Distribution and Diversity of Bacteria in a Small Tropical Freshwater Body (Aiba Reservoir) in Iwo, Osun State, Nigeria.

Abstract

Environmentalists have become increasingly concerned about the pollution of surface waters. The Aiba reservoir is the second oldest impoundment of Osun river basin and provides potable water to Iwo community. The diversity of bacteria in the Aiba Reservoir was studied by collecting water samples from four locations within the reservoir to reflect human impacts during three different seasons. The most probable number (MPN) of bacteria at the different sampling locations during the sampling seasons, the total non-specific bacteria count, total coliform and Escherichia coli count were measured using the tube dilution and pour plate techniques. Significant differences were observed in various parameters of bacterial diversity. Water samples from all sampling points were contaminated with coliforms, the highest being 1100+ MPN/100ml in location D. the highest number of bacteria was isolated in June at all sampling locations. Seventy-nine bacteria belonging to sixteen genera and twenty-three species were isolated. The genus Bacillus was the most diverse with thirty-one isolates and eight species. Other genera isolated were Aeromonas, Citrobacter, Listeria, Proteus, Escherichia, Klebsiella, Alcaligenes, Enterobacter, Corynebacterium, Lactobacillus, Edwardsiella, Flavobacterium, Staphylococcus, Streptococcus and Acinetobacter. Of the 23 genera isolated 10 (43.5%) were Gram negative bacteria, 60% of which are coliform bacteria. Eight (61.5%) of the Gram positive bacteria belonged to the Genus Bacillus. The high bacteria count and the type/genera of bacteria isolated are indicative of contamination of the system with soil from agricultural runoff, domestic sewage and fish remains. This on the long run could lead to spread of infective diseases to the populace.