What is biological magnification?

Biological magnification is the process where the substances like pesticides and heavy metals move up the food chain, they travel their way up in the food chain and at each increasing food chain level, accumulation of toxic substances increases. For example, in a pond water, pesticide DDT was sprayed and the producers were found to have 0.03 ppm concentration of DDT. Since planktons are eaten by small fishes and clams, their body accumulates more DDT than what is found in the planktons. Seagull that feeds on clams accumulates more DDT as one seagull eats many clams. Hawk, the top carnivore, has the highest concentration of DDT.