ABSTRACT
Natural events and anthropogenic influences can affect the aquatic environment in many ways: synthetic substances may be added to the water, the hydrological regime may be altered or the physical/chemical nature of the water may be changed. This chapter explores the basic principles behind the biological methods that have been developed for local use and are based on specific species. The flora and fauna present in specific aquatic systems are a function of the combined effects of various hydrological, physical and chemical factors. In addition to natural features, biological communities are often affected directly by human activities or indirectly by processes influenced by anthropogenic activities. The use of biota provides an integrated measure of all impacts on a water body as well as a possible historical interpretation of past pollution levels. Biological methods are suitable for all three levels of monitoring: simple, intermediate and advanced, and their use is recommended in conjunction with chemical and hydrological monitoring and assessment programmes.
