Ecological Impacts Of Water And Sediment Transportation On Macroinvertebrate Community In Rivers

The ecological impacts of water and sediment transportation on macroinvertebrate communities in rivers are studied through field investigations and experiments. Macroinvertebrates are used as indicator species in the assessment of river ecology. Macroinvertebrate samples were taken from 64 sampling sites on 32 rivers in China. Various species of macroinvertebrates were identified from the samples and they were compared and analyzed for the effects of substrate, fluvial process, and water pollution. Three field experiments were conducted to study the effects of substrata replacement with sediment of different sizes, the effects of aquatic habitat fragmentation by isolating riparian waters from the river, and the relation between the number of species in the samples and the sampling area.Biodiversity of macroinvertebrates varies with grain size of substrata, and different benthic organisms dominate in different types of substrata. Cobble substrate has the highest biodiversity, and sand substrate has the lowest biodiversity. The macroinvertebrate assemblage is also significantly affected by the stability, porosity, and interstitial dimension of the substrata, while it is rarely affected by the shape and the surface roughness of the sediment particles. Aquatic plants are favorable for macroinvertebrate assemblages. The effect of streambed substrate on macroinvertebrates is well understood, integrating both the results of the field investigations and the experiment.Water pollution results in a decrease of macroinvertebrate biodiversity and disappearance of intolerant species. Shredder, scraper and predator reduce following the increase in the concentration of total nitrogen. Collector-gatherer increases with the increased nitrogen. Because the macroinvertebrate communities are affected by pollution, water quality may be assessed by using macroinvertebrates as indicators. The results show that water quality assessment using macroinvertebrates as an indicator agrees with water chemistry analysis.The effect of fluvial process on the distribution of macroinvertebrates is studied. The rivers, according to their fluvial conditions, are classified as streams with a stable channel bed, degrading or aggrading channel beds, or intensive bed load motion. The compositions of macroinvertebrate fauna for the four types of rivers are very different. Stable streambeds provide the best habitat for benthic communities and have the highest biodiversity. Benthic communities are stressed in incised channels and the biodiversity is lower. In streams undergoing siltation habitats are seriously impaired and the biodiversity is even lower. In streams with strong bed load movement there are hardly any macroinvertebrates colonizing. This dissertation also presents the pedigrees of the benthic fauna in the four types of rivers.The taxa richness, density and biodiversity of macroinvertebrates greatly decrease in the isolated plots due to the habitat fragmentation. The smaller the isolated habitat plot, the more the biodiversity decreases. Habitat fragmentation also results in a succession of macroinvertebrate communities. A Habitat Suitability Index for macroinvertebrates (HSIm) is proposed in this dissertation, integrating the effects of the primary physical (including biotic and abiotic) and chemical conditions. The biodiversity index value and taxa richness increase non-linearly with the HSIm.Moreover, ecological restoration strategies for the impaired reaches of the East River basin are suggested in the dissertation. Macroinvertebrates distribution in the Yangtze River basin is studied.