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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Wetlands II
DEVELOPMENT AND EVALUATION OF DIATOM-BASED BIOTIC INDICES FOR MAINE WETLANDS.
Y.K. Wang and R.J. Stevenson. Department of Zoology, Michigan State University, East Lansing, MI 48824, USA
The development of biotic indices was based on the experiences and knowledge of field biologists, such as Hilsenhoff biotic index and Bahls diatom pollution index. We tried to use numerical approach to develop biotic indices and evaluate their performance. Three types of biotic indices were developed. First two indices were based on weighted average approach. First index (W1) assigned species into categories of an environmental variable according to their environmental optima. Second index (W2) weighted species sensitivity in index calculation. The third index (I1) used indicator species analysis to assign the probability of species in each category. Indices were developed for conductivity, alkalinity, pH, and TP, and were evaluated by correlation with site total disturbance rank and relevant water chemistry from test data set. The performance of biotic indices varied depending on the evaluation criteria. Simple weighted average approach had the highest average correlation with relevant water chemistry, W2 second, and I1 the last. I1 had the highest average correlation with total disturbance rank, W1 second, simple weighted average last, but no statistically significant difference. The level of the relevant environmental variable inferred from calculated values of a biotic index is usually lower than the real level.
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