Invertabrate Community Index(ICI)

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Invertebrate Community Index(ICI)-The following is from a paper by Dr. Steve Gordon of the Ohio State University. For the entire paper please click here.

Similar to IBI for fish, ICI is a summary measure of 10 metrics representing aquatic macroinvertebrate community integrity and is evaluated and scored in relation to conditions at relatively undisturbed reference sites (Ohio EPA 1989). In this index, a site can receive a 6, 4, 2 or 0 score depending on how it compares to the specified reference site. Scoring is very similar to IBI; here the maximum score is 60 (10x6) and the minimum is 0 (0). Ohio EPA decided to use both fish and macroinvertebrate indices because there is a large amount of information on life history, tolerances and distribution and both groups have been widely used in similar biological assessments (Ohio EPA 1987). The following is a brief description of the metrics comprising Ohio EPA's ICI as outlined by Ohio EPA (1987).

Total Number of Taxa - species richness and diversity increases with warm water stream quality; inverse relationship with drainage area

Number of Mayfly Taxa - pollution sensitive species; greater proportion of taxa indicates higher environmental quality

Number of Caddisfly Taxa - main component in larger, unimpacted waterways; wide range of pollution tolerances within taxa

Number of Dipteran Taxa - have wide range of tolerances to pollution; often only organism collected under heavily polluted conditions - greater proportion suggests lower stream quality

Percent Mayfly Composition - easily affected by even minor disturbances; serves as measure of overall levels of stress and disturbance

Percent Caddisfly Distribution - quickly absent under environmental stress; serves as a measure of stream stress

Percent Tribe Tanytarsini Midge Composition - often predominant group at minimally impacted sites; pollution tolerances are intermediate

Percent Other Dipteran and Non-insect Composition - includes non-insect invertebrates such as worms, isopods, snails, etc.; main community component in poor water quality conditions - greater abundance indicates lower environmental quality

Percent Tolerant Organisms - tolerant to toxic and organic pollution; greater proportion of organisms indicates lower overall environmental quality

Number of Qualitative EPT Taxa - qualitative measure of habitat diversity and water quality; measures richness of mayfly (Ephemeroptera), stonefly (Plecoptera) and caddisfly (Trichoptera) taxa


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Last updated: April 7, 2009.