Abstract: In large landscape lake, the phytoplankton community is regulated in a distinct way from that in the other lakes or reservoirs in the process of construction. To study this dynamics, the phytoplankton and water quality in Lake Songya in Sep. 2013 and Sep. 2014 were sampled and analyzed. Until now, Lake Songya is the largest artificial lake in Hunan Province, China. The results showed that 118 species of phytoplankton belonging to 7 phyla were identified. The phytoplankton had an abundance ranging from 103×104 cells/L to 1514×104cells/L, with an average abundance of 378.5×104cells/L. The phytoplankton community was dominated by Merismopedia tenuissima, Planktolyngbya limnetica, Cyclotella meneghiniana, Chroomonas acuta, and Cryptomons erosa in Sep. 2013, and Microcystis flos-aquae, M. wesenbergii, and Coelastrum microporum in Sep. 2014, respectively. The obviously differences in phytoplankton community between the twice observations were mainly owing to the impounding process which was considered as leading the colonization of new species. Some other factors such as high nutrient concentrations, relative static hydrological conditions and lack of benthic organisms also affected the growth of cyanobacteria. For the sake of the better ecological management of Lake Songya in the future, some suggestions such as removing hygrophytes residues, aquatic macrophyte restoration and stocking zooplankton and zoobenthos were proposed.

Key words: Lake Songya, large artificial lake, landscape water, phytoplankton, ecological restoration