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Stage 1
Identify Desired Results

Catchy Title: Something Fishy
Theme/Topic of Lesson: Bioaccumulation of Mercury
Time Commitment: 3-4 45minute periods
Subject Area(s):
    Science - Environmental
    Science - Ecology
Grade Level(s): 6,7,8,9,10,11,12
Standards Alignment:
Class Challenge Question:

Why do we have to worry about the health effects of very small amounts of mercury in waters from which we eat fish?


In this lesson students will explore the dangers of eating high levels of mercury and learn how small amounts of mercury in water accumulate in greater quantities in organisms higher in the food chain.

The lesson begins with the students using an online mercury calculator to calculate how much mercury is in their diet. They will then learn why knowing this information is important and what the health effects of high levels of mercury are. Next the students will investigate how mercury gets into the food chain, and finally how it accumulates in the food chain. The concept of food chains and webs are reviewed and the processes of  bioaccumulation and biomagnification introduced. The lesson then returns to the health effects for a tertiary consumers, which we humans often are.

Please note: There are alternate presentation methods described for this lesson. Choose what will work best for your students.

Stage 2
Determine Acceptable Evidence

Life Science
Maryland Content Standards
Students will use scientific skills and processes to explain the dynamic nature of living things, their interactions, and the results from the interactions that occur over time.
Maryland State Indicators
analyze the interdependence of diverse living organisms and their interactions with the components of the biosphere. The student will analyze the interrelationships and interdependencies among different organisms and explain how these relationships contribute to the stability of the ecosystem (diversity, succession, niche). (CLG 3.5.2.) The student will investigate how natural and man-made changes in environmental conditions will affect individual organisms and the dynamics of populations (depletion of food, destruction of habitats, disease, natural disasters, pollution, population increase, urbanization). (CLG 3.5.3.) The student will illustrate how all organisms are part of and depend on two major global food webs (oceanic food web, terrestrial food web). (CLG 3.5.4.) The student will analyze the consequences and/or trade-offs between technological changes and their effect on the individual, society and the environment. They may select topics such as bioethics, genetic engineering, endangered species, and food supply. (CLG 3.6.1.)
Environmental Science
Maryland Content Standards
Students will use scientific skills and processes to explain the interactions of environmental factors (living and non-living) and analyze their impact from a local to a global perspective.
Maryland State Indicators
use physical, chemical, biological, and ecological concepts to analyze and explain the interdependence of organisms within the environment. The student will explain how organisms are linked by the transfer and transformation of matter and energy at the ecosystem level. (CLG 6.2.1.) The student will explain why interrelationships & interdependencies of organisms contribute to the dynamics of ecosystems. (CLG 6.2.2.) The student will conclude that populations grow or decline due to a variety of factors.(CLG 6.2.3.) The student will provide examples showing that natural selection leads to organisms that are well suited for survival in particular environments. (CLG 6.2.4.)
Environmental Science
Maryland Content Standards
Students will use scientific skills and processes to explain the interactions of environmental factors (living and non-living) and analyze their impact from a local to a global perspective.
Maryland State Indicators
use concepts from chemistry, physics, biology, and ecology to analyze and interpret the impact both positive (recycling) and negative (toxic wastes) of human activities on the earth's resources (land, water, air, energy, biological). The student will evaluate the interrelationships between humans and air quality. (CLG 6.3.1.) The student will evaluate the interrelationship between humans and water quality and quantity.(CLG 6.3.2.) The student will evaluate the interrelationships between humans and land resources. (CLG 6.3.3.) The student will evaluate the interrelationships between humans and biological resources. (CLG 6.3.4.) The student will evaluate the interrelationships between humans and energy resources. (CLG 6.3.5.)

Learning Objectives:

The Students will:
  • calculate their own mercury consumption and determine if they should reduce their intake of high mercury foods

  • list the health of effects of high levels of mercury on humans.

  • explain how mercury enters the food chain

  • define and give an example of a food chain, identify each level and explain the energy loss that occurs at each level

  • define biomagnification and demonstrate how it occurs by calculating the relative amounts of mercury at different levels of a food chain.


