Bacterial Community Profile and Phylogenetic Diversity of Water and Surface Sediments in Iko River Estuary, Akwa Ibom State- Nigeria

Abstract

A large amount of crude oil is spilled annually into the terrestrial and aquatic environments in Nigeria. This tends to upset the natural equilibrium of the marine environment as a microbial habitat. Thus, there is a need to evaluate the effect of exposure to crude oil on bacterial load and diversity using Iko River and Odoro Ikot pond as the study and pristine sites respectively. The bacterial isolates were molecularly identified using the 16S rRNA sequencing protocol. The total heterotrophic bacterial count (THBC) in the surface water (SW), sub-surface water (SSW) and sediment segments of Iko River ranged from 2.23±0.87 to 9.67 ± 0.43 x 106 CFU/ML while the THBC in the SW, SSW and sediment segments of the pristine site (Odoro Ikot pond) ranged from 1.87±0.53 to 4.8± 0.04x106 CFU/ML. The sediment had a significantly higher (P<0.05) THBC than the water segments (SW and SSW) in both Iko River and Odoro Ikot pond. The hydrocarbon utilizing bacteria (HUB) count in Odoro Ikot pond ranged from 0.40 ± 0.01 to 1.10 ± 0.03 x 106 CFU/ML while the HUB count in Iko River ranged from 0.53 ± 0.02 to 0.93 ± 0.04 x 106 CFU/ML, making Iko River have a higher number of total heterotrophic bacteria and hydrocarbon utilizing bacteria than Odoro Ikot pond. The Proteobacteria isolates had the highest bacterial diversity (77%) while members of the Firmicutes phylum had a 23% bacterial diversity. However, higher bacterial count and diversity were obtained from the sediment segment than from the water segments in both Iko River and Odoro Ikot pond implying that the sediment is more favourable for bacterial growth. Although the bacterial profile was affected by exposure to crude oil, there were variations in the phylogenetic diversities obtained from the different water segments attributable to crude oil concentration.