Distribution of phytoplankton based on the water quality of Bengawan Solo River, Central Java

Bengawan Solo River is the longest river on the island of Java, and it has 548.53 km in length. The river has an important meaning for the community both for agriculture, tourism, plantations and fisheries, as well as for the life of aquatic organisms. Phytoplankton in rivers have a role in fishery resources, being a primary producer and can be used as an indicator of the quality of the aquatic environment. Distribution phytoplankton abundance in waters will be affected by water quality and physiology. This study aims to determine the abundance and diversity of phytoplankton in Bengawan Solo. The research was conducted in April and August 2020. The research stations selected to represent the upstream locations were Gajah Mungkur Wonogiri Reservoir and Bendung Colo Sukoharjo. Kampung Sewu Solo and Bison Karanganyar research stations represent locations where there are industries. Meanwhile, Tenggak Sragen, Ngawi, Kanor Bojonegoro stations are three locations which are located on the downstream sector. The results showed that during the dry season, distribution of abundance of phytoplankton was higher (259 cells L-1) than during the rainy season (192 cells L-1). During the rainy season, there are only two classes of phytoplankton, namely Bacilariophyceae and Chlorophyceae. During the dry season, there are three classes of phytoplankton, namely Bacilariophyceae, Chlorophyceae and Cyanophyceae class. The plankton diversity index at the pollution site in Bison Karanganyar village was lower (H=1.47) than in the upstream location, namely Bendung Colo Sukoharjo village (H=2.1).