Abstract: To understand the temporal and spatial characteristics of phytoplankton community structure in Wanfeng, a deep altiplano reservoir, phytoplankton was measured in September, 2009 and January, 2010. Forty-nine species of algae were identified. In summer the community was dominated by Cylindrospermopsis rackiborskii at the surface (0-10 m) and at the bottom (>60 m) Synedra ulna and Cyclotella meneghiniana became dominant, but in winter the community was dominated by Synedra ulna and Cyclotella meneghiniana. The phytoplankton abundance ranged from 13.0×10⁴ to 54.6×10⁴ cells·L^-1 in summer and 17.43×10⁴ to 25.28×10⁴ cells·L^-1 in winter. The maximum phytoplankton abundance was at Yeyatang (S2), but the minimum phytoplankton abundance was at Baai (S4). In summer, phytoplankton collected at the surface (0-10 m) was primarily composed of cyanophyta. The highest percent composition of cyanophyta was 90.3% at Daba (S1). Shannon diversity index was higher in summer than in winter, but the evenness was lowest at the surface in summer. In winter, phytoplankton mainly distributed at the surface (0-10 m) and at the mid-level (10-50 m), and was primarily composed of bacillariophyta. The percent composition of bacillariophyta was above 90% in all water layers. Judged by phytoplankton community structure and abundance, Wanfeng Reservoir is mesotrophic in summer. Water quality was better in winter than in summer. A relationship between phytoplankton abundance, temperature, and water depth was obvious in winter and summer.

Key words: Mining areas, Environmental management, Ecological planning, Managing planning