Biomagnification: Meaning, Example, Causes, Effects, Topics

Biological magnification or biomagnification is the accumulation of harmful chemical substances, pesticides or heavy metals, to higher trophic levels of a food chain. Such toxins become more concentrated in their amount as they pass up the food chain and result in threats of severe health conditions to the top predators, including humans. This topic is included in the Class 12 chapter Environmental Issues in Biology.

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This Story also Contains

1. Biomagnification Definition
2. What is Biomagnification?
3. Biomagnification Causes
4. Biomagnification Process
5. Pollutants Associated with Biomagnification
6. Effects of Biomagnification

Biomagnification Definition

Biological Magnification or Biomagnification is the process by which the concentration of toxic substances increases in organisms at each successive level of the food chain.

What is Biomagnification?

Biomagnification is the accumulation of harmful substances, pesticides, and heavy metals at every step in the food chain. Such pollutants cannot be decomposed and therefore accumulate within an organism's tissues. The toxins are accumulated by small organisms, and then through a food chain if a larger animal feeds on them, their concentration will increase the toxin levels within the top predators. This results in serious health and environmental problems.

Also Read:

• Environmental Issues
• Types of Pollution
• Algal Bloom
• Biodiversity and Conservation

Biomagnification Causes

The major factors contributing to biomagnification are human activities that release persistent pollutants into the environment. Some of these pollutants include:

• Pesticides: Pesticides that farmers use in large quantities, such as DDT, can greatly enhance yields but might also run off to streams and be taken up by aquatic organisms. Most of these chemicals are generally resistant to degradation and tend to accumulate in food chains.

• Heavy Metals: Heavy metals such as mercury and lead are also emitted into the environment through industrial processes, mining, and dump waste. These metals are very toxic and once released into the atmosphere can stay for a long time. On ingestion, they get absorbed and stored in the tissues of the organisms, which

• Industrial Chemicals: By-products such as polychlorinated biphenyls and other POPs are released from manufacturing and other related industries. They are hydrophobic, therefore they tend to accumulate in the fatty tissues of living organisms.

• Agricultural runoff: This generally occurs due to fertilizers and other chemicals used during agriculture that leach into rivers and lakes, thus contaminating aquatic ecosystems. The absorbed pollutants proceed upwards from the first level of energy throughput.

• Improper Waste Disposal: Chemicals at dumped sites and untreated waste materials contaminate the environment, putting into food chains a wide range of hazardous substances responsible for biomagnification.

Biomagnification Process

Biomagnification is a process wherein there is downward transmission and eventual concentration of pollutants in the food chains and webs, resulting in large ecological and health impacts.

Trophic Levels

An ecosystem consists of various trophic levels. The base includes producers (plants), followed by primary consumers (herbivores), then secondary consumers (carnivores), and finally tertiary consumers, which are the top predators. All these steps offer a ladder for energy and nutritional flow in the food chain.

Steps of Biomagnification

• Various sources link pollutants entering the ecosystem through water, soil, and air.

• These are then absorbed by organisms at the lower trophic levels, for example, plankton and small fish.

• Since these organisms are consumed, it progresses to increasing the concentration of pollutants as they go up the food chain.

• The top predators have the highest concentrations and, therefore, suffer the most devastating effects of biomagnification.

Pollutants Associated with Biomagnification

Some of the pollutants responsible for biological magnification are mainly from human activities and industrial processes.

Common Pollutants

• Pesticides: The best-known example is DDT, which was largely used to eradicate mosquitoes from communities but was later discovered to be a harmful chemical to the environment.

• Heavy Metals: Mercury and lead are two metals that accumulate in the environment and pose significant health threats.

• Industrial Chemicals: PCBs are utilised in electromechanical devices apart from other industrial applications but have recently been identified as highly toxic environmental pollutants.

Sources of Pollutants

• Agricultural use of chemical fertilizers and pesticides is washed into the water leading to the pollution of aquatic habitats.

• Factories and industrial plants largely release untreated or poorly treated wastes into the environment.

• This leads to pollutants entering the soil and water due to the dumping of hazardous wastes without treating them.

Effects of Biomagnification

Biomagnification affects wildlife, human health, and total ecological balance.

Effects on Wildlife

The classic example is the thinning of eggshells of birds owing to the DDT content. Due to this, the bird population declined since the eggs were too fragile to withstand.

Effect on Human beings

High levels of mercury neurologically damage an organism, while PCBs are known to be associated with cancer and other serious health effects. Long-term exposure to these kinds of biomagnified pollutants can result in serious health problems, such as developmental and reproductive impairment.

Ecological Effects

Population declines in top predators caused by toxic levels can further upset the balance in ecosystems.

Toxic pollutants can have stressful effects on sensitive species, provoking their decline or even extinction and reducing the general biodiversity.

Effects on Marine Animal Development and Reproduction

The accumulation of hazardous substances in aquatic species' vital organs interferes with reproduction and development.

Sea bird eggs, for instance, have fragile shells that the birds themselves could destroy during incubation. Toxic chemicals, mercury, and selenium kill the reproductive organs of aquatic animals.

Coral reef destruction

The primary factor destroying coral reefs is the use of cyanide in fishing and gold leaching. Numerous marine organisms live on and feed on coral reefs. Their destruction affects the lives of many aquatic animals.

Disruption of the Food Chain

The chemicals and toxins released into the water bodies disrupt the food chain. The tiny organisms absorb the toxins that larger animals eat up. These toxins, thus, accumulate in the higher level of organisms.

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