Phytoplankton assemblage variation in relation to environmental parameters at two river reaches in Chongming Island

Phytoplankton assemblage and the relative environmental parameters were investigated at different river reaches (the Nanheng River and Laoyao River) monthly from September 2008 to August 2009. In November and May during the one-year period, large-scale water diversion from the Yangtze River had been carried out through the Nanheng River. Redundancy analysis (RDA) was used to discover the most important regulating parameters in relation to seasonal and spatial variations in different rivers. The RDA triplots showed that at the Nanheng River water temperature (Tern), chlorophyll a (Chl-a), conductivity (Ec), water diversion (H), total nitrogen (TN), and ortho-phosphorus (PO₄^3-) had the most profound impacts on the phytoplankton assemblage, while at the Laoyao River, only water temperature (Tern) and conductivity (Ec) were the most important. Our results suggest that timely water diversion from the Yangtze River could improve the water quality by decreasing nutrients concentration as well as phytoplankton biomass.