以底栖动物为指示物种对长江流域水生态进行评价

采用底栖动物作为指示物种对长江流域的水生态进行了调查研究和生态评价。在长江上游支流、中下游干流及沿江湖泊上选取36个代表性样点进行生态考察和底栖动物采样、鉴定和分析。采用Hilsenhoff生物指数和水化学分析对样点水质进行评价，对比分析了各样点底栖动物的结构组成及多样性。上游支流大部分样点水质清洁；中游干流及沿江湖泊水质受到轻度到中度污染；下游干流水质污染加重。底栖动物多样性在上游支流中最高，中游湖泊较高，干流中下游较低。总结得出了4种河床演变条件下的底栖动物群谱。上游支流河床稳定的河流底栖动物密度较大，物种丰富，多样性高；侵蚀下切的河流底栖动物密度、物种数和多样性较低；淤积抬升的河流底栖动物密度、物种数和多样性更低一些；河势散乱且河床运动剧烈的支流物种丰度和密度均很低甚至为零，生态条件差。

ECOLOGICAL ASSESSMENT OF THE YANGTZE RIVER ECO-SYSTEM WITH BENTHIC INVERTEBRATE AS INDICATOR SPECIES

The aquatic ecology of the Yangtze River Basin was investigated and evaluated by using benthic invertebrate as indicator species.Investigation and sampling of water and benthic invertebrates were conducted from 2005～2007 at 36 selected sites on the upstream tributaries，middle and downstream reaches and riparian lakes of the Yangtze River.The water quality of the sites was evaluated with Hilsenhoff biotic index and compared with the results of chemistry analysis.The results show that the water in the most upstream tributaries are of high quality，water in the middle reaches of the Yangtze River and riparian lakes are slightly and moderately polluted；and the water quality in the lower reaches is even lower.The individual density，taxa richness and biodiversity of benthic invertebrate are high at the upstream sites，moderate in the riparian lakes of middle reaches，and low at the sampling sites in the middle and downstream reaches.Fluvial process condition has a significant effect on the benthic assemblage structure.This paper concludes the pedigrees of the benthic fauna in four types of fluvial process conditions for the Yangtze River Basin.Stable streambed provides the best habitat for bio community and has the highest biodiversity.The bio community is stressed in incised channels and the biodiversity is lower.In the stream experiencing siltation the habitat is seriously impaired and the biodiversity is even lower.In the stream with strong bed load movement there is no benthic macroinvertebrate.