food web model, the arrows show how energy moves through an ecosystem. Plants get their energy from the sun so they are at the base of the food web. The arrows show the energy going from the plants, to the animals that eat the plants, and then to animals that eat those animals.

Chesapeake Bay Food Web.jpg

Teacher Tip: The goal of introducing the food web model is not to teach food webs, it is to help students recognize the parts of a model using something that they may already be familiar with. Don’t get too hung up on teaching the food web.

3. Introducing the Components of the CB pollution model

Tell students that the model they are building will show how pollution gets into the Bay and affects the living things there. Ask students what things belong in a Chesapeake Bay pollution model. Encourage them to look through their notes from previous activities and at the word wall in the classroom. Possible student responses:

  • The Chesapeake Bay water, dead fish, polluted rain, air pollution, the watershed, the airshed, fertilizer, algae, and wet/dry deposition.


As students name different things for the model, take out the preprinted sentence strip with each concept/object on it from your pre-printed materials and show it to students. If students name something that you have not premade, write it on a sentence strip or piece of paper and show it to students. Continue adding new components to the model until students’ ideas are exhausted. If there are pieces missing, do not worry about introducing them. Students will likely recognize the missing pieces as they are building the model.

Modification: Building the model will likely require a lot of hands-on attention from the teacher, but if you have a large class or you think students will be able to work more independently, consider breaking the class into two or more groups. This has the added benefit of allowing students to see a different version of the model.

Step 4

4. Building the Model

Give one component of the model or arrow to each of the students in the class (depending on the number of students, you may want to have duplicates of some, or you may want to have students work with a partner). Save the dead fish for yourself. Tell students that this investigation started with the dead fish, so you’re going to start the model with the dead fish in the Bay. Put the fish in the middle of the space. Tell students that you are going to work backwards from the dead fish all the way back to the air pollution. Ask who has something that connects to the dead fish (dead algae, no oxygen, algae bloom are all good places to start). Have these students add their concepts to the model, using arrows to show how one thing connects to another. Continue building this way, moving backwards. If you hit a point where it makes sense to go in a different direction, then do so. If students have questions or want to move an arrow or an object, that’s fine, but have students talk to one another about it (ex. “I think this arrow should go here. Is it okay if I move it?”). If students recognize that something is missing, have additional paper on hand so they can add it to the model.


A sample model students might come up with could look like this:

Chesapeake Bay Pollution Model 1.jpg

Keep in mind that there is no “perfect” model, but the model should be accurate and make sense.

Teacher Tips: Building the model works best if you can find a large open space in your classroom, or make a space on the floor where all students can see. You can also use a bulletin board and put up the model using push pins. If these types of spaces are not available, consider finding a space to use for the day like the cafeteria (when it is vacant), an outdoor space, or a stage in a school auditorium.

Building a complex model like this is bound to be a challenge for middle school students. The key is to go step by step and make little improvements along the way. Use questions to help students make improvements and recognize missing components. Most importantly, let students do the hard work of figuring the model out themselves.

5. Reviewing the Model

Once the model is finished (for now), take time to review parts of the model with students to check for understanding and clear up misconceptions. You may want to attach the model to butcher paper so it can be moved (you can also write additional labels on the butcher paper). Make sure to put the model up in a prominent place for students to use for the remainder of the module. It will be useful to reference the model, and add to or modify it if necessary.

6. Formative Assessment

Have students reflect on the process of making the model. Here are some sample questions to consider:

  • What did you like about building the model?

  • What was the most challenge part about building the model?

  • If you built another model like this, what would you do differently?

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