Phytoplankton community structure and its environmental adaptation in Fangcheng coastal waters

The seasonal surveys on phytoplankton community and their environmental variables were conducted in Fangcheng coastal waters from September 2014 to August 2015. A total of 130 species of phytoplankton were identified (106 species of Bacillariophyta, 19 species of Pyrrhophyta, 2 species of Chrysophyta, 2 species of Cyanophyta and 1 species of Chlorophyta). The abundance of phytoplankton ranged from 1.50×10⁶ cells · m^-3 to 797.18×10⁶ cells · m^-3 (average:122.91×10⁶ cells · m^-3) and had significant difference among seasons(P < 0.01)in a descending order of autumn>summer >winter >spring. The Shannon-Wiener diversity index ranged from 0.37 to 4.00 with an average of 2.60, indicating slight environmental pollution. The cluster analysis of species similarity between sites has found a coastal group with water depth of less than 10 m and a middle group with water depth between 10 m and 20 m (P=0.001). The result of redundancy analysis (RDA) shows that the eight environmental factors explained 57.51%~72.65% spatial variation of phytoplankton abundance. Depth, water temperature, dissolved oxygen and concentrations of phosphates were the dominant factors affecting the phytoplankton community in Fangcheng coastal waters and their importance varied with seasons.