Abstract:

 To understand the community structure of phytoplankton and its relationships with environmental factors among three Yangtze River-connected lakes in Anhui, we analyzed the phytoplankton species composition, abundance, biomass, and environmental factors at three Yangtze River-connected lakes (Longgan Lake, Daguan Lake and Huang Lake) in September (autumn) of 2017. The results showed that 107 phytoplankton species (including varieties) were recorded, belonging to 7 phyla and 50 genera. Chlorophyta and Bacillariophyta dominated the phytoplankton community, which accounted for 50.47% and 23.36% of total species, respectively. The dominant species included Scenedesmus quadricauda,Melosira granulate var. angustissima, Merismopedia minima,Oscillatoria subcontortaand Aphanizomenon flos aquae. The community was dominated by Cyanophyta and Bacillariophyta in Longgan Lake, by Chlorophyta, Bacillariophyta and Cyanophyta in Daguan Lake and Huang Lake. Phytoplankton abundance ranged from 2.37×10⁴-44.99×10⁴ cells·L^-1, while phytoplankton biomass was 0.017-0.432 mg·L^-1. Across the three lakes, the abundance of Cyanophyta was higher, and Chlorophyta and Bacillariophyta biomass were higher. The phytoplankton abundance and Shannon diversity showed substantial spatial variation. Lake connectivity and human activities affected the spatial variation of phytoplankton community across the three lakes. Results of redundancy analysis showed that the main environmental factors affecting phytoplankton community structure differed among the three lakes. Water depth and water transparency significantly affected phytoplankton community structure of Longgan Lake. Water depth and water temperature were the driving factors in Daguan Lake. Water conductivity, dissolved oxygen, and pH played key roles in Huang Lake.

Key words: phytoplankton, community structure, environmental factor, redundancy analysis, Yangtze River-connected lake.