Bioaccumulation of Toxins

Students will use marshmallows to simulate toxins in the environment. Concentrations of these toxins will be modeled and calculated as they bioaccumulate up the food chain. Methylmercury and POPs are substances that bioaccumulate in the Arctic food chain. OASIS scientists studied these in Barrow, Alaska. (See Ocean Atmosphere Sea Ice and Snow (OASIS) Project at www.polartrec.com)

Objective

After completing this lesson students will be able to:

• Define toxin
• Understand the terms dosage and duration in relation to toxicity
• Model and calculate bioaccumulation of toxins throughout a food chain

Preparation

1. Print out a student worksheet and student diagram for each student.

2. Print out a set of 10 phytoplankton cards for each group of student. (Use the option for printing 9 wallet size pictures per sheet.) Cut out and place 10 cards in a Ziploc bag for each group of students.

3. Count out 110 marshmallows (10 extra) into a Ziploc bag for each group of students.

Procedure

1. Students will read through the "Background" section of the assignment and write down in their notebooks definitions for: a. Bioaccumulation b. Toxin c. Ingestion d. Dosage e. Duration f. Methylmercury g. POPs

2. Discuss the definitions with the students after they finish reading and recording them.

3. Break the students up into groups of 2-3 and hand each of them a set of phytoplankton cards and marshmallows.

4. Point out that the marshmallows are going to represent a toxin concentration of "1".

5. Explain the "Bioaccumulation in the Food Chain" diagram to the students. a. Point out that in this simplified version of a food chain that phytoplankton is at the bottom and birds and mammals are at the top of the food chain. b. As you move up the food chain the toxin concentration increases in each organism. c. On the "Concentration of Toxins" chart, students will record the calculated concentrations from the lesson.

6. If you have a SMARTboard available, you can show these two charts in the "Bioaccumulation_Lesson.notebook file. a. On page 3 of this file is an interactive lesson where the students can touch each picture in the diagram to flip it over and reveal the concentration of toxin.

7. Work as a whole group with the students to answer questions #1 and #2 on the worksheet and on the "Concentration of Toxins" Chart.

8. Have the students work with their partners on questions #4 and #5.

9. Students may come up to the SMARTboard and check their answers for the concentrations of toxins.

10. You can help the students with the math in question #6 as needed. Show them a one-pound bag of marshmallows so that they can get an understanding of the quantity of toxins being discussed.

11. When the students get to questions #9 and #10 you can start a classroom discussion to help them answer the questions. See answer key.

Extension

The concepts in this lesson can be continued in the "Bioaccumulation WebQuest" Lesson (also available through the PolarTREC Learning Resources). Students will research bioaccumulation of toxins in their life and in the Arctic.

Assessment

Students will be graded on correct answers according to the answer sheet. I have assigned 3 points for each question that is answered correctly in a complete sentence. The toxin concentration chart receives a total of 10 points. Each line of boxes for the individual organisms is worth 2 points each.

Credits

Betsy Wilkening, ewilkening [at] amphi.com The images of phytoplankton and organisms are copyright free from US National Oceanic and Atmospheric Administration. The clip art images are copyright free from SMART Notebook.