Phytoplankton of two river lakes in relation to flooding period (River Bug, Eastern Poland)

Studies were carrying out in two shallow (mean depth approximate to 0.3 m) and small (area 2.7-8.2 ha) river lakes, which were flooded bywater of River Bug (Eastern Poland) once a year (in spring). The species composition, biomass of phytoplankton and concentration of chlorophyll a were studied. Samples were taken in June (after flooding) and in August (after three months of isolation from river water). About 150 species of phytoplankton were determined. After the flood period phytoplankton biomass was dominated by nannoplankton belonging to Cryptophyceae and Chrysophyceae (strategy-r) and in the stabilization period by microplanktonic green and blue-green algae (strategy-K). The higher biomass and concentration of chlorophyll a values were noted in August than in June. The differentiation of phytoplankton was also stated between near-by stations in both lakes.