Siagian, MadjuSiregar, Syamaruddin2014-01-302014-01-302014-01-30wahyu sari yenihttp://hdl.handle.net/123456789/5431Study on the types and diversity of phytoplankton in the Koto Panjang Reservoir (Hydro-Electric Power Plant Reservoir), Kampar, Riau, Indonesia, have been conducted from May to October 2009. For water quality analysis, samples of water were collected every month from 6 stations on the reservoir which consisted of 1 station on the riverine zone, 2 stations on the transition waters, and 3 stations on the lacustrine zone. The components of the samples have been taken vertically as well as horizontally. The diversity of the phytoplankton varies according to the zones, and there were 4 classes of phytoplankton which were consist of 6 types of Bacillariophyta, 5 types of Chlorophyta, 3 types of Cryssophyta, and 3 types of Cyaniphyta. Therefore, there were 17 types of phytoplankton have been recorded. The abundance of phytoplankton at the lacustrine zone were higher, compared to transition zone and riverine zone Such condition was estimated die to the higher of N and P ratio on the lacustrine zone compared to the transition and riverine zone. The analysis of index diversity, domination and similarity indicated that the condition of the reservoir still in suitable (balance) condition for phytoplankton without dominant species.enKoto Panjang reservoirwater qualityphytoplanktonUR-Scientific Work Lecturer