Biomagnification

Biomagnification refers to the increase in concentration of a substance that enters the food chain and get accumulated into the tissues and organs of an organism and then subsequently moves to higher levels of food chain. In this article, you will get information about Biomagnification, its definition, difference between biomagnification and bioaccumulation, causes and effects for                 , providing key insights for GS Paper-III Environment and Ecology section of UPSC IAS Exam.

Table of Content

• Table of Content              
• What is Biomagnification?           
• Features of Biomagnification      
• Process of Biomagnification with an example:     
• Causes of Biomagnification         
• What is the difference between Bioaccumulation and Biomagnification? 
• Substances causing Biomagnification:     
• Effects of Biomagnification          
• Effective Solutions to Biomagnification   
• Conclusion         
• Frequently Asked Questions       
• Reference           

What is Biomagnification?

• Biomagnification refers to the process by which there is an increase in concentration of a substance, like a pesticides or heavy metals that enters the food chain and get accumulated into the tissues and organs of an organism and then subsequently moves to higher levels of food chain.
• Examples of Biomagnification based substances are DDT, Dichlorodiphenyldichloroethylene (DDE), Polychlorinated biphenyls (PCBs), toxaphene, and the organic forms of mercury and arsenic in nature.
• Biomagnification is also known as bioamplification or biological magnification.
• Biomagnification occurs when the concentration of any harmful substance (e.g., DDT (dichloro-diphenyl-trichloroethane)) starts building up in a food chain.
  • The concentration of DDT in parts per million increases with each trophic level.
  • Biodilution is a process that causes a decrease in the concentration of a pollutant as it moves up the food web in an aquatic environment and is the opposite of biomagnification.

Features of Biomagnification

• Many chemicals that undergo bioaccumulation are soluble in fats (lipophilic) but insoluble in water (hydrophobic).
• The lipophilic substances cannot be easily diluted, broken down, or excreted via urine.
  • Result: they accumulate in the fatty tissues of organisms if the organisms lack the enzymes to degrade them.
• When a predator consumes prey, it absorbs the fats that contains these substances, resulting in their accumulation in predator’s bodies.
• Due to energy loss at each level of the food chain, predators need to consume multiple prey, including their lipophilic substances.
  • Result: the predators tend to have higher levels of concentration than their prey.
  • Biomagnification is highest in secondary consumers.
• The substance cannot be broken down by environmental processes hence it persists in the environment and are absorbed by the organisms consuming such foods.

Process of Biomagnification through an example:

• The seawater contains only small amounts of mercury but algae absorbs it as methylmercury, which is highly toxic.
• Organisms consuming such algae efficiently absorb methylmercury but excrete it very slowly.
• This leads to bioaccumulation and bioconcentration in the adipose tissue of successive trophic levels, such as zooplankton, small nekton, and larger fish.
• Predatory fish and birds like swordfish, sharks, ospreys, and eagles that consume these fish end up with higher concentrations of mercury in their tissues than what direct exposure alone could account for.
  • This has caused the decline of North American predatory bird populations in the 1950s, as DDT caused thinning of eggshell due to biomagnification.
• If a whole group of organisms dies due to such toxins, it would disrupt the natural flow of the food chain.
  • This disruption may have long-term effects that might not be immediately noticeable.

DDT as a Bio Magnifier:

• DDT was recognized as harmful to the environment by many organizations.
• DDT is highly insoluble and accumulates in adipose tissue, resulting in progressive biomagnification as predators consume fat containing DDT.
• The detrimental effects of DDT biomagnification were observed when there was decline of bald eagles and peregrine falcons.
  • Result: DDT was banned in many parts of the world including in India in 1972.

Causes of Biomagnification

Agricultural products:

• Chemicals used in agriculture, such as herbicides, pesticides, fungicides, and inorganic fertilizers, contain highly toxic substances that can lead to biomagnification.
• These chemicals accumulate in the soil and can find their way into rivers and lakes through surface runoff during storms.
  • The resulting Eutrophication and Biomagnification causes death of many aquatic organisms.
• Industrial effluents and agricultural waste together contributes towards biomagnification.
• These substances contain traces of heavy metals like lead, copper, arsenic, mercury, and cadmium.
• Toxic chemicals and heavy metals are absorbed by zooplankton and plants in water and soil, respectively and then the process of biomagnification begins.

Organic contaminants:

• Organic substances such as biosolids and manures contain essential nutrients like nitrogen, phosphorous, and carbon that plants need.
• Organic manure processed in industries may contain toxic chemicals and heavy metals, which are absorbed by primary consumers and accumulate in other organisms.

Plastic pollution:

• Plastic contains a harmful chemical called Bisphenol A, which is released into water bodies.
• When fish ingest such plastic particles, these particles get accumulated in other organisms in the food chain.

Mining:

• During mining activities, substances like zinc, copper, cobalt, lead, and other chemicals can be released into water bodies and adjacent farmland.
• These mineral deposits become highly toxic when absorbed by aquatic animals and crops.
• These toxic metals accumulate in organisms at lower trophic levels, and as they are consumed by higher trophic level organisms, the metals accumulate in different levels of the food chain.

