| The River Continuum Concept (RCC) is a generalized conceptual framework for characterization of pristine running water ecosystems. RCC asserts that streams are continua of both geomorphologic and biological factors. Macroinvertebrate community structure in natural systems will be structured so as to promote the most efficient energy utilization and the most efficient use of resources. Changes in community structure and function changes are a function of changes in geomorphic, physical and biotic variables. In North America and Europe, the River Continuum Concept is used as an analytical template for conducting assessments in a river ecosystem. But in our country the reports related to the RCC research is very scarce. The objective of this research is to test the RCC from] st to 6th order streams of Changjiang River watershed in southern mountain area of Anhui Province, to explore the function and structure of Macroinvertebrate community succession rule of the river. The Changjiang River water quality assessment is carry on by comparison of the community characters of the point - pollution or non-point pollution sites to the hypothesized RCC, the Macroinvertebrate Community Structure Indices and BI index were used in the assessment.The study shows that the substrate and other physical variables (stream mean width, depth and velocity) in Changjiang River system from 1st to 6th order streams present a continuous gradient of physical conditions. Accordingly, the change trend of each functional feeding groups from 1st to 6th order streams is congruent with RCC, but the degree of the gradient changes of shredder, collector and scraper groups are much smaller than those predicted by the theory because of the influence of non-point pollution.Physical-chemical data shows that slight-moderate point pollution exists in Changjiang River. The inorganic pollution exists at the testing site of the 1st stream, and the predator's number at the testing site is obviously smaller than that of the reference site,while the number of shredder, collector and scraper each at the testing site is close to the number of those at reference site respectively. The organic pollution exists at the testing site of the 3rd stream, and the collector's number at the testing site is obviously higher than that of the reference site, however, the scraper's number at the testing site is smaller than that of the reference site. Finally, the testing sites are dominated by pollution tolerance species while the reference sites are dominated by pollution intolerance species.The benthic macroinvertebrate dominant concentration gradually increases from 1 st to 6th order streams. The change trend of EPT Taxa Richness and Total Taxa Richness resembles to the change trend of Shannon-Wiener Diversity Index, and there is highest macroinvertebrate diversity in 4th order stream among 1st to 6th order streams in Changjiang River.Tentative ratings criteria of Similarity Index (SI) and Total Taxa Species (TTS) for water bio-assessment are provided, according to the benthic macroinvertebrate distribution from 1 st-6th order streams and the physical-chemical parameter assessment. SI criteria: >0,6, no impact; 0.4-0.59, slight impact; 0.2-0.39, moderate impact; 0-0.19, severe impact. TTR criteria: >30, non-pollution; 20-29, slight pollution; 10-19, moderate pollution; 0-9, severe pollution. These Tentative ratings criteria can be applied in southern mountain area of Anhui Province.Biotic Index, EPT Taxa Richness, Total Taxa Species and Similarity Index are sensitive to point pollution. Shannon-Wiener Index is blunt to moderate and slight organic pollution because it can't reflect the tolerance pollution species shifting. Among the bio-assessment metrics, we confirm that BI is one of the most effective metrics (using rating criteria and TV by Wang Beixin, 2003), which is generally consistent to TTS and SI, and much sensitive to slight-moderate organic pollution.The Trichoptera adult community structure of the river from 1st to 6th...
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