Students assume the role of a nutritionist. They will be given a client with a diet which includes fish. They will have to determine whether the diet has safe levels of mercury, and if not, how to adjust it to fit the FDA guidelines. Additionally, they will have to trace any mercury in the diet back through the food chain, explaining how it accumulated and where it could have come from. They will also have to explain to the client why it is dangerous to consume high levels of mercury (see ASSESSMENT).

An alternative assessment is at the end of DAY 3 WORKSHEET . After applying what they learned about bioaccumulation to other situations,  students are asked to compose an email (or letter) explaining why using pesticides in a garden may be dangerous to birds or other organisms.

These assessment will probably have to be modified for  High School students.

Stage 3
Plan Learning Experiences


Internet SitesNRDC mercury calculator

Input what fish you have eaten and this site will tell you how much mercury you have consumed. There are other mercury calculators on the web, but this is the easiest to use.
Is Mercury the Achilles Heel of the Restoration Effort?

 This web page is part of the USGS website and deals with restoration in South Florida. It has a great diagram of how mercury enters the water, and one of bioaccumulation of mercury in the food chain.
Energy Transfer

This is a water filled activity which helps demonstrate loss of energy as you go up a food chain
Mercury in Fish

This is an article from the office of Environmental Health Hazard Assessment in California. It has information about the sources and effects of mercury
ToxFAQs for Mercury

This is a fact sheet about mercury from the Agency for Toxic Substances and Disease Registry (ASTDR). It briefly reviews sources of mercury and discusses the health effects in more depth.
Mercury Contamination in Fish--Know Where it's Coming From

This portion of the NRDC website discusses sources of mercury pollution in the water.
Mercury Contamination in Fish--Learn about Mercury and its Effects

This portion of the NRDC website discusses the health effects of mercury.
Project Flow: Who's Eating Whom?

This is Lesson 2 from Project Flow, a project of SeaGrant Michigan. The lesson and associated activity teach about energy flow in food chains. The cards describing the different organisms are the basis for the Great Lakes food web attached to this activity.
Food Chains

This web site is an excellent resource. It not only contains the basics of food chains and food webs, but information about the transfer of energy and biomass in living systems, in some detail. From Kimball's Biology Pages.
Food Chains and Webs

This site is also a good source of background and general information. It also contains a link to some good information about bioaccumulation and biomagnification. Click on Food Chains and Webs. From Marietta College Biology.
Bioaccumulation and Biomagnification

A page from Marietta College Biology that explains bioaccumulation and biomagnification and gives some concrete examples.
It's all interconnected

This lesson plan from the raptor center teaches about food webs and more. Scroll down to #5 and #6 for the most relevant parts.
Study Questions Low Level Effect of Mercury

An article about questions arising about the effects of mercury. Examines different studies and the issue of saltwater vs. freshwater fish.
Why Mercury Levels in Water Don't Equal Levels in Fish

Impact of the amount of algae on the biomagnification of mercury.
Commercial Fish: Eat up Despite Low Levels of Mercury

Discusses a study done in the Republic of Seychelles where people consume large amounts of fish, with mercury levels similar to those sold in the U.S. and have not shown adverse affects
Sources and Variations of Mercury in Tuna

Potential differences in mercury methylation in fresh and ocean waters.

Per class

    Large open space that can get wet



    large relatively open space


    red, blue, green and brown construction paper

    feeding cards printed out from lesson

  • Something Fishy-- Answers for MERCURY HEALTH EFFECTS  (View)
  • Something Fishy--Answers for MERCURY SOURCES  (View)
  • Something Fishy--Mercury Diagram  (View)
  • Something Fishy--Example for Energy Pyramid-Mercury Ladder  (View)

    plain and colored pasta (about 1 lb. of each/20 students)

  • Something Fishy-- Day 1 Power Point Slides  (View)
  • Something Fishy--Day 2 Teacher Resource-Deadly Links Game  (View)
  • Something Fishy--Math Follow Up  (View)
  • Something Fishy--Middle School Standards  (View)
as determined by instructor
  • Computer with internet access. If there is only one computer for the class there should be a projector.

