Abstract:
This research has been conducted in July 2012 in Lake Toba. The research used survey method. There were 3 station, Station 1: The litoral zone of resident activities such as washing, gardening, farming, tourism, and chart for fishing, Station 2: located in the middle of Lake Toba, Station 3: Outlet of Lotung river, around 500 meters from the station 1. Samplings were conducted 3 times, once/week. This research aim to know abundance of phytoplankton in Lake Toba.
The results showed 47 kinds of phytoplankton that classified into 5 classes, there were :Chlorophyceae (15species), Cyanophyceae (6species), Bacillariophyceae (12species), Chrysophyceae (4species), and Xanthophyceae (10species). The average of phytoplankton abundance around 77.076-116.993 cel/l, Diversity index (H') of phytoplankton around 2,845-2,891 and Domination index (C) around 0,052-0,065. Whereas water quality parameter such as temperature around 28,3-30oC, Transparency around 433,3-650 cm, Depth around 20-70 m, pH 6, Dissolved Oxygen around 4,3-6,3 mg/l, Free carbondioxide around 3,73-5,03 mg/l, Nitrate around 0.01-0.02 mg/l, Phosphate around 0,023 mg/l. Based on abundance of phytoplankton, concluded the stations of research in lake Toba mesotrophic water
