The Study On Aquatic Biodiversity And Ecosystem Health Assessment In The Downstream Of Nengjiang River

In recent years, the city construction, industrial layout, abstraction works and agricultural irrigation have begun to take shape with the rapid development of social economy in Nengjiang River basin, but at the same time, the ecological issues are becoming increasingly prominent. The biodiversity of hydrobios suffered serious threat in the downstream of Nenjiang River, because of the increasingly sharpen of development and utilization strength to water resource and biological resources. In addition, the research data of fishes, zoobenthos and plankton were relative lack, and hydrobios index of biotic integrity was one of the very important indicators in the river ecosystem health evaluation. In order to effectively protect the aquatic species resources of the Nenjiang River and ensure the sustainable use of resources and the healthy development of environment, it was very necessary to carry out the research of aquatic biodiversity.An investigation of plankton, zoobenthos and fishes were conducted in May, July, September, and October in2011, and the investigation of zoobenthos and fishes were carried out in May, July and September in2012. A total of201phytoplankton species were collected, among which the species number of Bacillariophyta was the largest (92species). The average quantity and biomass of phytoplankton were146.41×104ind/L and1.7737mg/L, respectively, and the biodiversity of phytoplankton was abundant from the view of annual average. A total of69zooplankton species were sampled, and the species number of rotifer was the most (40species). The average quantity and biomass of zooplankton were1322.15ind/L and0.6763mg/L, respectively. The diversity of zooplankton was better, and the trend of Shannon-Wiener index, Pielou evenness index and Simpson diversity index was consistent. The diversity of zooplankton was the highest in spring and was the lowest in autumn.151zoobenthos species were collected, and the maximum species number was aquatic insects with114species. The dominant species were Palaemon modestus, Semisulcospira amurensis and Unio dougladiae, and there were30important species. The average density and biomass of phytoplankton were37.40ind/m、3.94g/m2, respectively. The species number of epigrowth feeders was the most with52species in all functional feeding groups. The results of K-dominant curves analysis were consistent with the diversity index. The diversity index of zoobenthos was the highest in spring, followed by summer and autumn in the downstream of Nenjiang River.60fish species were sampled, which account for81.08%of the total fish species in the downstream of Nenjiang River. Only one species Lampetra reissneri (Dybowski) was included in the "China Red Data Book of Endangered Animals-Pisces". The average density and biomass of demersal fishes were66.04ind/m3and178.63g/m3, respectively. Index of relative importance (IRI) value of the top five fish accounted for70.02%of all mantissa. In addition to Carassius auratus gibelio (Bloch) and Silurus asotus (Linnaeus), the other dominant species were small fishes, and the average body weight was less than30g. The community diversity index of demersal fish was lower in the downstream of Nenjiang River, which indicated the community dominant populations was single and miniaturized, the overall quality of fisheries resources declined, and miniaturization offish individuals was obvious.The state of ecological environment and trend of the downstream of Nenjiang River were fully study. An integrated evaluation index system covering hydrobios, water quality, hydrology and water resources, the physical structure of river banks and social service functions, and so on, according to the existing level of technology and monitoring capabilities. Among which index layer included17indicators and element layer included8indicators, and the evaluation and scoring criterion of each layer and indicators was established. The final weight values for river health assessment index system was get using combination weighting method based on game theory. The practicability of above river ecosystem health assessment index system was verified with the downstream of Nenjiang River health assessment as a case study. The grading index scoring, progressively weighted and comprehensive score were adopted in river health assessment. The results suggested the Nierji dam to Tongmen river section belong to unhealthy state, the other river sections belong to health state, and the scoring of Guangrong village to the export of Taoer River was the highest with77.46score. In order to accurately and objectively reflect the river health status of Nenjiang River, the length weight was adopted in scoring hydrobios, water quality, hydrology and water resources, the physical structure of river banks. The final river health assessment index was68.09score in the downstream of Nenjiang River, and this river section belong to healthy state. The existing problems of ecosystem health assessment in the downstream of Nenjiang River were proposed based on the health status and main factors, and corresponding countermeasures and suggestions including strengthening the ecological management, regulating human development activities to reduce the pressure of the water ecosystem and protecting important ecologically sensitive areas and recovering impaired ecosystem were proposed. The ecological protection measures were proposed on "national aquatic germ plasm protection areas of Pelteobagrus ussuriensis (Dybowski) in Daan river section of Nenjiang River" and "national aquatic germ plasm protection areas of Zhenlai river section of Nenjiang River"...