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Tuna for Lunch?

A Case Study Examining Mercury Bioaccumulation and Biomagnification


Caralyn B. Zehnder
Department of Biological & Environmental Sciences
Georgia College & State University


This case examines mercury bioaccumulation and biomagnification within the context of the human health impacts of ingesting food (specifically, fish) contaminated with mercury. It was inspired by a 2009 USGS report on mercury in fish, sediment, and water from streams across the U.S. The case is intended to help students make the connection between an environmental contaminant (mercury, a neurotoxin) and the food they eat. Human activities have been increasing mercury concentrations globally, and coal-burning power plants are the most common source of mercury pollution, a fact many students are unaware of. The case has been used in an introductory level environmental science class (predominantly non-majors), a non-majors general biology class, and a sophomore level ecology class (majors).


  • Explain why there are fish consumption advisories related to mercury.
  • Explain how mercury enters and moves through the environment.
  • Read, interpret, and apply scientific data presented in graphs and tables for this case study.
  • Define biomagnification and explain how it leads to higher concentrations of toxins in animals that are higher up the food chain.
  • Explore how biomagnification occurs in other systems and with other compounds (if students complete optional final activity).


Biomagnification; bioaccumulation; mercury; neurotoxin; fish consumption; tuna; food chain; food web; trophic; coal-burning

Topical Areas


Educational Level

High school, Undergraduate lower division, Undergraduate upper division


PDF, PowerPoint

Type / Methods




Subject Headings

Environmental Science  |   Ecology  |   Biology (General)  |   Limnology  |   Toxicology  |   Public Health  |  

Date Posted


Teaching Notes

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Supplemental Materials

The case includes a PowerPoint presentation (~2.9MB) that can be used in conjunction with the case, as described in the teaching notes for the case.

  Mercury in Fish Power Point

Answer Key

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Mervyn H. Kline
Mercury Pollution Specialist
Clean Air Council

As a former high school environmental science teacher and college professor (biochemist), I found your case history very relevant to the dangers of mercury pollution. There is a very urgent need to get this information into the hands of the next generation of citizens.

You might include the politics and economics of controlling mercury pollution as another component to your case history. It could be used as an extra credit project to further understand how science and politics interact with each other in the real world.

Additional information you might find useful:

  1. The CDC has estimated that as many as 600,000 newborns are at risk from methyl mercury from the fish consumed.
  2. The California gold rush over one hundred years ago used mercury to mine for gold and today mercury is still contaminating rivers and lakes in those mining areas.
  3. The ongoing National Health and Nutrition Examination Survey indicate that people living in coastal areas have higher levels of mercury in their blood than individuals living elsewhere.
  4. Check out the,,, and as well as Dr. Hightower's book "Diagnosis: Mercury, Money, Politics & Poison" (2009).

I hope you will find these comments useful.