| This thesis dealt with the tolerance value of benthic macro-invertebrate taxa, bio-assessment criteria in water quality using Biotic Index in China, and the establishment of benthic index of biotic integrity (B-IBI) in the health assessment of stream ecosystem. A comparison of the number of species, individuals and values of metrics between quantitative and semi-quantitative sampling methods were also studied.I A study on the comparison between quantitative and semi-quantitativesampling methods for stream macro-invertebrate assemblagesQuantitative sampling method for stream macro-invertebrates is well used in stream ecological study, and semi-quantitative method is widely used in water quality bio-assessment. The results from comparisons of the number of species, individuals and values of metrics between the two methods were showed as follows:1. In lotic water, there were no significant difference in number of species and individuals between quantitative (Surber net) and semi-quantitative (kick sampling) samples, although more species and individuals were collected by semi-quantitative than quantitative sampling. In lentic water, the significant difference was existed in the number of species ( z=-2.032, p<0.05), but it showed no significant difference in individuals between quantitative and semi-quantitative (D-frame net) samples.2. The average species similarity was 0.68 between semi-quantitative (kick sampling plus D-frame net sampling) and quantitative samples in the same site, higher than that of 0.56 in the lotic water, 0.45 in the lentic water.3. No significant difference was found in metrics calculated from the data of quantitative and semi-quantitative samples in the same site respectively.It is obvious that semi-quantitative was a scientific and practical method in water quality bio-assessment for macro-invertebrate assemblage sampling.II The calculation of the tolerance value of benthic macro-invertebrate taxa1. Ninety-two samples were obtained from mountain streams in Jixi, Ningguo, Xouning, Qimeng and Susong counties, Anhui province, and plain waterbodies in Qinghuaihe river and small water bodies in Zijingshan, Nanjing city, Jiangsu province from 1998-2002. 135 samples were referenced from published papers collected in Liaoning province(1998), Beijing(1982, 1991), Anhui( 1992) and Hunan provinces( 1981,1986).2. Using the calculation method of the tolerance value provided by Lenat(1993), eighty-one tolerance values of macro-invertebrate taxa were acquired. Among them, two genera in 2 families in Coleoptera, 2 genera inl family in Megaloptera, 14 genera in 7 families in Ephemeroptera, 2 genera in 2 families in Plecoptera, 6 genera in 5 familes in Trichoptera, 1 geneus and 3 families in Odonata, 12 genera and 3 sub-families in 3 families in Diptera, 5 species in 2 genera in Mollusca, 4 species in 1 genus in Annipula and others 1 geneus.3. Tentative tolerance values were given to 71 macro-invertebrate taxa based on the collection experience and reference data.III A study on water quality bio-assessment using Biotic Index (BI)1. Two methods were used to provide water quality ratings in bio-assessment using Biotic Index (BI), (1) Using the sampled sites meet the criteria for undisturbed and minimally impaired conditions, the confidence in the distribution of BI value for the 75th percentile to be used as the criterion dividing "unimpaired" form "impaired". Any values below the 75th percentile were considered as "excellent", and values above the 75th percentile, was quadrisected for different water quality ratings. (2)Using a sample of sites from the entire population, the 5th percentile of the BI from the population of sites was determined. Any values below the 5th percentile were considered as "excellent", and values above the 5th percentile, was quardisected for different water quality ratings. According to the method (1), Bio-assessment criteria of BI for stream was preliminary determined, <2.97, Excellent; 2.98-4.72, Good; 4.73-6.48, Good-fair; 6.
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