Biomagnification, also known
as bioamplification or biological magnification, is
any concentration of a toxin, such as pesticides, in
the tissues of tolerant organisms at successively
higher levels in a food chain.
3. Biomagnification, also known
as bioamplification or biological magnification, is
any concentration of a toxin, such as pesticides, in
the tissues of tolerant organisms at successively
higher levels in a food chain.
4. This increase can occur as a result of:
•Persistence – where the substance cannot be
broken down by environmental processes
•Food chain energetics – where the
substance's concentration increases
progressively as it moves up a food chain
•Low or non-existent rate of internal
degradation or excretion of the substance –
mainly due to water-insolubility
5. Biological magnification often refers to the process whereby certain substances such as pesticides or heavy
metals work their way into lakes, rivers and the ocean, and then move up the food chain in progressively greater
concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton, which in turn are
eaten perhaps by fish, which then may be eaten by bigger fish, large birds, animals, or humans. The substances
become increasingly concentrated in tissues or internal organs as they move up the chain. Bioaccumulants are
substances that increase in concentration in living organisms as they take in contaminated air, water, or
food because the substances are very slowly metabolized or excreted.
Biomagnification of toxins in the food chain of a terrestrial environment. The dots represent the
organic molecules present in each trophic level. The crosses represent the mercury present in each
trophic level. While dots remain relatively constant in each individual, the concentration of crosses
become greater in each preceding trophic level. Biomagnification: An increase of toxin concentration
as the food chain moves up to higher levels. Organisms at the top have a higher tissue concentration
of toxins and pollutants than lower levels. The concentration system is due to persistence of the
toxins, food chain energetics, and low rate of internal degradation or excretion of the
substance.Trophic level I represents the primary producers. Trophic level II represents the primary
consumers. Trophic level III represents the secondary consumers. Trophic level IV represents the
tertiary consumers.
6. Causes of Biomagnification
1. Products Used in Agriculture: Chemical used in the agriculture sector is highly toxic and plays a pivotal
part in biomagnification. Examples of such chemicals are various pesticides, herbicides, fungicides, and
different inorganic fertilizers. Ultimately these chemicals penetrate the soil and then are carried to rivers and
oceans via surface runoff. As a result, they enhance the biomagnification definition of causing harm to an entire
food chain.
2. Industrial Activities: Toxic by-products released by various industries are a significant cause of
biomagnification. Additionally, the gas emission by them pollutes the air and harms the ecosystem even further.
3. Organic Contaminants: Organic substances like manures and biosolids contain essential nutrients such as
carbon, nitrogen, and phosphorus. Plants primarily use these. However, the industrial use of these substances
causes biomagnification.
4. Mining: Mining produces by-products like copper, cobalt, zinc, lead and several other toxic chemicals.
These substances are then deposited in soil and water resources and subsequently contaminate them.
7. Substances that biomagnify:
There are two main groups of substances that biomagnify. Both are lipophilic and not easily degraded.
Novel organic substances are not easily degraded because organisms lack previous exposure and have
thus not evolved specific detoxification and excretion mechanisms, as there has been no selection pressure
from them. These substances are consequently known as "persistent organic pollutants" or POPs.
Metals are not degradable because they are elements. Organisms, particularly those subject to naturally
high levels of exposure to metals, have mechanisms to sequester and excrete metals. Problems arise when
organisms are exposed to higher concentrations than usual, which they cannot excrete rapidly enough to
prevent damage. Some persistent heavy metals are especially dangerous and harmful to the organism's
reproductive system.
Novel organic substances:
•DDT (dichlorodiphenyltrichloroethane)
•Hexachlorobenzene (HCB)
•PCBs (polychlorinated biphenyls)
•Toxaphene
•Monomethylmercury
8. A real-life example of biomagnification is –
•When a marsh is sprayed to control mosquitoes, it releases a trace amount of DDT. When mixed with water, it
accumulates in the cell of various aquatic organisms.
•Once feeders up the food chain, such as clams and fishes, eat these organisms, they consume that DDT.
Moreover, the concentration of DDT is ten times greater compared to the previous stage.
•This concentration of DDT moves up the food chain from one tropic level to another. For instance, if a seagull
consumes one such fish, it will accumulate more DDT. According to studies, there was a 1000 times increase in
the concentration of DDT in phytoplankton as compared to the concentration in water, 13 times higher in
zooplankton as compared to phytoplankton, around 40 times higher in different fishes as compared to
zooplankton and 25 times higher in fish-eating birds compared to fishes. DDT affects the calcium metabolism of
birds and results in the thinning of eggshells.
•During the 1940s and 1950s, DDT was extensively used to decrease the mosquito population and this led to a
rapid decline in the bird population.
•Another prominent biological magnification example is the presence of mercury in various predatory fishes.
Fishes like swordfish, shark, tuna, orange roughy, king mackerel, etc., contain a higher level of toxic mercury
than smaller fishes.
9.
10. Effects of Biomagnification
•A significant effect of biological magnification is noted on human health. For
instance, in recent years, a large number of individuals who have consumed
seafood regularly have been diagnosed with cancer. The reason behind such a
phenomenon is the presence of mercury.
•Other noted biomagnification effects are reproduction and development of all
animals, destruction of coral reefs, and most significant disruption in the natural food
chain and the ecosystem.
11. References:
1.Silvy, Nova J., ed. (2012). The Wildlife Techniques Manual: Research. Vol. 1 (7th ed.). Baltimore,
Maryland: The Johns Hopkins University Press. pp. 154–155. ISBN 978-1-4214-0159-1.
2.^ Landrum, PF and SW Fisher, 1999. Influence of lipids on the bioaccumulation and trophic transfer
of organic contaminants in aquatic organisms. Chapter 9 in MT Arts and BC Wainman. Lipids in fresh
water ecosystems. Springer Verlag, New York.
3.^ Croteau, M., S. N. Luoma, and A. R Stewart. 2005. Trophic transfer of metals along freshwater
food webs: Evidence of cadmium biomagnification in nature. Limnol. Oceanogr. 50 (5): 1511-1519.
4.^ EPA (U.S. Environmental Protection Agency). 1997. Mercury Study Report to Congress. Vol. IV: An
Assessment of Exposure to Mercury in the United States . EPA-452/R-97-006. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards and Office of Research and
Development.
5.^ "DDT Ban Takes Effect". United States Environmental Protection Agency. 1972-12-31. Archived
from the original on 2014-08-12. Retrieved 2014-08-10.
6.^ Suedel, B.C., Boraczek, J.A., Peddicord, R.K., Clifford, P.A. and Dillon, T.M., 1994. Trophic transfer
and biomagnification potential of contaminants in aquatic ecosystems. Reviews of Environmental
Contamination and Toxicology 136: 21–89.
7.^ Gray, J.S., 2002. Biomagnification in marine systems: the perspective of an ecologist. Mar. Pollut.
Bull. 45: 46–52.
