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Sunday, April 1, 2012


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By visual observation, we most often remain unable to detect pollution in our natural resources. So, we go for laboratory tests to estimate the real extent of pollution. However, pollution can be assessed sometimes through visual observations too, and in that case we look for some bioindicators expected to remain present in the natural resource, if it has been polluted by some pollutant. Observation based on knowledge of bio-indicators is one of the quickest and effective ways of judging pollution through visual observation.

Lichen on tree trunk 

Lichen on rock 

A bioindicator is a living organism that gives us an idea of the health of an ecosystem . Some organisms are very sensitive to pollution in their environment, so if pollutants are present, the organism may change its morphology, physiology or behaviour, or it could even die. 

In other words, living organisms that show the status of environmental quality through their sensitivity are called as bio- indicators. The bioindicators are very useful in finding out pollution because they help in identification of the type of pollution. Let us take a few examples-
(i)  The presence of Coli form bacteria indicates water pollution due to fecal matter.
(ii)Movement of Catla and Labeo (Rohu) fish species away from their habitat shoes pollution of water due to industrial waste. Similarly, the death of Amphibians and fish in pond water shows Eutrophication.

(iii) Abundance of diatoms and Eichornia in water indicate pollution due to mixing of sewage in water.
(iv)  Growth of some algal species like Chara shows water pollution by organic and industrial wastes.          
(v).Microorganisms can also be used as indicators of toxins in an ecosystem. Some microorganisms will produce stress proteins if exposed to certain pollutants. By measuring the levels of stress proteins, we can get an idea of the level of pollution present in the environment.
(vi). Lichens that live on surfaces of trees, rocks or soil are very sensitive to toxins in the air. They are so because they obtain their nutrients mostly from the air. If we see too much of lichens growing on the stems of forest trees, one can say that the air inside the forest is clean. However, different species of lichens have different levels of susceptibility to air pollution, so we can get an idea of the pollution level by observing which species are present.
(vii).If toxins are present, certain plants may not be able to grow in the area affected.
(viii).Monitoring population numbers of animals may indicate damage to the ecosystem in which they live.
(ix).Algal blooms are often used to indicate large increases of nitrates and phosphates in lakes and rivers. 
Key Words : Indicator,environmental quality, Phosphate, toxins

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