Abstract: In order to reveal the biodiversity of phytoplankton in IPA model and traditional aquaculture ponds, water quality and phytoplankton communities were monitored. The results showed that 64 phytoplankton species were identified in the IPA model, and 49 phytoplankton species were identified in the traditional aquaculture pond, and the average density and biomass of phytoplankton in the IPA model were 113.55×10⁶ ind·L^-1 and 52.79 mg·L^-1, which were higher than the 78.37×10⁶ ind·L^-1 and 23.22 mg·L^-1 in the traditional aquaculture pond. The mean values of Shannon-Wiener diversity index (H') and Margalef diversity index (D) in IPA mode were 3.80 and 2.25 respectively, which were higher than those in the traditional aquaculture pond. Canonical correspondence analysis (CCA) showed that water temperature, potassium permanganate index, total nitrogen, total phosphorus and total organic carbon were the main driving factors affecting phytoplankton in IPA mode; total nitrogen, total phosphorus, total ammonia nitrogen and nitrite nitrogen were the main driving factors affecting phytoplankton in the traditional aquaculture pond.

Key words: internal-circulation pond aquaculture, phytoplankton, canonical correspondence analysis