Question

What is biomagnification? Explain with the help of a food chain.

Answer 1

The concentration of a toxin, such as pesticides, in the tissues of tolerant organisms at successively higher levels in a food chain is termed as biomagnification, also known as bio amplification or biological magnification. The trophic enrichment of contaminants within food webs is termed as food web biomagnification. It refers to the progressive increase in chemical concentrations with increase in animal trophic status.

Complete answer:
When industrial, agricultural, and human wastes run off or are deliberately discharged into rivers which then empty into the sea, toxic chemicals and heavy metals build up there. These kinds of toxic pollutants can cause various diseases, birth defects, genetic mutations, reproductive difficulties, and even death in many kinds of marine organisms. The damage severity varies greatly between species. Mostly, the animals that are near to the top of the food chain are affected badly because of the process called biomagnification.
The condition where the chemical concentration of an organism exceeds the concentration of its food when the major exposure route occurs from the organism’s diet is termed as biomagnification.
Biomagnification can be further explained using the example of DDT in water:
To control mosquitoes, when marsh is sprayed, trace amounts of DDT get released. It gets accumulated in the cells of various aquatic organisms when mixed with water.
When feeders up on the food chain such as clams and fishes once eat these organisms, that DDT gets consumed by them. At this time, the concentration of DDT gets ten times greater compared to the previous stage.
This DDT concentration moves up the food chain, from a trophic level to another. For example, if a seagull consumes one of such fish, more DDT gets accumulated in them. The concentration can go up to $40$ times or more compared to the previous fish. Therefore, the concentration is about $400$- fold increase in this rather short food chain.
This DDT can also get accumulated in humans by the following food chain:
$Phytoplankton{\text{ }} \to {\text{ }}Zooplankton{\text{ }} \to {\text{ }}Small{\text{ }}fish{\text{ }} \to {\text{ }}Big{\text{ }}fish{\text{ }} \to {\text{ }}Human.$

Note:
Many governments have slowly started to realize the importance of eliminating the negative impacts of these pollutants. In the United States, production of DDT was banned at the year $1972$, and more chemicals have been banned since then. The Stockholm Convention on Persistent Organic Pollutants came into effect on $2004$ which internationally banned the production of PCBs and other harmful chemicals.