  • calculators, if desired

  • Something Fishy-- MERCURY HEALTH EFFECTS  (View)
  • Something Fishy-- MERCURY SOURCES  (View)
  • Something Fishy--Food Web  (View)
  • Something Fishy--Energy PyramidMercury Ladder  (View)
  • Something Fishy--Biomagnification diagram  (View)
  • Something Fishy--One Part per Trillion  (View)
Per student team/group of 4
  • 2 five gallon buckets or other large containers to hold water and graduated cylinder or other way of measuring water (Energy Transfer)

Per Student
  • signs and string to hang signs around students' necks (Deadly Links and Energy Transfer)

  • envelope (Project Flow)

  • Something Fishy--Assessment  (View)
  • paper lunch bag (Deadly Links)
  • Large (20 oz) cup (Energy Transfer)
  • Something Fishy--Mercury Menu  (View)
  • Something Fishy- Sources and Effects Organizer  (View)
  • Something Fishy-Consolidated Reading  (View)
  • Something Fishy--Day 1 Worksheet  (View)
  • Something Fishy-Day 2 Worksheet  (View)
  • Something Fishy-Day 3 Worksheet  (View)

  • bioaccumulation - increase in concentration of a pollutant from the environment to the first link in a food chain
  • biomagnification - increase in concentration of a pollutant from one link in a food chain to another
  • consumer - biologically--a heterotroph--an organism that eats other living organisms (plants or animals)
  • food chain - a pathway energy and nutrients follow in an ecosystem
  • food web - a network of the many possible food chains in an ecosystem
  • producer - biologically--an autotroph--an organism which makes its own food from inorganic substances (carbon dioxide and water with solar energy in the case of plants)


This lesson begins by asking students to calculate concentration of mercury in their blood using the online mercury calculator. This should lead into a discussion of why is there an unsafe amount of mercury--what does it do? where does it come from? how come fish have high levels of mercury?

Students will then investigate the effects of mercury on human health and find out where the mercury originates.

Finally, students will investigate how small amounts of mercury accumulate to become relatively highly concentrated in fish. Ideally, the class should have already learned about food chains and webs. They will also hopefully know about producers and various levels of consumers. This information should be reviewed. In addition, energy loss at each level of the pyramid should be reviewed or taught.. How mercury enters water and the aquatic food web will be reviewed from the first part of the lesson. . The fact that it is fat soluable and therefore stays in the tissues of the organism that ingests them means none (or little) of the mercury is lost as it rises in the food chain. Thus it accumulates, eventually to toxic levels. Students will calculate the levels of the pollutants that will result at various stages of an aquatic food chain.

Students will conclude by returning to their original mercury menus. They will relate the food chains they have studied to the fish on the menu and will try to find a diet that contains fish and safe levels of mercury.  The class can attempt to answer real life questions such as: What are safe levels of fish (and pollutants) for humans to consume? What does the concentration of the pollutants in the water have to be in order for the fish to be safe for human consumption?

Alternatively, students will conclude by extrapolating what they learned about mercury and bioaccumulation to other substances and environments (see DAY 3 WORKSHEET)

First one or two days: Calculate
Daily Challenge Question: How much mercury do you eat? Why is it not safe to eat high levels of mercury? Where does the mercury in food come from?
1-2 45 minute periods
Set-up Directions:

Ideally, each student or group of students will have a computer with internet access. If not, this exercise can be done in groups with numbers given by each group to be used in the  mercury calculator as a class.

Each student or group will have one each of MERCURY HEALTH EFFECTS ORGANIZER and MERCURY SOURCES ORGANIZER or they can use SOURCES AND EFFECTS ORGANIZER which consolidates both into one worksheet.

You may choose to give each student or group a MERCURY MENU (see activity 1: How Much Mercury?) or they can use DAY 1 WORKSHEET,  or both.

