ENVIROMENTAL SCIENCE- CASE STUDY
Part II
1. What is in some fish and shellfish that has caused the EPA and FDA to issue the restriction?
2. Why is there a restriction for pregnant women and young children, but not the rest of the population? 3. Do pregnant women have to avoid all fish? Explain your answer.
4. Should Amanda have avoided the pan-seared tuna for lunch?
Part III
1. What human actions lead to increased mercury levels in the environment?
2. How does the mercury end up in fish? Draw a flow chart following the mercury path.
3. Where in the United States are mercury wet deposition levels highest? What do you think explains this pattern?
4. The EPA criterion for human health is 0.3 ug/g. Which fish species have average mercury concentrations that exceed the EPA limits?
5. The concern level for piscivorous (fish-eating) mammals is 0.1 Hg ug/g. Which fish species have average mercury concentrations that exceed this limit? Why is the mercury level for piscivorous mammals lower than the level for human health?
6. Should you be concerned about mercury toxicity if you catch and eat a largemouth bass in a local lake? Why or why not?
7. In which samples were mercury concentrations the highest (fi sh, streams, or sediment)? Why do you think this is?
Part IV
1. Draw a food web for Lake Washington using the species and food preferences given in Table 3. Start with phytoplankton (algae) as the base of your web and then build up the food chain.
2. Label the species in your food chain as either high (>100 ug/kg), medium (20-100 ug/kg), or low (below20 ug/kg) mercury concentrations. Which types of animals have the highest levels of mercury? Which types of animals have the lowest? Why do you think this is?
Final Activity
1. Imagine you are Tara. Write an email to your friend Amanda explaining what you have learned about mercury. Be sure to convey the aspects of your learning that will be most useful to Amanda.
2. Find two other examples of compounds that biomagnify. Explain how each compound and/or toxin enters the biosphere and what impacts it has on living organisms in general and humans in particular.
3. Distinguish between bioaccumulation and biomagnifi cation and design a mnemonic device for the distinction.
