Assessment of limnological variables and algal diversity of Shagari Reservoir, Sokoto, Nigeria

Abstract

Shagari Reservoir is the second man-made lake in Sokoto, impounded in 2007 to improve irrigation activities, provide drinking water and control flood. The study was conducted from June to October 2014. The aim was to determine the level of limnological variables at two depths (0.5m and 1m) and to survey diversity of algal species in the reservoir. Among the physicochemical variables studied, temperature was slightly higher at 0.5 m than at 1 metre depth. Phosphate concentration tends to be higher at 1 meter depth. Nineteen (19) species of algae belonging to five divisions were identified, in which Euglena viridis accounted for 20.57%. The algal assemblage was found to comprise of Euglenophyta (30.03%) > Chlorophyta (27.43%) > Bacillariophyta (22.27%) > Dinophyta (12.06%) > Cyanophyta (7.8%). July seem to have equal (Equitability Index) distribution of these algal species compared to other months of study and the months varied in terms of richness and evenness. Status of the lake suggests that the nutrient load was low, though enough to promote the growth of algal species and little anthropogenic activities/influences were observed within the reservoir. Proper monitoring and management is required to protect the reservoir from excessive input of nutrients that could lead to eutrophication.

Keywords: Algae, Euglena viridis; limnological; variables; Shagari Reservoir