Hayati, Yaserli2012-11-092012-11-092012-11-09sumarnihttp://repository.unri.ac.id:80/handle/123456789/428The research was conducted in April-Mei 2012 in Lake Singkarak Jorong Ombilin Tanah Datar District of West Sumatera Province. Types of phytoplankton are found during the research in Jorong Ombilin consisted of four classes, and (15 types), namely the class Bacillariophyceae (3 types), class Chlorophyceae (8 types), class Cyanophyceae (3 types) and the class Xanthophyceae (1 types). Abundance values of phytoplankton in the waters of Lake Singkarak Jorong Ombilin, ranging from 2107 – 2935 cell/l, diversity index (H’) around 1,920 – 2,356. Phytoplankton species dominancy index (C) around 0,105 – 0,159 and equitability index (E) around 0,912 – 0,977. General water quality parameter are follow: temperature 270C – 290C, pH 6, dissolved O2 : 4,17 mg/l – 4,63 mg/l, CO2 9,38 mg/l – 13,54 mg/l, Nitrate : 0,0054 mg/l – 0,0107 mg/l and phosphate : 0,0204 mg/l – 0,0513 mg/l. Based on the diversity of species diversity is to have a different distribution of phytoplanktonotherLake Singkarakphytoplanktondiversity indeksdominancy indeksequitability indeksArticle