You can also use DAY 1 POWERPOINT SLIDES and/or print out as an overhead, use a projector, have the students view on line or hand out the sample MERCURY DIAGRAM.

Teacher Presentation & Motivation:

Each Activity described for day one could potentially take an entire 45 minute class period, so this "day" may actually take 2 days or one 90 minute period.

The teacher should be familiar with how to use the mercury calculator. In addition, the websites to investigate health effects and sources of mercury should be reviewed. They contain variations on the same information and familiarity with their contents would be helpful. It would be very useful to bookmark the sites to be used in advance.

Students should be told to use the Mercury Calculator without any introduction. This will hopefully lead them to wonder: Why do I care if I have high levels of mercury? Why is there mercury in the water? Why do small amounts of mercury in water end up being large amounts of mercury in fish? Encourage students to ask these questions and try to brainstorm answers as a class.

Once they have asked the questions, you will let them find the answers to the first two of those questions from the internet during this class period. They will use the internet materials to determine what the effects of mercury are on humans. They will also find out what the sources of mercury pollution are. A brief review of the water cycle is necessary here, as much mercury enters the water from the air.

Activity 1 - How Much Mercury?

Have students write down all the fish they have eaten in the past month. Give the students  the direct link to the mercury calculator. The direct link is advantageous, because at this point you do not want them to be able to go anywhere else in the site. Initially the calculator asks for their weight. If this will be a problem, assign 2 or 3 demonstration weights to use. Let the students input their fish consumption and find out  and record the mercury level in their blood (or in blood of people weighing demo weight) Using the same menu, have students investigate the effects of body weight on mercury. Record mercury levels for different body weights. They should notice that the more someone weighs the more mercury they can tolerate. Discuss the implications of this for children.  DAY 1 WORKSHEET can be used to structure this activity.  Use the MERCURY MENU for students who need more guidance or don't eat fish. The MERCURY MENU is 2 pages with the same layout, but different fish menus.

If there is only one computer for the class, divide the class into four or five groups. Give the list of fish to each group and have them make up a representative menu. Use the calculator for the menu of each group.

Hopefully, this exercise will generate many questions. Basically you will want your students to wonder: Why do I care if I have high levels of mercury? Why is there mercury in the water? Why do small amounts of mercury in water end up being large amounts of mercury in fish?

Focus for Media Interaction
Focus for Media Interaction: The focus for media interaction is a specific task to complete and/or information to identify during or after viewing of video segments, Web sites or other multimedia elements.

Students will calculate mercury level in their blood using the mercury calculator.

Viewing Activities
What will your students be responsible for while viewing this piece of multi-media or video?

They will record the "menu" they have chosen and the levels of mercury resulting for at least 2 different body weights.

Post Viewing Activities
How will students utilize the information they gathered while viewing the multi-media or video?

Students will determine if the levels of mercury they consume are safe.

Activity 2 - What's the Harm? and What's the Source?

Students will use the assigned internet sites to determine the health effects of high levels of mercury in humans.  They will investigate what the sources of mercury in water are. They will complete a graphic organizer for each--MERCURY HEALTH EFFECTS and MERCURY SOURCES.(These can be filled out as hard copies or online) or SOURCES AND EFFECTS ORGANIZER which consolidates both into one sheet.

There are three internet sites listed below that provide information about these topics. Each group can be assigned one site from which to gather information, and when all are finished they can compare the information they have found. Alternatively, the groups can be sent to all three sites and can pick the information to include in the organizers.  The information from the sites can be printed out if there is not a computer for each group. For greater efficiency, have students read the CONSOLIDATED READING.

State of California OEHHA Mercury in Fish article has information on both sources and health effects

ATSDR ToxFAQs for Mercury: Briefly covers sources of mercury, covers health issues more in depth. 

The NRDC website has information on sources of mercury pollution (first link) and on health effects of mercury (second link)

Other sources are listed in the Resource section of this lesson.

