URIhttp://vishub.org/pictures/649BISEL in HungaryThe Biotic Index
The Biotic Index (BI) is a biological water quality assessment method for water courses. It is a simple method that permits one to gain a clear insight into the ecological quality of water courses with very limited means. Biological water quality assessment is a valuable supplement to chemical water quality assessment systems, scientifically as well as educationally.
The Belgian variant (Belgian Biotic Index, BBI) was set and repeatedly tested by a cooperation of several laboratories. Since 1984 it is the offical standard method for biological water quality assessment in Belgium. This BBI has proven to be much more applicable, with slight adaptations, than merely in Belgium, at least all over Europe.
Concerning application at the secondary education level the BBI has one big advantage compared to other methods (standardized elsewhere in Europe): the assessment of the biotic index is quick, easy and requires no work for a specialist or big investments.
In the educational field the BI integrates in an active way (field work) the biology lessons of classifications and ecology: the determination of the macro invertebrates is based on the principles of the biological classification system and its interpretation in terms of water quality is connected with human influences on the environment. When the assessment of the biotic index is combined with chemical water analyses, clear conclusions can (mostly) be drawn concerning the cause of the pollution and thus we have an integration of the biology and chemistry lessons.
Principles:
1. Changes in river quality induce in the flora and fauna to a degree dependent upon the degree of change in water quality. The macro invertebrates (invertebrate animals visible with the naked eye) serve as "bioindicators" for water quality.
2. The more sensitive organisms can only live in water of a high degree of cleanliness.
3. The cleaner the water, the more various species can live in it.
Method:
1. Sampling: try to catch as many various species of water organisms as possible.
2. Sample processing: identify and enumerate them.
3. Interpretation: classify them according to their sensibility to water pollution and express your results as a score for the biological water quality.
Advantages:
1 A major advantage is that the biological water quality can be expressed as an index or a score and be visualized by means of color codes.
2. Biological assessment unlike chemical assessment, have the advantage to integrate the water quality over a longer period of time and thus better reflect the general ecological condition of a water course.
3. Biological communities respond to a wide range of a pollutant. In this respect, the BI reflects the general biological condition of a water course, too.
Limitations:
1. Biological surveillance will detect ecological changes indicative of water quality change; it doesn't identify the specific cause of the change, which has to be identified by chemical analyses.
2. It may be necessary to carry out the biological testing several times a year to account for seasonal variations.
3. Although biological surveillance will detect ecological change a weakness in the system is interpreting these ecological changes in terms of water quality. Consequently a proliferation of methods occurs. Almost all countries use their own index.
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