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The below mentioned article provides a note on bio-magnification, explained with the help of a suitable diagram.
It may be defined as an increase in the concentration of a recalcitrant chemical substance like a pesticide because it is passed to higher members of a food chain. The organ chlorines and some other recalcitrant substances are widely distributed and usually indirectly exposed to the organisms are in very low concentrations, i.e. parts per billion (ppb) ranges. But these low concentrations even are a matter of concern due to a phenomenon known as biological magnification or just bio magnification as abbreviation. It is really very fascinating that aforesaid small amounts in the dissolved form apart from the surrounding water, and being of lipophilic nature become part of lipids of prokaryotes and eukaryotes, both.
.The concentration of these recalcitrant in the cells of the prokaryotic and eukaryotic organisms becomes one to three times more in comparison to surrounding medium. It happens that members of the next higher trophic level ingest these microorganisms. About 10 to 15 per cent of biomass is transferred to higher trophic level and the rest is dispersed in the process of respiration but the persistent lipophilic pollutants are neither degraded nor excreted to a countable amount and thus remain the art of biomass of second trophic level.
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In this way the magnitude of the recalcitrant goes on increasing in the higher trophic levels represented by birds of prey like kites, vultures, eagles, mammalian carnivores, and large predatory fish by a concentration factor of 104 – 106 more than that of the environment (Fig. 35.1).
A biologically active substance like, pesticide may result into serious weakness or even death of the organism. Chlorinated hydrocarbons and DDT have been regarded involved in death and reproductive failure of birds of prey, have reached in the Antarctica even. The chain may be simply represented as pesticide sprayed vegetation →earthworm→ robin breast. Certainly it will be destructive to the bird. Some pesticides have been detected even in the milk of the mother. Some countries have, therefore, banned recalcitrant like DDT.