Focus for Media Interaction
Focus for Media Interaction: The focus for media interaction is a specific task to complete and/or information to identify during or after viewing of video segments, Web sites or other multimedia elements.

Students will find out the health effects of mercury on humans and the sources of mercury in water.

Viewing Activities
What will your students be responsible for while viewing this piece of multi-media or video?

Students will fill out a graphic organizer detailing health effects of mercury in humans including effects on fetuses/infants, children, adults with moderate exposures, and adults with extremely high exposure. They will also fill out an organizer with sources of mercury in water, including natural sources, sources from air, sources entering directly to water, and uses of mercury. These organizers can be printed out and filled in or filled in online.

Post Viewing Activities
How will students utilize the information they gathered while viewing the multi-media or video?

Students will share findings with the class  Compare and contrast information from the three different websites. Discuss why the information is not identical. (For health effects, possibly each website is looking at effects of different levels of exposure; students should also consider the website source.) For sources of mercury concentrate on air pollution as a source of mercury . Students should be able to explain how mercury enters the water from the air and that this is particularly difficult to control.

Have additional copies of the organizers available if using hard copies so that each student can make a comprehensive, correct copy at the end of the activity.

Wrap Up:

Review the information about high levels of mercury and what the potential health effects are. Have students share what they found out about sources of mercury pollution, and how much mercury is in the water.  Show the second PowerPoint slide from DAY 1 POWERPOINT showing the mercury chain MERCURY DIAGRAM (linked to the lesson)from the South  Florida Information Access website which reviews sources and movement of mercury. (Show only the top, the bottom can be discussed the next day.) 

Tell students that there are may only be 10 ppt (10 parts per trillion) of mercury in the water. Lead them to realize how small this amount is--and ask if they think it is dangerous. (A part per trillion is a pinch of salt on 10,000 toms of potato chips, or a  6" leap in the journey to the sun...see these and others at, or see the same information on the ONE PART PER TRILLION handout.  

Return to the calculator and note the amounts of mercury in some fish (tuna fish is a great example). Have students to try to figure out how such small amounts become so large--tell them that is what you will be discussing the following day. The analysis questions from the DAY1 POWERPOINT can be used for review.(What are the sources of mercury? Why is eating too much fish a problem? How can you still eat fish and avoid mercury poisoning?) There is also a homework question as part of the PowerPoint ( As you learned in your investigation today, some fish have higher concentrations of mercury in their bodies than in others. For example, if you eat a large serving of tuna fish, you are consuming almost 10 times more mercury than you would if you were to eat the same amount of anchovies. Both types of fish live in the same environment. Make a prediction as to why some fish have more mercury in their bodies than others.)  The last PowerPoint slide is a Drill for the next day.

2nd day: Food Web
Daily Challenge Question: How does a little mercury become a lot in the fish we eat?
1 45minute period
Set-up Directions:


Each student of group should have a copy of the  FOOD WEB, and some of the blank ENERGY PYRAMIDS/MERCURY LADDER or they can use DAY 2 WORKSHEET.

You can also print out as an overhead, use a projector, have the students view on line or hand out the sample BIOMAGNIFICATION DIAGRAM.

There are some optional activities depending on the time, space,previous knowledge of students, curriculum, etc.:

For Energy Transfer per group: 

This activity requires an outdoor space that can get wet.

Signs (index cards or larger) and string to hang signs on each student
Two five gallon buckets (or other large containers for water)
Large cups(20 oz size)--at least one per student   

Graduated cylinder or other measuring device to measure final water volume.

 For Project Flow--Lesson 2:Who's Eating Whom? :

A relatively large, open room, or outdoor space

construction paper: red, blue, brown and green to make tokens

one envelope/student

Copy of feeding behavior cards (provided with lesson)

For Deadly Links (see DAY 2 TEACHER RESOURCE DEADLY LINKS sheet)

1 pound each of plain and colored pasta/ 20 students.

signs and string to hang signs around students' necks

1 paper lunch bag/student

Teacher Presentation & Motivation:

Review the MERCURY DIAGRAM from the end of the lesson on the first  and ask if anyone figured out how so little mercury could become so much. Show the students the bottom of the diagram (2nd page if using hard copy) with the food chain. Alternatively, use the Drill Day 2 from the DAY1 POWERPOINT PRESENTATION as an introduction.

