Abstract: Based on the survey from November 19 to December 24, 2006, the species composition, assemblage structure, and cell abundance of phytoplankton on the continental shelf of East China Sea (24.0°-32.0°N，120.0°-128.0°E) were studied. The phytoplankton flora in the survey area included 145 taxa, belonging to 64 genera of 4 classes (including uncertain species). Bacillariophyta was the dominant functional group, followed by Pyrrophyta. The dominant species in turn were Thalassionema nitzschioides, Thalassiosira rotula, Leptocylindrus danicus, Guinardia striata, Pseudo-nitzschia pungens, and Trichodesmium thiebautii. The cell abundance of the phytoplankton ranged from 0.09 to 35.11cells·ml^-1, with an average of 4.92 cells·ml^-1. In the autumn, Bacillariophyta abundance discriminated the surface pattern of the phytoplankton, and the higher abundance area was located at the northeast part of offshore regions, with the cell abundance reached 30 cells·ml^-1. On the whole, the cell abundance of Bacillariophyta and Pyrrophyta was concentrated in surface water, and it reduced rapidly from surface layer down to the bottom. According to the section distribution, the phytoplankton mainly concentrated in surface water, and also, in the middle and bottom layers for some stations. The average of Shannon-Wiener indices of phytoplankton assemblage was 2.80, with the higher values occurred in the northeast and southeast of the survey area. The average of Pielou’s evenness of phytoplankton assemblage was 0.81, and the higher value was located at the middle of the survey area. The surface horizontal distribution of Shannon-Wiener indices was coincided with that of phytoplankton cell abundance. According to the Pearson correlation analysis, the factors that significantly affected the growth of the phytoplankton were nitrite, dissolved organic nitrogen (DON), and temperature.

Key words: photosystem Ⅱ, oxidative stress, non-invasive micro-test, sodium tungstate