To understand the structure of the plankton community and the ecological niche characteristics of their dominant species, sampling surveys of plankton were conducted in Baiyangdian Lake in the spring （March）, summer （July）, and autumn （September） of 2022. The changes in the plankton community during the three seasons were analyzed by constructing ecological network diagrams, non-metric multidimensional scaling analysis （NMDS）, and the ecological niche width. The niche overlap of zooplankton dominant species was evaluated by the improved Levins' formula and Petraitis' index. The interspecific connectivity of dominant species was judged using the chi-square test and interspecies connectivity coefficients. The results showed that the niche width of plankton in the whole area was low. Zooplankton was dominated by rotifers, and phytoplankton was dominated by diatoms, cyanobacteria, and green algae. There were significant seasonal changes in the community structures of plankton. Compared with that in summer and autumn, there were fewer species of plankton in spring and lower interspecies connectivity. The overlap of dominant species of zooplankton was high in summer, and the interspecific competition was intensified, whereas the interspecific overlap of phytoplankton was at a low level in all three seasons. There was a significant positive correlation （W > χ20.05） between phytoplankton in summer and autumn, and the community structure was stable. The interdomain ecological network of zooplankton and phytoplankton showed a high negative correlation ratio in autumn, especially between copepods and cladoceras of zooplankton and chlorophyta and cyanophyta of phytoplankton. The plankton species in Baiyangdian Lake were abundant, with obvious seasonal differences. The dominant species were mainly a narrow ecological niche. The plankton community was generally in a stable state, and there was a strong predation relationship between copepods and cladoceras and green algae and cyanobacteria.
Keywords: Baiyangdian Lake; ecological network; ecological niche; interspecies connectivity; plankton.