摘要:This study aims to determine the condition of the waters of the North Sunter Reservoir through the distribution pattern of phytoplankton and the influence of the physical and chemical aspects of the waters on the presence of phytoplankton. The study was conducted from August 2017 to January 2018 with 12 sampling points. Phytoplankton sampling was performed vertically on two different segments each with a depth range of 0-1.9 meters and 1.9-3.9 meters using planktonet number 25. Research shows that phytoplankton can live on the bottom of the reservoir with little sunlight conditions due to the large concentration of nitrate and phosphate. The abundance of phytoplankton in segment 1 (7,104-219,820 cells/L) and segment 2 (9,771-132,313 cells/L) consisted of 4 phyla namely Cyanophyta (8 genera), Chrysophyta (10 genera), Chlorophyta (16 genera), and Euglenophyta (4 genera). The index of the diversity of phytoplankton in segment 1 (1.22-2.39) and segment 2 (1.14-2.13), everness index on segment 1 (0.47-0.85) and segment 2 (0.45-0.85), dominance index in segment 1 (0.12-0.76) and on segment 2 (0.16-0.52). The distribution of phytoplankton in North Sunter Reservoir is uniformly distributed by current and nutrients. This research serves as an adjunctive decision-making factor over the appropriate follow-up management methods.