Nygard Index can be used to determine the trophic state of waters. Calculation of this index is based on the number of phytoplankton species that are belonged to these following groups, namely Chlorococcales, Myxophyceae, Centric diatom, Euglenophyceae, and Desmidiaceae. To understand the trophic state of the Perupuk Lake, a research has been conducted in June-July 2019. There were three sampl…