Diane Kelly                                                                                                                    Return to Earth Sciences Menu

Cunningham JHS (IS 234-K)

Summer 2001

What type of organism would be best to test for the bioaccumulation of PCB's in an estuary?

Warm up: Separate class into groups of 5.  Give them handouts on the ecosystem of an estuary or have them research on the web.  Using the "Estuary Worksheet" they should answer the following: What type of water is found in an estuary?  Have them define the three main sections of the water in an estuary and give an example of an organism that lives in each.  Have them draw a cross section of the water labeling the three main sections and what type of water would be found on the top and on the bottom.

Review and discuss their results.  Display drawings, check for accuracy.

Discussion:

What are PCB's?  Polychlorinated biphenyl- organic pollutants

Where do they come from?  They were used to cool down transformers, and as insulators.

Why are thy no longer used?  They are thought to cause cancer and brain defects.

Why are they still in the environment?  They have a long half-life (30 yrs)

How do they get absorbed?  They are hydrophobic-(see if they can figure out the meaning by taking the word apart) they do not mix with water, they are absorbed by fats.

What do we need to test to see if the water is contaminated?  The organisms that have fatty tissue, NOT the water.

Biomagnification- as you move up the food chain the higher the concentrations of pollutants.

Have groups discuss what organism would be best to test for bioaccumulation of PCB's.   Have them choose from which main areas-plankton, necktonic, benthic.  Use Graphic organizer.  Discuss and list the pros and cons' of each.  The class should come to a conclusion that benthic organism are best because they stay in a small area and some are filter feeders.