Abstract: To clarify the seasonal variation and influencing factors of phytoplankton functional groups in aquatic ecosystems of semi-arid lakes in northern China, we investigated phytoplankton community and water environmental factors at 14 sampling sites in Chagan Lake in summer (August), autumn (September) in 2020 and spring (May) in 2021. We analyzed the seasonal succession and influencing factors of phytoplankton functional groups in Chagan Lake. The results showed that a total of 94 species of phytoplankton from seven phyla were identified, mainly from green algae and diatoms (46 species of green algae, accounting for 48.9%, and 24 species of diatoms, accounting for 25.5%). The phytoplankton could be divided into 20 functional groups. The important functional groups were X2, J, and C, which were dominant throughout the year. The seasonal changes of those groups followed X2+J+C (spring) → X2+J (summer) → X2+J (autumn). The results of redundancy analysis showed that total nitrogen, total phosphorus, chemical oxygen demand (COD_Mn), pH, and water temperature were the most important environmental factors affecting the functional groups of phytoplankton.

Key words: phytoplankton, functional group, Chagan Lake