biological magnification

(ecology) The increasing concentration of toxins from pesticides, herbicides, and various types of waste in living organisms that accompanies cycling of nutrients through the trophic levels of food webs.

The build-up of toxins from pesticides, herbicides, and domestic and industrial waste such that these toxins are more and more concentrated in living organisms with movement up the trophic levels of food webs. For example, in the 1950s, DDT was used as an insecticide near certain lakes in the USA. The toxin ingested by the midges was absorbed by the fish which ate them, and then by the grebes which lived on the fish, causing a severe decline in the birds' ability to reproduce. The toxins are not easily broken down and hence they accumulate in the organisms at the top of food webs.