Spatial and Temporal Distribution Characteristics of Water Quality in Shahe Reservoir within Tianmuhu Reservoir and its Relationship with Phytoplankton Community

Monthly investigation was made on water quality and phytoplankton community structure in Shahe Reservoir in 2012. Temporal and spatial distribution characteristics of water quality and its effect on phytoplankton community succession were analyzed through principal component analysis and canonical correspondence analysis. The results indicated there was a close relationship between the temporal and spatial differentiation of water quality and distribution of phytoplankton community structure. Obviously seasonal and spatial variations were observed in water quality factors such as transparency,suspended solids,permanganate index,chlorophyll a,total nitrogen and total phosphorus in Shahe Reservoir. Meanwhile,phytoplankton biomass and community structure were also presented significantly seasonal succession,which was closely related with temperature,pH,dissolved total nitrogen and transparency based on the canonical correspondence analysis,with the biomass of cyanophyta and bacillariophyta positively correlated with temperature,dissolved total phosphorus and negatively correlated with nitrate. Synedra was the dominant species in spring in terms of phytoplankton biomass and also the key impact factor for transparency in Shahe Reservoir. The abundance of phytoplankton was dominated by phormidium in 2012,and the abundance of bacillariophyta and cryptophyta significantly increased in winter and spring. Nitrogen and phosphorus also showed significantly temporal variations in Shahe Reservoir based on principal component analysis,and the effects of nitrogen and phosphorus on water quality varied in different seasons. Therefore,to control water eutrophication and protect water quality,it is crucial to decline the concentration of nitrogen and phosphorus according to the temporal variations of nitrogen and phosphorus. Furthermore,highly developed tea garden and tourism in the catchments of Tianmuhu Reservoir are two important factors influencing water quality.