Seasonal variations in phytoplankton community structure were studied in Sanggou, Ailian, and Lidao Bays in eastern China. The researchers looked at different types of phytoplankton in the bays during spring, summer, autumn, and winter. They found that diatoms were the most common type of phytoplankton throughout the year, with dinoflagellates being more dominant in summer. Phytoplankton abundance was highest in summer and lowest in autumn. The diversity and evenness of phytoplankton species varied across seasons, with autumn having the highest diversity. Phosphate levels were identified as a key factor influencing the presence of certain phytoplankton species.