Nutrient distribution, phytoplankton size structure and phytoplankton cell associated phosphorus characters of nanophytoplankton and picophytoplankton were studied during the two cruises in May and September of 2014. The results show that nutrients distributions have seasonal variation in Sanggou Bay due to aquaculture activities. Nutrient concentrations are lower in spring than in autumn. In spring and autumn, phosphorus would limit phytoplankton growth. Content of Chlorophyll a decreases from

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... the east of Sanggou Bay to the west in spring, while in autumn the distribution trend is opposite. Phytoplankton is mainly dominated by nanophytoplankton in spring, while in autumn both nano-and pico-phytoplankton are the dominance of the community. From bay mouth to bay head, average size of phytoplankton is reduced both in spring and autumn. Intracellular phosphorus is dominance of nano-and pico-phytoplankton total cellular phosphorus, which contributes to 64% -93%. The results of correlation analysis between cell associated phosphorus contents and nutrients indicated a distinct positive correlation between total cellular phosphorus, intracellular phosphorus of nanophytoplankton and DIP, DSi (r ≥ 0.796), but no correlation between cell associated phosphorus of picophytoplankton and nutrients (r < |0.402|).