Phytoplankton diversity and abundance as a function of water quality for fish production: a case study of two man-made Reservoirs in Zaria, Nigeria

Water quality and phytoplankton composition of two Reservoirs (Bomo and Kubanni) in Zaria, Nigeria, were investigated for their fish production potentials from April to June 2011. April represented the dry period, while May and June were months with rains. Physicochemical parameters of the two Reservoirs showed significantly different (p < 0.05) characteristics. Nutrient concentrations were higher in Bomo Reservoir than those obtained in Kubanni Reservoir during the study period. A total number of 46 and 20 phytoplankton species belonging to Chlorophyceae, Bacillariophyceae, Cyanophyceae and Euglenophyceae were recorded in Bomo and Kubanni Reservoirs, respectively. Relative abundance (RA) of Chlorophyceae in Bomo Reservoir was 50.1% and 63.7% in April and May, respectively. However, in Kubanni Reservoir 83.3% RA of Bacillariophyceae was obtained in April and 71% of Cyanophyceae in May. Community structure analyses showed a higher diversity and species richness in Bomo Reservoir than Kubanni Reservoir during the study period. A significant correlation was obtained between most physicochemical parameters analyzed with the occurrence and abundance of several phytoplankton species. The high species diversity obtained especially of phytoplankton groups other than the cyanobacteria in Bomo Reservoir shows that Bomo Reservoir will be very suitable for sustainable fisheries production compared to Kubanni Reservoir with fewer species and as much as 71% RA of cyanobacteria in May. However, there is the need to control the irrigational farming activities around the Bomo Reservoir and also to prevent the discharge of domestic effluents into it. Key words : Microalgae, Cyanobacteria, community structure, physicochemical parameters, Aquaculture