Minds On:

1. Minds On: • Videos: Methyl Mercury and DDT

2. Bioaccumulation and Biomagnification Tracing Pollution Through An Ecosystem

3. We can represent pollution in an ecosystem using colored dots.

4. Bioaccumulation • The increase in concentration of a substance in an organism over time • The substance must be taken in and stored faster than it is broken down by the body • Through things that are eaten or breathed in • Absorbed through skin or roots and leaves • Examples: • DDT (and other pesticides) • Methyl Mercury (and other industrial pollution) • Effects: • Cancer and Birth Defects, • Other changes in body chemistry

5. Biomagnification • The increase in concentration of a pollutant from one link in the food chain to another • Eating contaminated food “magnifies” the effect of bioaccumulation. • Tracking through the use of colored dots: • Producers suffer from only bioaccumulation and receive one dot. • Consumers suffer from both bioaccumulation and biomagnification and receive an extra dot for each increase in trophic level.

6. Example - DDT • Benefits • Low toxicity for humans • Highly effective against insects • Easy and cheap to manufacture • Problems • Remains active in the environment for a long time • Causes shell thinning in birds and other reproductive problems • Status • Banned for use in North America since the 1960’s • Still used in the 3rd World to fight malaria (carried by mosquitoes) • Saves 1000’s of human lives each year

7. http://www.youtube.com/watch?v=-UiCSvQvVys • http://www.youtube.com/watch?v=E5P-UoKLxlA • http://www.youtube.com/watch?v=kyYpwOTtaLI • http://www.youtube.com/watch?v=LQ64sV0nSVU

8. Practice • Create the following food web: • Kelp(seaweed) is eaten by sea urchins and krill • Sea urchins are eaten by sheephead fish and wolf eels • Krill are eaten by sardines • Sardines are eaten by sharks • Show how methyl mercury bioaccumulates in the kelp and biomagnifies through the food web. • Which organism ends up with the highest concentration of methyl mercury?