Study On Community Ecology Of Macrobenthos In Daning River

Macrobenthos were collected from eight sampling sites of Daning River including Wushan, Shuanglong, Dachang, Longxi, Wuxi, Ningchang, Xiabao and Xujia at low water-level period (May to June,145 m) and high water-level period (November to December,170 m) of the Three Gorges Reservoir from 2011 to 2013, and from June 2013 to March 2014, macrobenthos were sampled respectively in March, June, September and December. The basic characteristics of macrobenthos in Daning River, including the species composition and distribution, the differences of community during different water level periods, seasonal dynamics of macrobenthos community and water quality, relationship with environmental factors were studied based on the macrobenthos investigations. The main results were summarized as follows.1. Ninety-one species belonging to 69 genera,55 families,16 orders,6 classes and 4 phyla, were collected in Daning River. Among them,72 species were aquatic insects, accounting for 79.12%; Mollusks including 8 families, accounting for 8.79%; 3 class belonging to Oligochaeta accounting for 6.60%; only 2 species belonging to Crustacea accounting for 2.20%; Turbellaria has one species(Dugesia japonica), accounting for 1.10%; and the others accounted for 2.19%. Branchiura sowerbyi, Limnodrilus hoffmeisteri, Hippeutis umbilicalis, Dugesia japonica, Paracladius, Hydropsychidae, Polycentropodidae, Iron, Cinygmina, Baetis and Antocha were frequent species.2. Qualitative and quantitative surveys were conducted on macrobenthos at low water-level period (145 m) and high water-level period (170 m) of the Three Gorges Reservoir from 2011 to 2013, to study the characteristics and differences of the macrobenthos community of Daning River. The result showed that the macrobenthos density and biomass were 80.32±32.14 ind./m and 1.44±0.45 g/m2 respectively during low water-level period; while the density and biomass were 133.82±46.94 ind./m2and 1.53±0.51 g/m2 during high water-level period. Tubificidae dominated the lentic zones, and aquatic insects dominated the lotic zones. Macrobenthos species composition and distribution was significantly different between high and low water-level period, also it was the same with the lotic water area and the static water area(P<0.05). During the different water-level periods, the density and biomass showed significantly different (P<0.05), and the dominant species and their relatively abundance showed a great difference. The diversity index indicated that biodiversity in high water-level period was higher than that in low water-level period, and biodiversity in lotic water area was significantly higher than that in the static water area (P< 0.05). Multidimensional Scaling (MDS) analysis and cluster analysis showed that macrobenthos Community structure had obviously differentiation in both spatial scale and temporal scale.3. To study the seasonal dynamics of macrobenthos community in Daning River, the individuals of macrobenthos were quantitatively monitored. A total of 85 taxa were collected, among which, Hydropsychidae, Polycentropodidae, Cinygmina, Naididae, Antocha and Hippeutis umbilicalis were the dominantgroups, and their compositions varied with seasons. Aquatic insects were the majority. Diversity index studies showed that the macrobenthos community was most complicated in summer, followed by which in spring and winter, and the simplest in autumn, Summer floods had a obvious influence on the macrobenthos community structure. The component of functional feeding groups in Daning River was significantly different in numbers and proportions in different seasons. Canonical correspondence analysis (CCA) suggested that the factors affecting the macrobenthos community were dissimilar among seasons. Water temperature^ depth, transparency, conductivity and dissolved oxygen were the main environmental factors, which affected macrobenthos of Daning River significantly, Water depth had definite effect on Tubificidae.4. Based on the macrobenthos monitoring data of Daning River from 2011 to 2014,We tried to find a suitable method which was used to evaluate the water quality of the river. The results showed that EPT index could not reflect the water quality and the difference of each sampling site.The diversity indices and Beck index reflected water quality characteristics in a certain extent, but the accuracy was not enough FBI index could be a very good reaction to the water quality conditions. The general water quality of Daning River was good according to the water quality assessment from 2011 to 2013. The water quality of the upstream and downstream showed significantly different. The water quality of the upstream was good, while the downstream water was poor. All the water quality indices of Daning River varied from 2011 to 2013.The static water area was exist a certain degree of pollution while the lotic water area in upstream was clean, and this situation may exist for a long time.