Biotic Index Fact Sheet
Introduction:
The aquatic environment can be affected by both natural and anthropogenic events. These may include the addition of synthetic substances to the water or some physical or chemical change that alters the hydrological regime.
Most organisms that live in a water-body are sensitive to environmental change, whether it is increased turbidity, chemical contamination or decreased dissolved oxygen caused by the introduction of sewage. These organisms may die, migrate, or they may reproduce or metabolize differently. What is important is to be able to identify these changes, through measuring and monitoring, in order to relate them water quality.
Note that in most cases, indices only work well for the water bodies in the regions in which they were developed, and may give anomalous results in other types of water body.
Biotic Indices
The basis of any aquatic eco-system is water and the quality of the ecosystem may be determined by the quality of the water. Biotic indices can give an indication of the quality of the water.
Biotic Indices, which are based on the presence or absence of particular indicator groups or species at the sampling point, are best suited for waters polluted with organic matter such as sewage. However, they have been recently developed for acidification of streams and lakes. Indices may be based upon the number of invertebrate fauna that are collected, identified and then counted.
Community Structure Indices
Each group is given a score, according to abundance, with the total score representing the index, and with the higher the score the cleaner the water.
Diversity indices attempt to combine the data on species abundance in a community into a single number. Stable eco-systems are characterized by a great diversity of species, most of which are represented by relatively few individuals. However, high numbers of individuals of only a few species may occur in instances where physical or chemical factors restrict habitat
The aquatic environment can be affected by both natural and anthropogenic events. These may include the addition of synthetic substances to the water or some physical or chemical change that alters the hydrological regime.
Most organisms that live in a water-body are sensitive to environmental change, whether it is increased turbidity, chemical contamination or decreased dissolved oxygen caused by the introduction of sewage. These organisms may die, migrate, or they may reproduce or metabolize differently. What is important is to be able to identify these changes, through measuring and monitoring, in order to relate them water quality.
Note that in most cases, indices only work well for the water bodies in the regions in which they were developed, and may give anomalous results in other types of water body.
Biotic Indices
The basis of any aquatic eco-system is water and the quality of the ecosystem may be determined by the quality of the water. Biotic indices can give an indication of the quality of the water.
Biotic Indices, which are based on the presence or absence of particular indicator groups or species at the sampling point, are best suited for waters polluted with organic matter such as sewage. However, they have been recently developed for acidification of streams and lakes. Indices may be based upon the number of invertebrate fauna that are collected, identified and then counted.
Community Structure Indices
Each group is given a score, according to abundance, with the total score representing the index, and with the higher the score the cleaner the water.
Diversity indices attempt to combine the data on species abundance in a community into a single number. Stable eco-systems are characterized by a great diversity of species, most of which are represented by relatively few individuals. However, high numbers of individuals of only a few species may occur in instances where physical or chemical factors restrict habitat
References: Chapman, D. (ed.) (1997) Water Quality Assessments: A guide to the use of biota, sediments and water in environmental monitoring. UNESCO/WHO/UNEP. Taylor & Francis, UK/USA. Stream Assessment : www.citeseerx.ist.edu Accessed 2012/06/03. Voshell, J.R., (2002) A Guide to Common Freshwater Invertebrates of North America. McDonald & Woodward. USA. Further Reading: Zimmerman, M.C. (1993). The Use of the Biotic Index as an Indication of Water Quality. Conference #5. ABLE. USA.