摘要：This research aimed to analyze the water quality of Maninjau Lake (0°19'N 100°12'E, 0,317°S 100,2°E), West Sumatera, Indonesia by phytoplankton as bioindicator of water quality. The quality of water was determined by identified the phytoplankton. Analyzed phytoplankton as bioindicator with Diversity Index (H′), Evenness Index (E) and Dominance Index (D). The abundance of phytoplankton ranged 273-378 cell/liter, consists of three division which are Cyanophyta, Chrysophyta, and Chlorophyta. The average value of Diversity Index (H′) is 3.52 show that the waters classified as moderate, or indicating half-polluted waters. The average value of Evenness Index (E) is 0.92 indicating that the evenness of species is medium. The average value of Dominance Index (C) is 0.12, meaning there is not any phytoplankton dominance in the waters. Maninjau Lake is slightly polluted caused by organic and inorganic contaminants from many activities surrounding especially household and fish breeding activities. The research show that Maninjau Lake is in oligotrophic state or nutrient-deficient waters.
