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close this bookStudying Water Pollution through Fish Assessment (Indian Institute of Sciences)
View the documentAcknowledgement
View the documentAbstract
View the documentIntroduction
View the documentLakes and Bangalore City
View the documentLiterature review
View the documentMeans of Detecting Water Pollution
View the documentGeneral review of assessment procedures
View the documentRemote Sensing
View the documentMethods
View the documentResults and Discussion
View the documentReferences

General review of assessment procedures

It would go beyond the scope of this paper to present here an exhaustive discussion of all possibilities which are available for the use of bioindicators and biomonitors in aquatic ecosystems. Therefore for classification of water pollution we review the following methods.
To begin with, however, a brief review of the different types of evaluative procedures is in order. These are:

1. Physical and chemical water analysis

2. Biological procedures based on the use of:
a) Bioindicators,
b) Biomonitors

3. Remote sensing

Physical and Chemical Water Analysis

With the aid of physical and chemical analysis techniques, it is possible to obtain information on the condition of water at the place and time at which the samples are taken. Depending on the quality of the investigatory methods used and the number of parameters studied, some useful data are yielded on the quality of the water at that point in time. How accurate and detailed the results must depend upon the purposes for which analyses are performed. In order to obtain more precise data, repeated analyses are necessary; these can even be aimed at identifying changes during the course of a single day [8]. A number of parameters are measured, including the presence of the amount of organic carbon, ammonium, nitrate, orthophosphate and oxygen, as well as the biochemical oxygen demand (BOD). By means of additional tests, it is also possible to obtain additional information on the concentration of toxic substances. As is to be expected, continuous taking of samples and performance of analyses are associated with high technical, financial and labour inputs. The costs incurred grow with the number of samples taken and the range of substances which are tested for. Even the industrialized countries can only afford to do this within certain limits. Nevertheless, within the scope of major technical projects, it would be useful to carry out similar sample-taking and analysis programs at various locations for monitoring purposes. This would have to be specifically decided upon with respect to each individual case [6,7,8,9].

When evaluating water pollution with the aid of bioindicators, an understanding of an organism's reaction to changes in its environment is essential. These reactions can take the form of growth and/or increased population density, modified activity, reduced growth, a decline in population, or even death. Depending on their degree of complexity, size, generation time and other factors, organisms and different species react at varying rates. Most bacteria adapt very quickly to environmental changes. Protozoa and algae take longer, and insects - many of which live for a year or longer as larvae in the same aquatic environment - require longer periods to react to changes in their surroundings. As a rule, organisms with longer generation times respond more quickly to negative changes -if they exceed the limits of what is tolerable - for example by migrating to zones with satisfactory living conditions or by dying. Depending upon the time which bioindicators or indicator organisms spend in a body of water, they are subjected to the prevailing environmental conditions and any changes that occur. Thus, members of a related group of organisms or a biological community integrate and reflect environmental conditions and possible changes over an extended period of time. Consequently, critical evaluation of the species compositions of a biocoenosis can yield sufficient data on the situation of a body of water and the range of fluctuations in the environment over a lengthy period of time.