Abstract: In order to better describe the community structure of phytoplankton in the Tianjin waters of the Bohai Bay and its relationship with major environmental factors, three cruise surveys were conducted in 2022, including the spring（May）, summer （August）, and autumn（October）of 2022. The results showed that in the spring, the abundance, Shannon-Wiener diversity index （H’）, Margalef index（D）, and Pielou index（J）of phytoplankton in the reef area were 0.54×10⁴ cell/m³, 1.10, 0.31, and 0.61, respectively, while those in the control area were 0.55×10⁴ cell/m³, 1.30, 0.36, and 0.67, respectively. The abundance, Shannon- Wiener diversity index, Margalef index, and Pielou index of phytoplankton in the summer reef area were 2.51×10⁴ cell/m³, 2.62, 0.70, and 0.90, respectively, while those in the control area were 4.84×10⁴ cell/m³, 2.65, 0.63, and 0.90, respectively. The abundance, Shannon-Wiener diversity index, Margalef index, and Pielou index of phytoplankton in the autumn reef area were 1.30×10⁴ cell/m³, 2.26, 0.44, and 0.96, respectively, while those in the control area were 1.23×10⁴ cell/m³, 2.31, 0.48, and 0.95, respectively. The results indicated that the construction of artificial reefs had an effect in improving the diversity of phytoplankton but weakened the promotion of phytoplankton growth and reproduction with the extension of deployment time. The results of RDA showed that the main environmental factors affecting the community structure of phytoplankton in the Tianjin sea area of Bohai Bay in spring were temperature, salinity, pH, and ammonia nitrogen, while in summer they were temperature, total phosphorus, DO, and nitrite, and in autumn they were total nitrogen, total phosphorus, and ammonia nitrogen.

Key words: Tianjin waters, artificial reefs, plankton, environmental factors, redundancy analysis