Biological magnification occurs when substances are absorbed by organisms higher up in a food chain, leading to higher concentrations of harmful substances like pesticides and heavy metals. The substance must be difficult to break down and not easily degraded by the environment. DDT is a commonly studied substance due to its harmful effects.
Biological magnification, also known as biomagnification or bioamplification, explains why a substance appears in higher concentrations in organisms higher up in a given food chain than in organisms lower in a food chain. This happens because creatures high up in the food chain, such as predators, feed on creatures that are lower in the food chain and absorb substances from the organisms they consume in addition to substances they absorb directly from the environment. In some cases, the biological enlargement process can be harmful to organisms that are at the top of a food chain because they absorb harmful substances from all organisms they consume. While small amounts absorbed from the environment might be completely harmless, the amounts consumed from food sources could add up and be harmful.
Several things must be true of a substance for biological magnification to occur. The substance must be able to be absorbed at some point in the food chain, otherwise it could not be enlarged. It should not be degraded easily by the environment, as this would remove it from the food chain. It must be difficult for organisms to break it down or digest it safely, as digestion would also prevent it from being absorbed by organisms further up the food chain.
While biological enlargement can technically occur with any substance that meets these criteria, it is usually studied due to the enlargement of harmful substances such as fertilizers, pesticides, and heavy metals. Often, these substances accumulate in the body’s fat cells, because they cannot break down and dissolve in water and exit the body in urine. When an organism higher up the food chain consumes a creature lower down the food chain, it absorbs the fat in its intestines. With these fats come the substances previously taken by the other organism and all the harmful effects that these substances can bring with them. Many plants, aquatic and terrestrial, are prone to absorb a variety of substances because they often lack the means to digest them effectively.
One of the main substances scientists study in relation to biological enlargement is the pesticide dichlorodiphenyltrichloroethane, better known as DDT. DDT has had a long and controversial history; it is a very effective pesticide but some studies have shown that it can have a harmful effect on the environment and on human and animal health. It’s also difficult for many organisms to break it down effectively, so it’s often magnified via the food pyramids.
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