Let me simplify this for you. Biomagnification is a cumulative increase in the concentrations of a persistent substance (e.g. pesticides, metals, etc.) as it moves up the food chain. This occurs when agricultural, industrial, or human waste pours into the ocean directly or via rivers, sewage, etc. Some of the most dangerous of these toxins settle in the sediment of the sea floor and are consumed by bottom feeders.
With each step up the food chain, there is an increase in the concentration of these chemicals. This affects humans because a large percentage of the fish we consume are higher on the food chain and therefore likely to carry a high concentration of potentially harmful chemicals.
The contaminants include heavy metals namely mercury, arsenic, pesticides such as DDT, and polychlorinated biphenyls (PCBs) compounds, which are then taken up by organisms because of the food they consume or the intoxication of their environment.
Process of Biomagnification
Here is an explanation showing the process of biomagnification:
Release of toxic chemicals and pollutants into the environment
The entire process starts with the release of toxic chemicals and pollutants into the environment, which eventually work their way into soils, rivers or lakes, and the seas. The concentration of these toxic chemicals and pollutants seem to be very low when released in different environments. They are very minute even in terms of weight.
Phytoplankton are small plants that float in the seas that normally absorb these toxins. Once absorbed, the toxins stay in their tissues without being excreted or broken down. With time, the toxins accumulate to high concentrations (up to 200 parts a trillion), which represents a toxin accumulation increase by about four-fold.
Zooplankton refers to small marine animals that float in the seas. They consume the phytoplankton and thus take in the toxins, which stay locked in the organism’s tissue without being excreted or broken down. Over time, the toxin concentration increases up to two parts per billion, which represents about a ten-fold increase in the previous concentration.
Small fish consume the zooplankton
Whenever the small fish feed on the zooplanktons, they take up the toxins, which get absorbed in their fatty tissues. As a result, accumulation occurs and the concentrations build up to about 20 parts per billion, which is another ten-fold increase.
Large fish graze on the smaller fish
Again, when the large fish graze on the smaller fish for food, they consume the toxins that accumulate in their fatty tissues. The concentrations become higher up to ranges of 80 to 100 parts per billion. This is about four to five-fold increase in the toxic levels.
The top food chain organisms consume the fish
The organisms at the top of the food chain including the marine mammals such as dolphin, sea birds, and humans gradually build up the toxins in their tissues such as their liver when they consume the large fish. The levels of concentrations here increase to the highest ranges of 10,000 to 15,000 parts per billion. The results impact the animal’s fertility and make them vulnerable to diseases as they interfere with the normal functioning of vital organs.
Effects of Biomagnification
Humans become more susceptible to cancers, liver and kidney failure, respiratory disorders, birth defects in pregnant women, brain damage, and heart diseases are a result of mercury, cadmium, lead, cobalt, chromium and other chemical poisonings. For instance, diseases like hepatitis and cancer have been attributed to consuming seafood that has been poisoned by mercury and polycyclic aromatic hydrocarbons (PAHs).
The various toxic elements get accumulated in the vital organs of the various aquatic creatures, thus affecting their reproduction and development. Selenium and heavy metals such as mercury also affect the reproduction of aquatic creatures such as fish as it destroys their reproductive organs. Besides, PCBs (polychlorinated biphenyls) also biomagnify and impair reproduction and are considerably high in aquatic systems.
The coral reefs are destroyed by cyanide, which is used in leaching gold and in fishing. The reefs provide for spawning, feeding, and dwelling grounds for numerous sea creatures. When destroyed, the survival of aquatic creatures is highly compromised.
Many sea creatures depend on the natural food chain for survival. When chemicals and other toxins are carried into the soils, rivers, lakes or oceans and taken up by various organisms, it disrupts the interconnected relationships within the food chain. The creatures or plants intoxicated with substances such as mercury, copper, chromium, selenium and cobalt may also be consumed by humans and top animals in the food chain leading to susceptibility to diseases, reproductive disorders, and even deaths. Biomagnification affects humans THE MOST because we are at the top of the food chain, thus the accumulated toxins and chemicals are in their largest concentration amongst us.
Interesting, right? Did you think what you ate mattered so much? It does, though. So, your eating habits are very crucial, especially during exam preparations
Keep this in mind the next time you wonder about biomagnification. 🙂
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