Effects of physico-chemical parameters on the composition and abundance of phytoplankton in Ajiwa Reservoir Katsina State, north western Nigeria

Studies on the effects of physico-chemical parameters on the composition and abundance of phytoplanktonin Ajiwa reservoir was carried out from September, 2014 to August, 2015. Five sampling stations were chosen; the physico-chemical parameters and phytoplanktonspecies were determined using standard methods, procedures and instruments. Nineteen physicochemical parameters were determined. Some of their mean value are; Water Temperature (24.05±0.38C), Turbidity (98.0±2.28NTU), TDS (70.68±2.71mg/l), Electrical Conductivity (158.55±3.04µS/cm), Total Hardness (87.16±2.37mg/l), D.O (4.10±0.13mg/l), Calcium (40.34±1.35mg/l) and Nitrate- Nitrogen (1.07±0.08mg/l). The result also indicated the presence of 40 species of phytoplankton belonging to 5 major classes, viz: Chlorophyceae , Bacillariophyceae , Cyanophyceae , Dinophyceae and Euglenophyceae . The dominant phytoplankton was the Chlorophyceae (40.13%), followed in order by Bacillariophyceae (23.94%), Cyanophyceae (19.98%), Euglenophyceae (8.41%) and Dinophyceae (7.58%). Indices of general diversity (H), evenness (E), dominance and relative abundance were in the following order of increasing magnitude station 5 > station 1 > station 4 > station 2 and > station 3 respectively. Canonical correspondence analysis (CCA) was carried out to analyse the relationship between the physico-chemical parameters and the phytoplankton. It showed that the most important factors affecting the phytoplankton distribution are water temperature, DO, NO 3- N, PO 4- P, pH, TDS and turbidity.The fluctuation of the physicochemical parameters and phytoplankton species of the reservoir could be attributed to high influx of nutrient into the reservoir as a result of farming activities, cattle rearing, bush burning and bathing within the vicinity of the reservoir. Monitoring of human activities within the immediate catchment area of the reservoir and education on wise use of the water is recommended. Keywords: Abundance,  Composition, CCA, Physico-chemical,  Phytoplankton,Reservoir