Biological Magnification (Biomagnification)

Introduction

Chemicals are necessary for living beings to live a disease-free and healthy life. But, when non-essential chemicals enter and accumulate in the body of living organisms, it can be harmful to them. Biomagnification refers to a condition where the chemical concentration in the body of a living being extends too much. The path of chemicals entering the body of living beings is often via the food web and the level of concentration increases with the increase of successive trophic levels. Biomagnification refers to this increase of chemical concentration in the body of living organisms via the food web.

Image 1: Bio-magnification in a pond ecosystem: A pond has been intoxicated with chemicals that

Biological Magnification− Meaning and its Features

Biological magnification refers to the accumulation of non-essential and harmful chemicals in the body of living organisms at different levels of the food chain. The process of biomagnification starts when industrial, human, and agricultural waste is allowed to mix with oceans. It usually occurs when the waste materials find their way into the ocean via sewers, rivers, and water streams.

Image 2: Mercury Food Chain: Figure shows some common sources of mercury, the conversion to toxic methylmercury and the outline of EPA consumption recommendations for certain types of fish based on mercury levels.

• The dangerous waste chemicals thereby get deposited on the sea bed. The fishes that are bottom feeders eat these chemicals and these chemicals start accumulating in their bodies. It then is carried forward to the top levels of the food chain.

  For example, human beings are at the top of the food chain and when they consume food rich in these harmful chemicals they are exposed to magnified concentrations of the chemicals in their own bodies.

• The notable feature of biomagnification is that with every step of increasing the food chain level, the concentration of harmful chemicals goes up. These toxic chemicals reach the top of the food chain and ultimately affect humans as they are at the top of most food chains.

• In the case of human beings, chemicals that gather in their bodies may include arsenic and mercury. Moreover, pesticides such as polychlorinated biphenyls (PCBs) and DDT can also be part of the biomagnification process. These chemicals are carcinogenic in nature and hence are very dangerous for the health of all living beings.

Example of Biomagnification

Image 3: Biomagnification of toxins in a food chain: As the trophic level increases in a food chain, the amount of DDT concentration also increases. The X's represent the amount of toxic build up accumulating as the trophic level increases. Toxins build up in organism's tissues and fat.

• Marshes are often sprayed with DDT to control mosquitoes. The DDT gets mixed with water and accumulates in the cells of the aquatic organisms. Aquatic organisms do not selectively eat chemicals and cannot differentiate between the right and the wrong chemicals to eat.

• Clams and fishes that are up in the food chain eat these organisms. So, the DDT gets accumulated in their bodies now. Moreover, the concentration of DDT increases in the bodies of clams and fish. It has been found that the concentration of DDT in fish and clams is 10 times greater than the aquatic organisms.

• The concentration of DDT goes up as the food chain moves from one trophic level to another. For example, seagulls consuming fish gather more DDT in their bodies. It has been found that there has been an increase of 1000 times in the concentration of DDT in phytoplanktons than the concentration of DDT in water.

  Zooplanktons have 13 times higher concentrations than phytoplanktons, fishes have more than 40 times the concentration of DDT than zooplanktons, and sea-eating birds have 25 times more DDT than fish in their bodies. It is notable that DDT impacts the calcium metabolism of birds and is responsible for thinning of eggshells.

• In the 1940s and 1950s, DDT was used extensively to control mosquitoes and this led to a considerable decrease in the population of birds.

• Apart from DDT, mercury may also play a spoilsport in the case of predatory fishes. For example, the level of mercury present in the body of sharks, tuna, swordfish, etc. is more than that of smaller fishes.

Causes of Biomagnification

Agricultural Chemicals

The chemicals used for agriculture, such as pesticides, herbicides, fungicides, and fertilizers contain harmful chemicals that mix with soils. They can run off and mix with water in rivers. These chemicals end up meeting the oceans and there, they become the food for the fishes and other organisms. These harmful chemicals then find their way into human foods and accumulate in human bodies. In fact, these agricultural chemicals harm the entire food chain that consumes them.

Industries

Industrial waste released by factories may get mixed with rivers and water streams to find its way into oceans. These waste materials may contain mercury and arsenic apart from other harmful chemicals. These may be eaten by aquatic organisms and that way, they may enter the food chain.

Organic contaminants

Some organic compounds such as manures, and biosolids such as carbon, nitrogen, and phosphorus are important for plants. However, when they mix with water bodies, they may become a source of biomagnification, causing harm to the entire food chain of aquatic organisms to human beings.

Mining

Mining is responsible for extracting materials like cobalt, copper, zinc, and lead that may accidentally get mixed with water bodies and contaminate them. These substances are harmful to the health of living beings and when they get mixed with oceanic water, they are consumed by aquatic organisms. The levels of contaminants grow with each increasing trophic level.

Effects of Biomagnification

Effects on human health

Biomagnification affects human health in a significant manner. It has been observed that people who consume seafood regularly are diagnosed more with cancer than those who avoid seafood. One of the reasons for this is mercury that is accumulated in the body via biomagnification. Mercury is carcinogenic in nature.

Other effects

Other noted effects of biomagnification are found in the reproduction and development of all animals. As the poisonous elements grow in amount, they may affect the reproductive cycle as well as the processes of living beings. This may lead to the destruction of aquatic organisms, such as coral reefs and the entire food chain of animals.

Conclusion

Biomagnification is a growing threat to the health of human beings and other animals and we must be concerned with this for our own benefit. We must stop harmful chemicals from entering the oceans so that biomagnification can be avoided. This will need a strategic approach and we must take care to stop the mistakes that we have done in the past. Only then we can find a true solution for dealing with various health and wellness threats. Hence, it should be treated with the utmost care.

FAQs

Qns 1. What is biomagnification? How does it begin?

Ans. Biological magnification refers to the accumulation of non-essential and harmful chemicals in the body of living organisms at different levels of the food chain. The process of biomagnification starts when industrial, human, and agricultural waste is allowed to mix with oceans. It usually occurs when the waste materials find their way into the ocean via sewers, rivers, and water streams.

Qns 2. Give an example of biomagnification.

Ans. The use of DDT to control mosquitoes in marshes and thereafter the subsequent decrease in the population of many birds is a good example of biomagnification.

Qns 3. What is the element that is responsible for causing cancer from eating seafood?

Ans. Mercury is the leading cause of cancer from eating seafood.