Abstract: To provide reference for the conservation of marine ecosystems near Taishan, seasonal variation of phytoplankton community and environmental factors in sea waters near Taishan were investigated from December 2015 to September 2016. A total of 113 species were identified, belonging to 64 genera and six classes. The most diverse group was the diatoms (67 species from 31 genera), accounting for 59.2% of the total recorded species, followed by dinoflagellates (18 species, 10 genera), which accounted for 15.9% of the total recorded species. Diatoms were predominant in species composition and cell abundance. Dinoflagellates and green algae were the second and the third major group, peaking in spring and summer, respectively. The annual average cell abundance of microalgae was 7.06×10⁵ cells·L^-1, peaking in spring (2.65×10⁶ cells·L^-1), followed by summer (6.3×10⁴ cells·L^-1), autumn (5.6×10⁴cells·L^-1), and winter (5.4×10⁴ cells·L^-1). The dominant species were Leptocylindrus danicus,Chaetoceros lorenzianus,Coscinodiscus radiates,Ditylum brightwellii, Skeletonema costatum, and Phaeocystis globosa. Among them,S. costatumwas dominant in all seasons. The annual averageShannon diversityindex, Margalef diversity index, Pielou evenness index were 2.98, 3.34 and 0.69, respectively. The effects of water temperature, salinity, pH, chemical oxygen demand (COD), nitrate and active phosphate on the phytoplankton community structure varied among different seasons. Salinity, pH and nitrate were the driving factors of cell abundance peak in spring.

Key words: carbon isotope, net primary productivity, climate change, tree ring