Biomagnigication meaning, process and effects

Biomagnification

In order to explain biomagnification the concept of bioaccumulation should be made clear first, as far as the term bioaccumulation is concerned it is the process whereby toxic chemicals or we can say pollutant accumulate in the target tissues of organisms. Bioaccumulation takes place when the rate of toxic chemicals exceeds the rate of its elimination. Bioaccumulation occurs within a trophic level. Now this will ease in understanding the concept of bio magnification.

The process of cumulative increase in the concentration of accumulated toxic substances at each successive trophic level is referred to as biomagnification. It is also known as bio amplification or biological magnification. Hence it is clear from the above two definitions that toxic substances which accumulate in organisms goes on increasing or magnifying along the trophic levels and reach to its maximum concentration at top level. Therefore, the term magnification is used.

Toxic chemical pollutants from diverse sources enter into food chains in a variety of ways, different organisms expose in different ways. Humans expose mainly through the food, water or air.

Features of toxic pollutants that show biomagnification

• They can’t be metabolized by the body.
• Their residence time in the environment is quite long that is they remain persistent in the environment and are commonly known as Persistent Organic Pollutants (POPs).
• Insoluble in water, instead they are fat soluble therefore can’t be eliminated from the body with urine  
• High mobility in the environment.
• Biologically active.

Common bio accumulating substances or pollutant

• Heavy metals such as mercury, cadmium, cobalt, lead, chromium, arsenic, copper, etc.
• Pesticides, herbicides, weedicides etc. such as
• Dichloro diphenyl trichloroethene (DDT)
• Polychlorinated biphenyl (PCB)
• Polychlorinated dibenzo-P-Dioxins (PCDD)
• Didenzofurans commonly known as Dioxins
• Organochlorine insecticides (OCPs) such as Aldrin, dieldrin and toxaphene

Process of biomagnification

The process of biomagnification was first of all bring into lime light by Rachel Carson in her influential book “Silent Spring” in the year 1962.

In order to explain this process let us take aquatic ecosystem into consideration, when toxic pollutants enter into a water body from different sources they are absorbed by the phytoplanktons .Suppose a phytoplankton absorb 1 ppm of toxin from its surrounding which are eaten up by zooplanktons say for example a single individual of zooplankton eat 10 contaminated phytoplanktons over a period of time, this zooplankton now have 10 ppm of toxin now in the next trophic level zooplanktons are consumed by small fishes for instance a single fish consume 10 zooplanktons over a period of time, this small fish now nave 100 ppm of toxin in the body. Similarly, in the next trophic level say for example an individual human consumes 10 fishes over a period of time, this individual human now has 1000 ppm of toxins in tissues in this way concentration of toxins goes on increasing or magnify. It is also clear from the above that the constituents of topmost trophic level have greater concentration of accumulated toxins.

       

Effects of biomagnification

Biomagnification of toxic chemicals not only effect the human health but health of aquatic organisms is also effected to a great extent. The effect of biomagnification on keystone species is a matter of concern because it effects all other organisms.

Effects on human health:

Besides terrestrial food humans also depend on seafood like fishes, prawn, Nelumbo nucifera, Trapa natans etc. on consuming the toxic substances accumulated in them pass on to humans since humans consume a good amount of fish meat the accumulated toxins magnify inside target tissues of humans and cause serious health issues such as

• Cancer,
• nervous system disorder,
• skin infection,
• kidney diseases,
• respiratory problems,
• endocrine disruption,
• heart ailments,
• hepatomegaly,
• Parkinson’s disease,
• muscular dystrophy,
• Alzheimer’s disease,
• genotoxicity,
• birth defects,
• Sometimes even death can occur if seafood is too much contaminated with heavy metals especially mercury.

Impact on fauna:

The accumulation of toxic pollutants poses a great threat to aquatic as well as terrestrial fauna. Sea birds are the most effected as compared to all other organisms, even small doses show significant adverse effects in faunal population. Some common effects are

• Interruption in egg production because the accumulated toxins especially heavy metals and DDT hinder the complete formation of egg shells. Which result in their easy breakdown.
• Reduced growth.
• Immune dysfunction due to bioaccumulation is one of the leading cause of increased mortality rate among marine mammals.
• Thyroid deficiency is seen in seals due to consumption of contaminated fishes.
• Reproductive system of the aquatic fauna is also effected.
• Epidermal lesion.
• Accumulation of toxic substances in coral reefs result in death and decay of such a precious resource.
• In fishes accumulation of different heavy metals cause swollen of gills, reduced locomotion, damage reduced egg production, hypocalcemia , depletion of lymphocytes.reduction of viable spermatozoa, larval deformities and mortality.