Abstract

Similar to other plants, animals and microorganisms, phytoplankton has diversity in many respects, such as species diversity, morphological diversity and ecological diversity. Seasonal variations of species composition and diversity were the greatest difference of phytoplankton from other living populations. Species diversity and diversity indices of phytoplankton and growth related factors were investigated in Zhangjiang seawaters in winter and summer seasons. 15 species appeared only in winter, 49 species appeared only in summer, and 33 species could survive in winter and summer seasons. And the seasonal variations of species richness and abundance were greatly related with water temperature, salinity and other growth related factors. Thalassionema nitzschioides, Nitzschia sp. and Coscinodiscus bipartitus were the dominant species in winter： Bacteriatrum varians, Chaetoceros subescundus and Nittzchia sp., etc were the dominant species in summer. Species diversity index （H）, evenness （J） and abundance （d） in summer were higher than in winnter. Otherwise. the dominance （D） was higher in winter than in summer. Furthermore, more red-tide algae appeared in summer than in winter.