Seasonal Diversity and Abundance of Phytoplankton Influenced by Physicochemical Parameters in the Lower River Benue, Nigeria

Abstract

This study investigates the seasonal diversity and abundance of phytoplankton in the Lower River Benue, influenced by various physicochemical parameters. The research was conducted over an 18-month period, from January 2020 to June 2021, across three sampling sites: Lau, Mayo-Ranewo, and Ibi. Phytoplankton samples were collected monthly, covering both dry and wet seasons, and analyzed for diversity and abundance. Concurrently, water quality parameters such as temperature, pH, turbidity, electrical conductivity, total dissolved solids (TDS), dissolved oxygen (DO), biochemical oxygen demand (BOD), hardness, fluoride, and nitrate were measured. The results indicated significant seasonal variations in phytoplankton distribution, with higher abundance during the wet season due to increased water flow and nutrient input from runoff. Key species identified included Microcystis flos-aquae, Euglena gracilis, and Spirogyra sp., which collectively contributed to nearly half of the total phytoplankton abundance. The study also revealed that physicochemical parameters such as temperature, pH, and nutrient concentrations directly influenced phytoplankton diversity and abundance. Principal Component Analysis (PCA) highlighted the correlations between environmental parameters and phytoplankton distribution, showing that temperature negatively correlated with turbidity and nitrate, while BOD had a significant negative correlation with fluoride and nitrate. This research provides valuable insights into the ecological processes governing the Lower River Benue and underscores the importance of monitoring water quality to develop effective water resource management strategies.