Aquatic Pollution and Coastal Management

Unit 11 : Monitoring and control of pollution

11.5.Biological Indicators of Pollution
Biological monitoring, or biomonitoring, is the use of biological responses to assess changes in the environment, generally changes due to anthropogenic causes. Biomonitoring programmes may be qualitative, semi-quantitative, or quantitative. Biomonitoring is a valuable assessment tool that is receiving increased importance in water quality monitoring programmes of all types.
There are two types of biomonitoring. One type of biomonitoring is surveillance before and after a project is complete or before and after a toxic substance enters the water. The other type of biomonitoring is to ensure compliance with regulations or guidelines or to ensure that the water quality is maintained.
Biomonitoring involves the use of indicators, indicator species or indicator communities. Generally benthic macroinvertebrates, fish, and/or algae are used. Certain aquatic plants have also been used as indicator species for pollutants including nutrient enrichment. There are advantages and disadvantages to each. Macroinvertebrates are most frequently used. Biochemical, genetic, morphological, and physiological changes in certain organisms have been noted as being related to particular environmental stressors and can be used as indicators.
The presence or absence of the indicator or of an indicator species or indicator community reflects environmental conditions. The absence of a species is not as meaningful as it might seem as there may be reasons, other than pollution, that result in its absence (e.g., predation, competition, or geographic barriers which prevented it from ever being at the site) . Absence of multiple species of different orders with similar tolerance levels that were present previously at the same site is more indicative of pollution than the absence of a single species. It is clearly necessary to know which species should be found at the site or in the system.