Studies On Ecology Of Benthic Macroinvertebrates In East River Basin

East River is an important tributary of the Pearl River. It provides drinking waterfor more than40million residents in Hong Kong, Guangzhou, Shenzhen, and otherbig cities, and has respect to the economic development and long-term stability ofHong Kong and the Pearl River Delta region. Systematical investigations of benthicmacroinvertebrates assemblages were carried out in Guanlan River Basin and XizhiRiver Basin. The two rivers are tributaries with different river patterns of the EastRiver. And ecology of macroinvertebrates community in the East River Basin wasstudied. Major conducted studies are as follows: the relations between stream orderand different groups of macroinvertebrates were studied; the pollution level withrelation to the biodiversity of macroinvertebrates assemblages were studied; ecologyassessment of Xizhi River Basin and Guanlan River Basin based onmacroinvertebrates communities were carried out; a preliminary system of ecologyassessment was established; strategies of river ecological restoration for ecologicalproblems in East River Basin were proposed. The main results are as follows:1. By the investigations of macroinvertebrates assemblages in24sampling sitesin East River Basin, a total of99genus were identified, belonging to8classes and67families. In Xizhi River, biodiversity was relatively high. Mayflies and caddisflieswere dominant groups, especially the Baetidae family. In comparison, in GuanlanRiver Basin, biodiversity was low, taxa richness of8sites ranged from0to5,pollution-tolerance tubificids were dominant groups. There was nomacroinvertebrates in two sites of Guanlan River, where the concentrations of totalnitrogen and total phosphates were about38plus milligram per liter and3plusmilligram per liter, respectively.2. The results indicated that the water quality is a significant factor whichinfluences the distribution of macroinvertebrates communities. It is an overall inversecorrelation between the pollution resistibility of the communities, which reflects thepollution level of the water body, and biodiversity. As for macroinvertebratesassemblages, pollution level is a limited condition, which decides the threshold andsensitivity of biodiversity. On condition that the water is clean or slightly polluted, biodiversity has a wide variation range. However, biodiversity retains in quite a lowlevel when the water is heavy polluted.3. A preliminary system and relevant criterion of ecology assessment in EastRiver Basin was established. Based on graph of the correlation between biodiversityand water quality,9ecology patterns were classified by4thresholds. Each ecologypattern shows a basic ecological regime and a fundamental principle for ecologicalrestoration. The ecology assessment system is completely on the basis ofmacroinvertebrates communities. The two parameters were Biotic Index andShannon-Wiener biodiversity index. The preliminary system can be used for largescale investigation of macroinvertebrates and quick ecology assessment.4. Xizhi River system was divided into5stream orders. In Xizhi River Basin,collector-gathers were the main functional feeding groups. With the augment ofstream order, collectors increased in upper reaches and decreased in lower reaches.The variation range of the collector-gathers was higher than that of thecollector-filters. Scrapers sharply increased in fourth-order rivers, and predatorsreached its maximum in second-order streams. The average abundance of shredderskept less than fifty individuals per square meters. The main life habit groups ofmacroinvertebrates in Xizhi River Basin were swimmers and clingers. Taxa richnessof clingers was quite high in upper reaches and decreased to a low level in middle andlower reaches. Burrowers and climbers reached their maximum in third-order rivers.Totally, the composition of the functional feeding groups and the life habit groupsconformed to the river continuum concept, though reasonable discrepancy with theconcept existed.5. Based on the fact that ecosystem of the East River was affected by pollution,unreasonable sand mining, dam construction and operation, and artificial channelwith low habitat diversity, main methods for ecology restoration were presented. First,strengthen pollution control, sewage disposal, and protection of water resources.Second, limit sand mining in rivers. Third, dispatch reservoir operation schemes toreduce ecology stress. Fourth, change the fluvial morphology to improve the habitatdiversity.