Phytoplankton Community Composition And Its Relationship With The Water Quality In Summer And Autumn Of Wuliangsuhai Lake

Phytoplankton composition and characteristics of lake is the water quality evaluation and important indicators of ecosystem health assessment.Wuliangsuhai Lake is one of the largest fresh water lake in western China。 It is important base of water conservation, water storage and water diversion of upper reaches of the Yellow River. But water eutrophication was serious because of great quantities farmland return water from hetao irrigation area, industrial wastewater and domestic sewage discharged into Wuliangsuhai Lake in recent years. This paper analyzes the phytoplankton community characteristics and its relationship with water quality which was reveal the relationship with phytoplankton species, community structure and water quality. The purpose of these are provide basic data and theoretical reference of predict the phytoplankton, wetland ecosystem restoration and reconstruction of Wuliangsuhai Lake. (1) During the study period were identified177species of phytoplankton, belonging to83genera and7phyla. The Chlorophyta:71species,36kinds of Bacillariophyta, Cyanophyta35, Euglenophyta,20; Cryptophyta:7; Pyrrophyta4species; Chrysophyta:2.(2) Phytoplankton community of7dominant species in summer were Oscillatoria tenuis、Oscillatoria amphibian、Phormidium tenue、Anabaenpsis arnoldii、Raphidiopsis sinensia、Fragilaria crotomensis and Chamydomonas ovalis。 The9dominant species in autumn were Cyclotella bodanica、Cyclotella Kutzingiana、Fragilaria crotomensis、Nitzschia、Chroomonas acuta、 Chamydomonas ovalis、Ankistrodesmus spiralis、Chamydomonas globosa and Oscillatoria tenuis. The number of dominant species in summer is more than that of in autumn.(3) No matter from the perspective of the variety and abundance of algae, diatoms、green algae and blue algae are advantage groups of Wuliangsuhai Lake. The succession of community type reflected from blue algae to diatoms by summer to autumn.(4) From inlet to outlet, the basic downward trend of nutrient content in water, phytoplankton abundance gradient changes with water content of nutrients, that is one of the main factors to determine phytoplankton abundance of Wuliangsuhai Lake (5) Through related analysis, that’s showed a highly significant correlation between the density of phytoplankton with total phosphorus, total nitrogen, conductivity, dissolved oxygen, and are significant correlation with the NH4+-N of overlying water. Therefore, the key point of Wuliangsuhai Lake wetland ecosystem restoration and reconstruction on prevention and control is exogenous nutrient emission.