1988—2017年洞庭湖浮游植物的群落演变

1988-2017年洞庭湖共记录浮游植物8门110属，其中蓝藻门15属、绿藻门45属、硅藻门28属、裸藻门7属、甲藻门4属、隐藻门4属、金藻门5属、黄藻门2属。洞庭湖所出现的物种主要是绿藻门、硅藻门和蓝藻门，分别占全湖种类的40.9%、25.5%和13.6%，而其他5门只占20.0%。洞庭湖浮游植物优势种群从20世纪90年代初的以隐藻和硅藻为主转变为目前以硅藻和绿藻为主，在个别湖区（如大小西湖）已经出现以蓝藻为优势种群的现象，洞庭湖已经到了由中营养到轻度富营养化的转折点。洞庭湖浮游植物密度呈显著上升趋势，由20世纪90年代左右的2.06×10⁴ cells/L上升到目前的32.3×10⁴ cells/L。东洞庭湖浮游植物种类和密度显著高于西洞庭湖和南洞庭湖。近30年来分析表明浮游植物密度和种类都与总氮显著正相关，都与溶解氧显著负相关。

Phytoplankton Community Succession Trends of the Dongting Lake from 1988 to 2017

From the investigation during 1988-2017, phytoplankton species belonging to 8 phyla and 110 genera were recorded in the Dongting Lake, including 15 genera from the phylum Cyanophyta, 45 genera from Chlorophyta, 28 genera from Bacillariophyta, 7 genera from Euglenophyta, 4 genera from Pyrrhophyta, 4 genera from Cryptophyta, 5 genera from Chrysophyte and 2 genera from Xanthophyta. Within the phytoplankton assemblages in the Dongting Lake, the dominant groups were Chlorophyta, Bacillariophyta and Cyanophyta, which accounted for 40.9%, 25.5% and 13.6% of total numbers of species, respectively. Whereas others five phyla only accounted for 20.0% of total species richness. The dominant phyla of phytoplankton communities significantly changed through time:from Cryptophyta and Bacillariophyta in the early 1990s to current Bacillariophyta and Chlorophyta, and even with Cyanophytaas the dominant group in specific lake regions. Dongting Lake has reached the turning point from mesotrophication to light eutrophication. The phytoplankton density increased significantly through time, from 2.06×10⁴ cells/L in the early 1990s to 32.3×10⁴ cells/L at present. The species richness and density of phytoplankton in the East Dongting Lake were significantly higher than that in the West and South Dongting Lake.Correlation analysis showed that phytoplankton density and species number were significantly positive correlated with total nitrogen (TN), but negative correlated with dissolved oxygen (DO).