Review the concept of a food chain or web, or  introduce it if it has not been previously taught. There are resources listed to help teach food chains and energy transfers. Directions for the Deadly Links game are given in DAY 2 TEACHER RESOURCE DEADLY LINKS GAME sheet.There are two other active games for teaching energy transfer from the internet cited . Energy transfer is a confusing concept, so it is a good idea to do one of the activities if you have the time and resources. They are also fun! 
Whether or not a game is played, energy calculations should be done. The food web diagram provided is based on the feeding cards provided with the Project Flow lesson. Even if the activity isn't used, the information is useful for making food chains to do the energy calculations.

Once the students  understand the transfer of energy, return to the concept of mercury. How come mercury accumulates if energy is lost? See if the students can come up with the answer from the web sites they visited yesterday, or reading the side of the introductory food chain they saw today. The  important fact to know is that mercury, unlike energy, is stored for a long period of time in the fat cells of the body and so it accumulates. In addition, because energy is lost at each level, the higher you climb on the food chain/energy pyramid, the more organisms in total you are consuming, and therefore the more mercury you are consuming.

The numbers used in these activities were chosen for simplicity. The loss of energy at each level of the food chain is estimated to be 90% for the purposes of this activity. Slightly more accurate numbers are 17% of energy is transferred from producers to consumers, and 4.5% is transferred from  primary consumer to secondary consumer (these can be rounded to 20% and 5%) In any case it is all an estimate and the numbers are important in that they illustrate the concept. The activity can assume more mathematical sophistication depending on the level of the students and/or if done in conjunction with a math class. Some math extensions in conjunction with the Deadly Links game are explained on MATH FOLLOW UP sheet.  In depth analysis of the data from the games or of the movement of toxins up the food chain are essential to students' understanding of bioaccumulation

Activity 1 - Food Chains

Basic knowledge of food chains and food webs is assumed in the remainder of the lesson. If you are teaching this material at this point, below are two resources which have good explanations.

The Food Chain Page is an excellent resource. It not only contains the basics of food chains and food webs, but information about the transfer of energy and biomass in living systems, in some detail.

Food Chains and Webs is also a good source of background and general information. It also contains a link to some good information about bioaccumulation and biomagnification. 

Introduce or review the concept of an energy pyramid and the loss of energy at each level of a food chain. Use WORKSHEET DAY 2 to review food chains and introduce the Deadly Links game.

Alternatively, begin with a simple food chain. One example is:
Algae ------>Insect------> Crayfish--------> Heron
Make sure that students know that algae is the plant and so is the producer, the insect is the primary (first order) consumer that eats plants, the crayfish is the secondary (second order) consumer that eats plant eaters, and the heron the tertiary (third order) consumer that eats animals that eat other animals.
Explain that only 10% (or whichever number you choose to use) of the energy in an organism is conserved as you go up the food chain, so in order to gain enough energy ( assume all organisms need a random number (1000, or 10000 are convenient) units of energy to survive for a time period) the heron has to eat many crayfish and so there must be a number of crayfish eating quite a few insects and many insects eating many plants. Show the energy pyramid.
Have the students answer the following questions as a class.
1. According to the pyramid, what is the ratio of the energy available to the tertiary consumer to the energy available from the producers? (1/1000)
2. If 100 insects eat 1000 algae plants, how many crayfish can they provide with energy? (10)
3. What happens to the pyramid if there are 10 insects eating 100 algae plants? (there is only one crayfish, and so not enough energy for the heron)
4. If there are 5000 insects how many algae plants are necessary to provide them with energy? (50,000) How many crayfish can they support? (500) How many herons can those crayfish support? (50)

(adapted from: It's all Interconnected

You can have students make up more questions, or you can make up more questions as needed.