Toxic gases and air pollution:

• The release of gases into the environment, such as vehicle exhaust and emissions from oil manufacturing and refining industries also contributes to biomagnification.
• These gases get dissolved in rainwater and fall as acidic rain, which is then consumed by the primary producers.

What is the difference between Bioaccumulation and Biomagnification?

Substances causing Biomagnification:

• For biomagnification to occur, the pollutant must possess certain characteristics such as it should be long-lasting, mobile, and biologically active.
  • If pollutant is immobile, it will remain in one place and will not be absorbed by organisms.
  • Water-soluble pollutants are typically excreted by organisms.
  • Pollutants that get dissolved in fats can be retained for long-period.
• Biomagnification is observed in two common groups of substances:
  • Chlorinated hydrocarbon is also known as organochlorines.
  • Inorganic compounds such as methylmercury or heavy metals.
• These substances possess lipophilic properties and are resistant to degradation.
• Novel organic compounds like organochlorines are not degraded by the organisms as organisms have not been previously exposed to them and thus lack specific detoxification and excretion mechanisms.
  • As a result, these substances are referred to as “persistent organic pollutants” or POPs.
• Unlike organic compounds, metals cannot be degraded as they are chemical elements.
• Organisms that are regularly exposed to high levels of metals, have developed mechanisms to sequester and excrete metals.
• Problems arise when organisms encounter higher concentrations than usual and exceed their ability to eliminate them promptly, leading to potential harms.
• Persistent heavy metals such as lead, cadmium, mercury, and arsenic can cause various detrimental health effects across different species.

Effects of Biomagnification

Human Health:

• The consumption of seafood has been associated with specific types of cancer as mercury and Polycyclic Aromatic Hydrocarbons gets accumulated in the tissues of marine organisms.
• Mercury effects human health by causing damage to the nervous system, impaired vision, hearing, walking, and speaking, involuntary muscle movements, and damage to the skin and mucous membranes.
• Consuming plants or aquatic animals that have absorbed heavy metals and toxic substances can lead to long-term health issues, including cancer, kidney failure, respiratory problems, brain damage, birth defects, and heart diseases.
• Fishes living in heavily polluted areas often contain traces of highly toxic mercury and lead, which can be harmful when ingested by humans.
• Pregnant women when consumes such seafood can result in mental problems and mutations in their infants.

Effect on Aquatic Animals:

• The ingestion and accumulation of metals in the tissues of marine organisms negatively impact their development and reproduction.
• Heavy metal consumption for example in seabirds can affects their egg production.
• The eggs have thin and fragile shells that are easily broken during incubation.
• Toxic chemicals like selenium and mercury can also damage the reproductive systems of fish when water bodies become contaminated.
• Few fish populations can disrupt the food supply for other creatures that rely on them for survival.
• Water bodies with high concentrations of Polychlorinated biphenyls (PCBs) have a similar effect on aquatic animals.

Effective Solutions to Biomagnification

Elimination of the use of some heavy metals:

• Toxic substances like lead, arsenic, and mercury should be strictly prohibited and completely phased out from the manufacturing of products such as petroleum.
• Their usage in petroleum products and other industries must be banned.
• The coal industry must develop innovative strategies to eliminate mercury emissions.

Cleaning of contaminated areas:

• Contaminated areas exposed to toxic metals should be thoroughly cleaned.
• The government should identify areas contaminated with solid and medical waste incinerators and close them down.
• These areas should be replaced with waste reduction programs, and efforts should be made to treat and rehabilitate the soil for future use.

Role of institutions using toxic substances:

• Health sectors, particularly dental departments, should eliminate the use of mercury-containing items and opt for safer alternatives.
• The government should remove and securely store mercury-containing thermostats and thermometers.

Wood work:

• Woodworking industries should avoid using additives like Chromated copper arsenate (CCA) and Ammonia Copper Zinc Arsenate (ACZA), which contain highly toxic arsenic.

Watch out for lead paints:

• Homes built before the 1980s are likely to have toxic lead paints.
• Water sources should be covered to prevent lead dust contamination while removing such paints.

Avoid using PVC:

• When purchasing plumbing materials, avoid PVC as it contains lead that can contaminate drinking water and the environment.
• If PVC is already installed, refrain from using hot water immediately after opening the tap, as it may contain traces of lead.

Other solutions:

• Proper disposal of cooking oil, grease, household chemicals, and medications is essential.
• When doing laundry, use phosphate-free bleaches and soaps that do not contain metal traces.

Conclusion

Biomagnification poses significant environmental risks and has detrimental effects on both wildlife and human health. The consequences of biomagnification can be huge and long lasting, thus some immediate steps should be taken by the Government of each country to stop any release of such substances in the place where they can enter the food chain and get accumulated.

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FAQs (frequently asked question)