Composition and Seasonal Variation in Planktonic Blue-green Algae in Shadawanka River, Bauchi, Nigeria

The study of the composition of Planktonic blue-green algae was under taken for the period of eight months (February-September, 2007). Assessment of physicochemical characteristics of the river was also attempted to find out the state of the water quality of the river. Twenty four species of blue-green algae were observed belonging to two orders namely: the Chroococcales and the Nostocales. The chroococcales were sparsely represented by genera of Oscillatoria and Pleurotenuim. Oscillatoria dominated the order with a higher specie relative abundance and composition. Common most abundant species observed include: Anabaena, Calothrix, Microcystis and Oscillatoria. The River is well oxygenated (DO>9.8mg/L) and is Characterised by moderate nutrient levels, high electrical conductivity (>204 ^mScm" ʹ) and low BOD (2.1-6.4mg/L). pH was circumneutral, having three regimes, this attest that the water is not polluted and can support other forms of aquatic life. Variation in the composition of the algae and physicochemical characteristics of the river was attributed to change in season with respect to rainfall, solar radiation anthropogenic activities and inflow of sediments silts.