Effects of Glyphosate and Butachlor Herbicides Concentrations on Resident Culturable Bacterial Populations from Surface Water Sources in Makurdi: A Microcosm Study

Abstract

The effect of different concentrations of herbicides on bacterial isolates from various surface water sources was undertaken. The research was aimed at the isolation, identification and characterization of bacteria from selected surface water sources, in order to ascertain the effects of varying concentrations of herbicides on resident bacterial populations. Samples were obtained from five different surface water sources and sediments in Makurdi, using sterilized plastic containers. The herbicides used were Butachlor and Glyphosphate ammonium salt with Rid-over’s trade name (500, 250, 125, 62.5 and 31.5 mg). Both herbicides were spiked in the volume of water samples to reflect the recommendation of the manufacturer). The bacteriological analysis of the samples prior to spiking with the herbicides indicated that, Afuko stream had the highest total heterotrophic bacteria (THB) count of 4.55x107cfu/mL; River Benue 3.45x107cfu / mL; Akighir stream 3.0x107cfu / mL; whereas Mu river and Jamu stream had the lowest total heterotrophic bacteria count of 2.36x107cfu / mL and 2.31x107cfu/mL respectively. The isolates from the water sources in the order of highest percentage occurrences included; Escherichia coli 24(21.7%); Bacillus sp 22(21.2%); Salmonella sp 20(17.6%); Pseudomonas sp 17(15.0%); Proteus sp 16(14.1%) and Staphylococcus aureus 14 (12.3%) before spiking with the herbicides. The number of bacteria colonies increased as the days increased after spiking at different concentrations of the herbicides though colony counts were higher at lower concentrations than higher concentrations. The bacteria isolates have shown resistance to herbicides, which implies biogenic elements for their physiological processes.