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Not all the macro invertebrates found in samples are listed on the biotic index scoring sheets. This is because some do not rely on oxygen within the water for survival. Many are able to collect air from the atmosphere and hold a bubble alongside their body to use like a scuba diver uses a tank of
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Then an identification key is used to help determine which category or group the organism belongs in and allows a numerical value be assigned to that organism. A worksheet is then used to calculate the final value or score of all the organisms found. Depending upon the worksheet's equations, the
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To assign a biotic index value to a specific water site, the tester first collects macro invertebrates from portions of the sample area of the stream, river or lake, and separates them into groups of similar-looking organisms. More extensive testing can be done by looking for certain microscopic
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Macro invertebrates limited mobility and extended presence in the water means that they are exposed on a continuous basis to water quality in that stream or river. In particular, many of these organisms breath dissolved oxygen that is in the water. They are also easier to see at the time of
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For those macro invertebrates that do rely on dissolved oxygen, some can only live in water that has a lot of oxygen. Others can live in water that doesn't have much oxygen dissolved in it at all. Generally, it is assumed that the more pollution there is in the water, the less oxygen.
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Some index worksheets combine groups 2 and 3 together, giving only 3 groups. Each group has a number assigned to it and is multiplied by the number of organisms found in that group. This is why identifying the type of organism is important.
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The biotic index works by assigning different levels of tolerance to pollution to the different types of organisms. The types of macro invertebrates and other organisms found during sampling are broken into 4 groups:
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Semi-Pollution tolerant: These organisms will be found in clean and slightly polluted waterways (Snails or Black Fly Larva)
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Pollution tolerant: These organisms will be found in polluted, as well as clean aquatic ecosystems (Leeches, Blood worms)
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Aquatic macro invertebrates have some general characteristics that make them very useful to assess stream health:
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Semi-Pollution intolerant: These organisms are sensitive to pollution (Dragonfly Larva or Craw fish)
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Pollution intolerant: These organisms are highly sensitive to pollution (Stonefly or
Alderfly Larva)
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in marine and freshwater ecosystems. Numerous biotic indices have been created to account for the
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present in a representative sample of the environment. It is often used to assess the
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found in each region of study. The concept of the biotic index was developed by
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They carry out part or all of their life cycle within the stream or river.
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William E. Sharpe, William G. Kimmel, and
Anthony R. Buda (2002).
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They are abundant and found in water bodies throughout the world
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in an effort to provide a simple measurement of stream
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score determines the condition of the water quality.
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44:and its effects on the biology of the stream.
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24:by indicating the types and abundances of
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207:Macroinvertebrate Community Index
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61:Usefulness of macro invertebrates
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197:Index of biological integrity
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119:Examples of Biotic Indices
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267:Environmental indices
257:Environmental science
221:"Biotic Index Guide."
127:Extended Biotic Index
228:"Stream Monitoring."
187:Biological integrity
138:Sludge Biotic Index
130:Family Biotic Index
233:2019-10-31 at the
141:Trent Biotic Index
202:Indicator species
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84:oxygen.
48:Technique
42:pollution
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231:Archived
146:See also
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