If you are planning to play the Deadly Links game or either of the other games this is the appropriate time to do it.

Show the students or hand out the FOOD WEB and give each student the ENERGY PYRAMID-MERCURY LADDER worksheet. As a class find food chains within the food web. Note that the food chains can be different lengths.
Have each student or group choose a food chain and fill in the energy pyramid beginning at the top with one of that organism at the highest level.(see EXAMPLE of ENERGY PYRAMID /MERCURY LADDER) Not all levels will be necessarily be  filled in?the more levels there are, the more producers will be necessary to support that pyramid.. Review the numbers in the pyramid with the class. Remind the students that these numbers are examples!!!

See MATH FOLLOW UP sheet for ideas to use in math class in conjunction with the Deadly Links game.

Activity 2 - Bioaccumulation and BioMagnification

Using the same food chain they used in activity one, have students imagine that mercury has entered the water. This is a good opportunity to review the first part of the lesson and ask what are the possible ways that mercury can enter the water supply. Let students look at their organizers if necessary.
Mercury is now in the water in concentrations of 1ppt. Review what a ppt is and have students give you some examples.
Have the students imagine the plants in the water are exposed to this mercury. (For an example, imagine that this concentration of mercury is introduced each time it rains…)
The plants take in the mercury with the water they use, and it is stored in their tissues, primarily in fat tissue. Very little is released once it is in the tissue and so the plant can accumulate quite a large amount of mercury—this is called BIOACCUMULATION.
(see "Bioaccumulation and Biomagnification" for more information)
At the bottom of the mercury ladder, have the students write plants. Estimate that the plants have accumulated 250 ppt of mercury. Have the students fill in the ladder with the amounts of mercury assuming each organism needs a set amount of energy (like the previous activity, 1000 or 10,000 units are easy numbers to use)It should become apparent that the higher up on the food chain you are, the more mercury you accumulate.
The same organism may contain different amounts of mercury if they are on different levels of two different food chains. This is why the estimates of mercury in any one organism is an average of possibilities and an estimate. 
Show the BIOMAGNIFICATION DIAGRAM. Point out to students that the predicted numbers for total PCB (another pollutant stored in fats) accumulation in a tertiary consumer in the Great Lakes are predicted to be about 10x the numbers arrived at in our exercise.
This phenomenon of increasing concentration as you proceed up the food chain is called BIOMAGNIFICATION.

Wrap Up:

Review with students the difference between how energy and how mercury travel up a food chain. What makes mercury and other similar toxins so dangerous is that they accumulate and then magnify as they go up the rungs of the food chain.
Tell students that the next activity involves seeing the connection between the food chains they have just studied and the mercury menus in the previous lesson. If there is time, see if they can make the connection.

3rd Day: Mercury in the Food Chain
Daily Challenge Question: How do you evaluate the level of mercury in your diet?
1 45 minute period
Set-up Directions:

Set Up:
Computers with internet access and the mercury calculator website.
Original MERCURY MENUs (that they recorded or were distributed on the first day) 
Calculators may be useful
Students should have their ORGANIZERS from Day 1

Teacher Presentation & Motivation:

This is the final day for this lesson and should bring together all the different concepts which have been taught. Students already know most of the information and this is a chance to review and put it together as a whole. There are a number of calculations described in these activities. They can be eliminated and the implications discussed, they can be done as a class, or students can do them and additional ones independently.

In activity 2 students will modify their mercury menus so they are safe. This activity can serve as a focus for the review and activity 1 eliminated or abbreviated if desired.

Alternatively, students can complete DAY 3 WORKSHEET, reviewing food chains and bioaccumulation and expanding the discussion of bioaccumulation and the health risks it poses beyond mercury. The analysis question at the end of the worksheet can be used as an assessment.

If time and student ability allows, students can be made aware that not everyone agrees on the effects of mercury and there seem to be  differences between ocean and freshwater fish. There are also some that believe that the benefits of eating fish outweigh the dangers of mercury. Some websites with this information are listed in the resources section of this lesson. These issues can be discussed and debated.

