Food chain studies help us to understand the feeding relationships and the interaction between organisms in any eco-system. They help us to understand the energy flow mechanism and matter circulation, such as circulation of toxic substances in the eco-system and the problem of biological magnification.
Biological magnification is the tendency of pollutants to get concentrated in successive tropic levels. Large concentration of pollutants could be detrimental if they are toxic.
Bio-magnification occurs when organisms at the bottom of the food chain accumulate the toxic materials greater than that available in the environment around it.
As DDT, heavy metals and other toxic metals resemble essential inorganic nutrients these will also be taken up by plants along with the essential nutrients.
If there is a shortage of essential nutrients, accumulation of these toxic materials will be more and more. This is the first step of bio-magnification and is known as 'bio- accumulation'.
The second step of bio-magnification occurs when the producers are eaten by consumers. It is known, that energy availability decreases from one tropic level to the other.
Thus, successive tropic levels consume more and more biomass and accumulate more and more toxic materials.
Since these toxic substances are not broken down in the body or excreted easily, they quickly get accumulated in the tissues. The case is severe for toxic materials soluble in fat such as DDT.
When producers containing DDT get digested by the consumers, the DDT solubilizes in fat and gets stored. When this consumer is eaten by another consumer, its fat is digested and the pollutants move to the fat of the new consumer.
In this way, the toxic substances are built up in fatty tissues of consumers. For water-soluble toxic materials, bio- magnification however, cannot occur as they are dissolved in the body fluids of consumers and get excreted easily.
Since man is an omnivore and has access to all tropic levels for food, he receives the toxic substances in his body in large amounts. Secondary and tertiary consumers located on top of the food chain also accumulate toxic materials in their body.
The bio-magnification of pollutants can be estimated with the help of Biological Concentration Factor (BCF).