Seasonal Assessment of Physico- Chemical Parameters, Phytoplanktons Composition and Abundance in Ajiwa Reservoir, Katsina State, Nigeria

Abstract

Anthropogenic activities, climatic changes, and dam geology have been reported to influence the productivity of reservoirs. This study aimed to determine the seasonal variability of physico-chemical parameters, phytoplankton composition, and abundance in Ajiwa Reservoir, Katsina State, Nigeria. Water samples were collected from December 2022 to September 2023 and analyzed for phytoplankton composition and physico-chemical conditions using standard methods. The results revealed that the mean water temperature (25.12±3.76оC), pH (7.03±0.55), dissolved oxygen (6.84±0.75mg/L), biochemical oxygen demand (3.00±0.79mg/L), electrical conductivity (119.67±14.40μЅ/cm), total dissolved solids (16.55±4.80mg/L), turbidity (100.47±14.56NTU), water hardness (86.46±4.93mg/L), nitrate-nitrogen (7.91±2.69mg/L), and phosphate-phosphorus (5.43±2.40mg/L) were significantly different across seasons (P < 0.05). The percentage compositions of phytoplankton were Chlorophyceae (33.50%), Bacillariophyceae (22.36%), Cyanophyceae (12.57%), Cryptophyceae (12.48%), Euglenophyceae (6.58%), and Dinophyceae (4.55%) from four sampling sites during the study period. Phytoplankton were found to be more abundant in the wet season (858) than the dry season (327). The correlation matrix showed significant correlations between phytoplankton and physicochemical parameters. The compositions of phytoplankton in the reservoir were affected by seasonal variations and fluctuations in physicochemical parameters.