Biological Magnification: If you are a student of Biology or other related natural science courses, you may have studied or heard about the field called “ecotoxicology“. This field of biology focuses on the negative effects of harmful chemicals and toxins on different ecosystems and the living organisms present there.
Aside from that, it also takes into account the direct and indirect effects of these chemicals on the overall structure of habitats as well as the amount of food in that area.
In this article, we will give you a brief overview of how ecotoxicology works. Here, you will learn about how these harmful chemicals make their way through soils, different bodies of water and in biological food chains in the process called biological magnification.
Table of Contents
- Definition of Biological Magnification
- Examples of Biological Magnification
- Causes of Biological Magnification
- Effects of Biological Magnification
Definition of Biological Magnification
Also referred to as “biomagnification” or “bioamplification,” biological magnification happens when there is an increase in the number of chemicals and toxins that accumulate through the trophic levels of a food chain. Chemical substances from agriculture and industries tend to be released into the environment, making their way toward food chains and food webs.
Normally within food chains and food webs, biological magnification doesn’t directly affect living organisms. However, exposure to these harmful chemicals may cause some long-term and irreversible side effects.
- Often, biological magnification is confused with the term bioaccumulation. However, it is important to note that the two are significantly distinct from one another. The latter refers to the phenomenon wherein toxic chemicals accumulate or gather inside the cells and tissues of living organisms. On the other hand, it is good to know that these two processes are interconnected in a way. When living organisms can no longer dissolve the chemicals present in the food chain, they tend to accumulate them inside their bodies, thus resulting to bioaccumulation.
- As you move up the food chain, the vulnerability to biological magnification and bioaccumulation also increases. Hence, organisms located in the highest levels of the food chain (usually tertiary consumers) also have the highest possibilities of accumulating most chemicals.
- This phenomenon of increasing substance concentration as you move higher in the food chain is called as the food chain energetics.
Examples of Biological Magnification
Here is an example of biological magnification:
- For crops and plants (producers), to eradicate the pests, pesticides, and fertilizers are being used. When animals (herbivores) such as deer, goats, & cows graze these plants, the toxic substances get into these animal systems.
- When the primary consumers such as foxes/wolves hunt these herbivores for food, the toxic materials get into wolves systems.
- The carnivores (apex of the food chain) such as tigers consume these wolves, the toxic substances get into tigers system.
- Now if we compare plants and tigers on the toxicity level, the accumulation of toxic substances would be higher on tigers than of plants because tigers eat many wolves who eat many deer who eat a lot of plants with pesticides on them). So the toxic level has magnified to a different degree, hence the name – biological magnification.
Causes of Biological Magnification
Biological magnification, despite being a biological phenomenon, is often caused and triggered by anthropogenic factors. Some of these causes include organic contaminants, agricultural and industrial wastes, pollution from plastics, and heavy metals from mining.
1. Organic Contaminants
Organic contaminants like carbon, nitrogen, and phosphorus are known to be very abundant in the natural environment. As a general rule, too much of everything can be very bad. While these chemicals are known to be necessary for organism survival, their excessive amounts in ecosystems can lead to a phenomenon called eutrophication.
- As a result, living organisms like prokaryotes and algae exhibit rapid and exponential growth. Because of their excessive population, other organisms die as a result of oxygen depletion.
2. Agricultural and Industrial Wastes
Chemicals from inorganic fertilizers, herbicides, pesticides, and fungicides are often known to contaminate soils and bodies of water via runoff from rains and storms.
- Aside from that, industrial wastes from factories and other industrial operations can also contribute to the release of toxic chemicals and heavy metals to the food chain.
In the recent years, pollution of oceans due to excessive plastic disposal has become a significant global environmental problem.
- For instance, a substance present in plastics, called as Bisphenol A, is considered as one of the leading chemicals that pollute the environment.
Last but not the least, are mining activities that result in the discharge of heavy metal deposits (i.e., zinc, silver, gold, cobalt) into aquatic environments. As a result, levels of chemical toxicity in these areas increases tremendously.
- Aside from polluting aquatic plants, metal pollution of water can also contaminate drinking water systems. Disturbingly, metal contamination is considered to be very hard to treat.
Effects of Biological Magnification
As alluded to earlier, biological magnification, especially when not controlled, can be fatal to living organisms. The following are just some of its negative effects.
1. Pollutant Build Up
Pollutant build up, especially from those persistent chemical elements, is one of the most common effects of biological magnification. Being made up of a single element, these chemicals accumulate fast, and when they do, they become very hard to biodegrade. Water plants and algae can easily accumulate harmful chemicals because they share similar qualities with the kinds of nutrients these organisms need for growth.
- If by any chance the chemical is still present within the plant after being eaten by a larger organism (in the food chain), the next organism will get to absorb that chemical as well. And as it continues to consume more of those plants, the chances that the larger organism absorbs more chemicals will also increase.
- One of the most common examples of biomagnification is algal bloom that often leads to red tide. In this case, excessive amounts of chemicals (presumed by the organism as a nutrient) cause the overgrowth of the alga known as Karenia brevis. This alga, which is color red due to the pigment xanthophyll, is capable of producing a certain kind of neurotoxin that can be deadly to organisms that consume them. Symptoms of poisoning from red tide include numbness and digestive problems.
2. Bioaccumulation in Fat Cells
While some toxins are easily removed from the body, there are also those foreign chemical substances that tend to be stored within the fat cells of organisms. Such occurrence is very hard to treat because some of these chemicals can only be removed using specific enzymes.
- If the organism is lucky enough, it may have the capability to produce enzymes that can degrade such chemical. However, if otherwise, the chemical substance may gradually accumulate inside its fat cells and become irrecoverable.
3. Effects on The Health of Organisms
As alluded to earlier, organisms located at the higher level of the food chain also harbor the higher risks for biomagnification. Nevertheless, the mere build-up of these harmful chemicals inside living cells and tissues can pose a great risk to health.
- Mercury, for instance, is a toxic chemical that affects the central and peripheral nervous system as well as cardiovascular system. Because of this, the ingestion of mercury can cause a wide variety of diseases, reproductive problems, mutations, birth abnormalities, behavioral changes, and death.
- Alarmingly, toxic chemicals like mercury tend to settle on the ocean floor and are taken up by organisms that feed on plants and sediments.
Environmental problems like biological magnification have already been present for a long time. As you have seen in this article, humans are the biggest threat to the ecosystem, and ironically, we are also the ones who can take actions to prevent its destruction. Knowledge and awareness are the first steps to doing this.
Timely concerns about environmental sustainability intensify the need to teach people about the relationship between human health and the states of our ecosystems. By engaging in activities, we develop a greater understanding of the core values between humans and environment.
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