If nothing is known about the environment, repeated surveys are required before commencing a full-fledged biological monitoring. The first survey is typically considered baseline survey, which is followed by a more detailed survey. In view of later survey, final decisions are made with respect to methods, species, and site for monitoring. Monitoring study typically includes a control site, a suitable area that has remained relatively unim-pacted. For example, if one wants to study the effects of effluents from a particular industry, an area farther from discharge of effluents will be used as control. In this case, some effects will be common to both the study area and the control, for example, climatic changes, whereas others will be due to discharge of effluents observed only in the study area.
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