Exercises: Persistent Pollutants and Biomagnification

Define persistent organic pollutant (POP). Give one example, such as DDT or PCBs.

Distinguish bioaccumulation from biomagnification in one or two sentences each.

In an aquatic food chain (algae, small fish, large fish, osprey), which organism would you expect to have the highest concentration of a biomagnifying pollutant? Why?

DDT was widely sprayed in the mid-1900s, and bald eagles and ospreys later declined. Explain how DDT moved through food chains and how it affected the birds' reproduction.

A pollutant is measured in a lake food chain.

(a) Calculate how many times more concentrated the pollutant is in large fish than in phytoplankton.

(b) Explain what the data show about biomagnification.

Mercury from coal-burning power plants ends up in lakes and builds up in fish. Explain why a health agency might advise pregnant women to limit eating large predatory fish such as swordfish more than small fish such as sardines.

A researcher measures PCB concentrations in a Great Lakes food web.

(a) Calculate the factor of increase from algae to herring gull eggs.

(b) Explain why the increase occurs at each step, using the properties of PCBs.

(c) Predict how a ban on PCB production would change these values over time, and explain why recovery may be slow.

A city must choose between two pesticides for mosquito control. Pesticide X is cheap, kills many insects, breaks down slowly, and dissolves in fat. Pesticide Y costs three times as much, targets mosquito larvae, and breaks down in days.

(a) Predict which is more likely to biomagnify, and justify your answer.

(b) Describe two possible ecosystem effects of the choice.

(c) Recommend one option and explain how you weigh cost against ecological risk.