关键词: 采煤沉陷湖泊, 浮游植物, 环境因子, 冗余分析（RDA）

Abstract: In order to study space-time variation of phytoplankton and its relationship with water environmental factors in Digou coal mining subsidence lake, the phytoplankton community was investigated from August 2015 to June 2016. Results showed that a total of 155 species of phytoplankton were identified, which belong to 8 phyla, 10 classes, 17 orders, 32 families and 62 genera. The species number of Chlorophyta, Bacillariophyta and Cyanophyta accounted for more than 75% of phytoplankton species. During the investigation, the main dominant species were Phormidium tenu, Oscillatoria acutissima, Synedra ulna, Chroomonas acuta, etc. The variation range of the density and biomass of phytoplankton respectively was 22.68×105-290.24×105cells/L and 2.47-7.41 mg/L. The density of phytoplankton changed significantly (F=15.48, P<0.05) , and the overall trend was to rise after the first drop. Biomass exhibited a similar temporal behavior to that seen in the density. The density and biomass of Cyanobacteria were dominant in most of the time. The spatial differences of Shannon-Wiener index (H′) were obvious, and water system communication improved phytoplankton diversity in subsidence lake. Redundancy analysis (RDA) indicated that water temperature, transparency, total phosphorous and nitrate nitrogen were important factors affecting the variations of phytoplankton community in the subsidence lake, and water temperature was the key factor affecting the temporal variation of phytoplankton. Digou mining subsidence lake was eutrophic, and the eutrophic characteristion of phytoplankton community was obvious. Meanwhile, the lake had a potential risk of blue algae bloom.

Key words: coal mining subsidence lake, phytoplankton, environmental factors, redundancy analysis (RDA)