Biomagnification – UPSC Environment Notes

“Biomagnification, also known as biological magnification, involves the accumulation of specific chemicals in living organisms at concentrations surpassing those found in the inorganic, non-living environment.”

What is Biomagnification?

“Biomagnification, characterized by the escalation of contaminated substances due to an intoxicating environment, encompasses the accumulation of heavy metals like mercury and arsenic, as well as pesticides such as polychlorinated biphenyls and DDT.

These substances are absorbed by organisms through their dietary intake. As organisms in the upper echelons of the food chain consume those in the lower tiers containing these toxins, the toxins amass in the higher-level organisms.

Let’s delve into the causes and consequences of biomagnification.”

Process of Biomagnification

  • Involves toxic chemicals and pollutants like heavy metals, pesticides, and polychlorinated biphenyls (PCBs)
  • Progresses through the food chain
  • Travels from the environment into soil or water systems
  • Ingested by aquatic animals or plants
  • Consumed by animals, humans, and large birds
  • Slow elimination or metabolic breakdown leads to an increase in concentration in organisms up the food chain

Release of Toxic Chemicals & Pollutants Into the Environment

Toxic chemicals and pollutants are discharged into the environment, gradually infiltrating soils, rivers, lakes, and seas. In diverse habitats, the concentrations of these harmful compounds and contaminants initially seem low, even in terms of weight, as they are exceedingly small.

Entry of Toxins Into Phytoplanktons

Small floating plants in the sea, responsible for absorbing pollutants, are termed phytoplankton. Once absorbed, toxins persist in their body tissues without undergoing elimination or breakdown. Over time, these toxins accumulate in significant quantities, reaching up to 200 parts per trillion, resulting in a fourfold increase in toxin accumulation.

Entry of Toxins Into Zooplanktons

  • Small marine invertebrates floating in seas are called zooplankton.
  • They consume phytoplankton and absorb the associated poisons.
  • Toxins remain trapped in the organism’s tissues, resisting elimination or breakdown.
  • Over time, toxin concentration rises to two parts per billion, marking a tenfold increase.

Consumption of Zooplanktons by Small Fishes

  • Little fish, upon consuming zooplanktons, absorb the poisons.
  • These toxins are then absorbed into their fatty tissues, resulting in a buildup.
  • Concentrations escalate to around 20 parts per billion, representing a tenfold increase.

Consumption of Small Fishes by Larger Ones

  • When larger fish feed on smaller ones, they ingest the accumulated poisons in fatty tissues.
  • Concentrations increase to 80 to 100 parts per billion, indicating a four to fivefold rise.

Organisms on Top of the Food Chain

  • At the top of the food chain, species like dolphins, sea birds, and humans accumulate poisons in their tissues, especially the liver.
  • Concentrations peak at 10,000 to 15,000 parts per billion.
  • Adverse effects on essential organs affect fertility and increase susceptibility to infections.

Causes of Biomagnification

Here are the major causes of biomagnification:

  1. Agriculture: Agricultural pesticides, insecticides, fertilizers, and fungicides, containing trace amounts of heavy metals such as mercury, arsenic, copper, lead, and cadmium, are highly toxic. Released into the soil, rivers, lakes, and seas, these substances contribute to health issues in aquatic organisms and humans.
  2. Organic Contaminants: Industrially processed manures and biosolids carry contaminants like pharmaceuticals and personal care products, adversely affecting the health of humans, animals, and wildlife.
  3. Industrial Activities: Toxic substances released by industries and factories into the soil, lakes, oceans, and rivers, coupled with gaseous emissions, pollute the environment and enter the food chain, initiating biomagnification.
  4. Mining Activities in the Ocean: Deep-sea mining for metals like zinc, aluminium, cobalt, silver, and gold results in the generation of substantial amounts of selenium and sulphide. These deposits in water wreak havoc on oceans and coastal regions, escalating the level of toxicity. Aquatic organisms higher in the food chain absorb these toxic substances, contributing to biomagnification.

Effects of Biomagnification

Here are the effects of biomagnification on living organisms and the environment:

  • Impact on Human Health: Biomagnification renders humans more susceptible to ailments such as cancer, kidney problems, liver failure, birth defects, respiratory disorders, and heart diseases.
  • Effects on Reproduction and Development of Marine Creatures: Toxic chemicals accumulate in vital organs of aquatic organisms, adversely affecting their reproduction and development processes.
  • For example, the eggshells of sea-birds become excessively thin, risking self-crushing during incubation. Reproductive organs of aquatic creatures are damaged by toxic chemicals like mercury and selenium.
  • Destruction of Coral Reefs: The use of cyanide in gold leaching and fishing is a primary cause of coral reef destruction. Coral reefs serve as habitat and feeding grounds for numerous sea creatures, and their demise has widespread consequences for aquatic life.
  • Disruption of Food Chain: Chemicals and toxins released into water bodies disrupt the food chain. Small organisms absorb toxins, which are then consumed by larger animals. Consequently, these toxins accumulate in higher-level organisms.

Difference Between Biomagnification and Bioaccumulation

DefinitionChemical compounds or poisons accumulate at higher trophic levels of a food chain. Higher concentration of chemical compounds in animals.Toxic substances build up in the tissue of a certain organism.
Food ChainBiomagnification occurs between two trophic levels.Bioaccumulation, like Biomagnification, occurs at the trophic level.
CausesNumber of stages rises as one progresses up the food chain.Increase in a substance’s concentration within the organism.
Level of concentration of pollutantCauses a pollutant’s concentration in an organism to rise.Toxicant concentrations rise as they progress from one trophic level to the next.
ExamplePollutants and toxins absorbed by microscopic aquatic animals passed on to small fish, then eaten by larger fish and other aquatic species.Mercury builds up in aquatic animals.


Biomagnification poses a significant threat to humans, aquatic creatures, and the environment. Measures should be implemented to curb the use of toxins or explore suitable alternatives. Biomagnification serves as a valuable tool for gauging the quantity of contaminants in a particular area. This pollution data, consequently, unveils critical insights into the impact on populations and ecosystems.

FAQs on Biomagnification

Question: What is the biomagnification process?

Answer: Biomagnification is the process where certain pollutants or toxins accumulate in increasing concentrations as they move up the food chain. It occurs when organisms at higher trophic levels consume those lower down, leading to a magnification of pollutant concentrations.

Question: Why is biomagnification essential in toxicology?

Answer: Biomagnification is crucial in toxicology because it helps assess the increasing concentration of harmful substances in organisms at higher trophic levels. This process aids in understanding the potential risks and impacts of pollutants on ecosystems, human health, and wildlife.

Question: How do you calculate biomagnification?

Answer: Biomagnification is often calculated using the biomagnification factor (BMF), which is the ratio of the concentration of a specific substance in an organism at a higher trophic level to that in its prey or lower trophic level. The formula is BMF = Concentration in higher trophic level organism / Concentration in lower trophic level organism. A BMF greater than 1 indicates biomagnification.

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