Activity 1 - Tracing Mercury Back

Have students return to the mercury menus given out on the first day.
Review with them:
What the effects of mercury may be
What the sources of mercury may be
How the mercury gets into the fish we eat

Have students brainstorm reasons some fish are lower in mercury than others (they are lower on the food chain, have less fatty tissue, live in waters which are unpolluted by mercury).

Have the students look up the concentrations of mercury in a type of fish?chunk light tuna is a good example. Relate what you calculated in Activity 2 to the amounts that are listed in the calculator.
In 1 portion of 3 oz of chunk light tuna there is 0.33ug /L of mercury in blood

For example say you have 5L of blood
So there is a total of 1.65ug (.33ug/L x 5L) of mercury in 3 oz of this tuna.
Say a tuna is 70 pounds, there are about 350 servings in one tuna. (70 pounds= 1120 oz 1120/3=373) which means the tuna has 577.5 ug of mercury total in the tuna. (this is inaccurate because there is white and light in one tuna,?but it is used as an example)

Have the students trace this amount of mercury back through a food chain using these numbers. (the food chain can be phytoplankton-->zooplankton-->mullet-->tuna) and try to calculate the amounts of mercury in the water. What would happen if we changed the tuna to half "white" tuna? all "white" tuna?

The EPA has set the safe level of mercury in blood at 5.8ug/L. Have students trace this amount back through the food chain in a similar way, and figure out approximately what is considered a ?safe? level of mercury in the water.
(Using 6ug/L you can have 30 ug in 5L of blood, if this is 1/40th of a whole fish the total mercury in the fish is 120 ug?etc.)

Activity 2 - Modifying the Mercury Menu

Using the mercury calculator, have students modify their original mercury menus so that they are safe, but they are still eating fish. Look at numbers of portions, sizes of portions, and different types of fish. Note also that the size of a person is also important—the larger the person, the more blood, the greater the total amount of mercury that person can handle.

Focus for Media Interaction
Focus for Media Interaction: The focus for media interaction is a specific task to complete and/or information to identify during or after viewing of video segments, Web sites or other multimedia elements.

Students must experiment until they find a menu that has safe levels of mercury.

Viewing Activities
What will your students be responsible for while viewing this piece of multi-media or video?

The students will write the menu down and note how much mercury it contains.

Post Viewing Activities
How will students utilize the information they gathered while viewing the multi-media or video?

Students should realize that they can eat fish and still have safe levels of mercury.

Wrap Up:

Review the revised mercury menus, and incorporate discussion about the sources of mercury pollution, the effects of mercury and the movement and magnification of mercury in a food chain. Use this as an opportunity for review. Tell students that they will be responsible for playing the role of a nutritionist and sharing their knowledge about mercury with a client. The assessment (ASSESSMENT) can be done in class or as a homework assignment.


Alternatively, if using DAY 3 WORKSHEET, reinforce concepts which apply to all biomagnification situations and discuss the consequences in a range of situations (e.g. DDT and the weakening of bird egg shells)

Enrichment Options
Community Connection

Students can make a Fact Sheet about mercury (and fish) to distribute.

Parent-Home Connection

Field Experiences

Test the water in water bodies and homes for mercury and other substances that may accumulate.

Cross-Curricular Extensions

The calculations can be more serious and precise if done in conjunction with the math class. The concept of concentration can also be explored mathematically.

MATH FOLLOW UP can be used in conjunction with the deadly Links game.


Mapping and GIS can be used to locate waterways affected by mercury pollution and the associated fish advisories. It may also be possible to investigate locations where mercury is emitted into the air and map those sites relative to affected waterways.

See for maps of sources of mercuy pollution and state fish advisories.

Stage 4
Teacher Reflection

Author: Elissa Hozore
Modified by: Jean Paul Bibaud, Candice Boone, Ralph Causarano, Tim Gordon, Mike Lashley
Program: EnviroHealth Connections