Spatial variation in bacterial community structure and pollution response in river sediment

Rivers are unique ecosystems where pollution frequently occurs, altering the biogeochemical characteristics of both water bodies and sediments. However, little is known about the effects of human activities on the lower course of River Ogun. This study assessed the association between anthropogenic activities and sediment bacterial communities at the time of sampling by comparing sediment physicochemical properties and the bacterial community structures of samples. Samples were taken from four distinct sites along the lower course of the river. Bacterial community structure of these sites was investigated using the 16S rRNA gene PacBio sequencing. Total polycyclic aromatic hydrocarbons (PAHs) were lowest at Location B (6.95 mg/kg) and highest at Location A (15.6 mg/kg). The dominant bacterial phyla in the sediments were Pseudomonadota, Bacillota, Bacteroidota and Actinomycetota. A notable abundance of Thauera was observed across all the locations, particularly at Location A, and Psychrobacter known for plastic degradation was detected exclusively at this site. Among all the sites, Location A exhibited the lowest bacterial diversity, as indicated by both species' richness and evenness, where the Thauera selenatis group and Psychrobacter maritimus were dominant. Location B exhibited the highest bacterial diversity, Location C and D displayed intermediate diversity, sharing a 40% similarity index. Environmental variables that significantly explained beta diversity patterns included pH, anthracene and fluoranthene. This study provides insights into bacterial metagenomes of a freshwater inundated with plastics, heavy metals and consortium of persistent organic compounds. The findings highlight the value of integrating metagenomic and physicochemical analyses to identify correlations that help explain the key drivers shaping ecosystem dynamics.