Activity 3: Inquiring Further
Biological amplification
Biological amplification is the tendency of pollutants to become concentrated in successive trophic levels. Often, this is to the detriment of the organisms in which these materials concentrate, since the pollutants are often toxic. DDT is a typical example of the effect biocides have on the relationships in a community. For example, at one time, marshes along the north shore of Long Island, New York were sprayed with DDT to control mosquitoes. Later, microscopic organisms in the marsh waters were found to have about 0.04 ppm (parts per million) of DDT in their cells. While this is a low level of poison, no one had expected to find any poison in the organisms. The minnows, clams, and snails that ate these organisms had levels of DDT more than 10 times higher, between 0.5 and 0.9 ppm. The eels, flukes, and billfish that ate the snails and small fish have levels of DDT ranging from 1.3 to 2.0 ppm. The ospreys, herons, and gulls that ate the eels and minnows had levels of DDT between 10 and 25 ppm. Thus, the concentration of DDT in the tissues of the organisms in this food chain increased almost 10 million times from the amount in the seawater and nearly 625 times from the produced level at the bottom of the pyramid to the consumer level at the top.
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