Abstract: To understand the responses of phytoplankton functional groups to connectivity and heterogeneity in the connected river-lake system of Guangzhou Haizhu National Wetland Park, we conducted a quarterly survey on the phytoplankton community structure and environmental characteristics in the Shiliugang River and Haizhu Lake in 2021. A total of 168 phytoplankton species belonging to 6 phyla and 76 genera were detected, mainly consisting of Chlorophyta, Bacillariophyta, Euglenophyta, and Cyanophyta. The average abundance of phytoplankton in Haizhu Lake (64.76×10⁶ cells·L^-1) was significantly higher than that in Shiliugang River (24.09×10⁶ cells·L^-1) (P<0.05), while Shannon diversity index and Pielou evenness index in the Shiliugang River were significantly higher than those in Haizhu Lake (P<0.05). The phytoplankton in the connected river-lake system of Guangzhou Haizhu National Wetland Park could be classified into 28 functional groups according to their ecological functions. The dominant functional groups were group L_o, group J, and group P, which was represented by Merismopedia, Scenedesmus, and Aulacoseira, respectively. Water temperature, ammonium nitrogen, and total phosphorus were the main environmental factors affecting the dominant functional groups. The results indicate that the connected river-lake system has reached the level of eutrophication.

Key words: national park, river-lake connecting water system, phytoplankton, functional group, biodiversity, water quality evaluation.