Due to its complex in estuarine ecosystem, environmental factors were crucial to the distribution of phytoplankton [8]. Phytoplankton community in Xiaoqing River estuary in autumn 2008 was composed
of diatom, chlorella, cyanobacteria, and zooxanthellae.
Moreover, the eight dominant species were belonged to the four phyla. Locations of phytoplanctonic species in CCA bioplot indicated its dependence
on environmental factors [9]. The ecological adaptation of species with close position was similar. Chlorella, cyanobacteria, and zooxanthellae were mainly concentrated in the third quadrant corresponding
to the environment of high concentrations of COD, NO2--N, and NO3--N and low S. The demand for
PO43--P of chlorella and cyanobacteria was higher than diatom. Chlorella, cyanobacteria, and zooxanthellae identified in this investigation were common freshwater species with tolerance of pollution. For example, Scenedesmus armatus and Scenedesmus quadricauda were the indicators of moderate pollution and Oscillatoria Sp. was the indicator of organic pollution. That was in agreement with CCA bioplot.