Responses of Phytoplankton and Periphyton to Environmental Variations in Urbanizing Tidal Rivers

Phytoplankton and periphyton assemblage investigation were performed at a typical urbanizing tidal river and its major tributary in Shanghai, China from April 2005 to May 2006. A further analysis of the relationship between environment variables and species distribution revealed the differences of the two assemblage´s responses to both of natural and anthropogenic environmental changes. Chlorophytes (>50%) were the most important taxonomic group in phytoplankton, while Bacillariophytes (>60%) exhibited numerically dominates in periphyton. The peak density of phytoplankton (1.91times10⁴ ind-L^-1) occurred at the downstream of rivers in summer, while periphyton ranged from over 8,000 ind-cm^-2 at the middle reaches in dry season (autumn), to less than 4,000 individuals at the downstream in the moist spring season. Canonical correspondence analysis (CCA) suggested an interaction between nature (water temperature) and human disturbances on the distribution of species, however, nutrients were the important anthropogenic influence factors in assemblage variables. Phytoplankton responded more quickly to environmental changes than periphyton and appeared to be more sensitive indicators of changes in water quality.