Variation Tendency of Phytoplankton in Dongting Lake from 2017 to 2021
From the investigation during 2017-2021,phytoplankton species belonging to 8 phyla and 99 genera were recorded in Dongting Lake,including 20 genera from Cyanophyta,39 genera from Chlorophyta,24 genera from Bacillariophyta,3 genera from Pyrrhophyta,6 genera from Euglenophyta,4 genrera fron Cryptophyta,1 genera from Chrysophyte and 2 genera from Xanthophyta.Within the phytoplankton assemblages in Dongting Lake,the dominat groups were Chlorophyta,Bacillariophyta and Cyanophyta,which accounted for 39.4%,24.2%and 20.2%of total numbers of species,respectively.Whereas others 5 phyla only accounted for 16.2%of total numbers of species richness.Compared with the data collected during 1988-2017,the proportion of Chlorophyta in the phytoplankton of Dongting Lake during 2017-2021 decreased by 1.5%,that of Bacillariophyta decreased by 5.3%,and that of Cyanophyta increased by 2.4%.From 3.23×105 cells/L during 1988-2017 to 5.87×106 cells/L at 2017-2021.The phytoplankton density of East Dongting Lake was 1.518×107 cells/L,which was 1.187×106 cells/L of South Dongting Lake,and 1.248×106 cells/L of West Dongting Lake.The density of phytoplankton in East Dongting Lake was significantly higher than that in West and South Dongting Lake.