Assessments of the impacts of chemical and hydrocarbon pollution on Ologe Lagoon water and its prokaryotic community structure

Abstract

Ologe Lagoon, in Lagos State Nigeria, is one of the freshwaters exposed to chemical and hydrocarbon pollution. The impacts of anthropogenic pollution on lagoon microbial communities were assessed. Three sampling points were identified, namely Ologe industrial contaminated water (OLICW), Ologe human activity water (OLHAW), and relatively undisturbed water (OLPW). The microbial community structure of samples was determined via Illumina shotgun next-generation sequencing, while taxonomic classification was done by centrifuge. Acidic pH of (3.8 ± 0.02; 4.6 ± 0.01; and 6.5 ± 0.04) were observed for OLHAW, OLICW and OLPW. The heavy metals nickel and lead showed increase at OLICW > OLPW > OLHAW with their values higher than the WHO permissible limit. The gas chromatography flame ionization detector (GC-FID) fingerprints of the samples showed presence of aliphatic (nC₁-nC₁₇) and aromatic hydrocarbons like pyrene, anthracene, phenanthraquinone, and phenanthridine which is evidence of pollution. Structurally, the water metagenomes comprised of 40, 43, and 42 phyla, 67, 74, and 72 classes, 666, 982, and 920 genera from OLHAW, OLICW, and OLPW metagenomes. Dominant phyla across the three sites were Proteobacteria (37.1–64.1%), Actinobacteria (6.1–21.6%), Cyanobacteria (5.3–14.0%), Planctomycetes (6.6%), Firmicutes (6.6–5.7%). Archaea phyla like Euryarchaeota and Creanarchaeota were encountered. Principal component ordination (PCO) showed that OLHAW prokaryotic community had total variance of 88.2% PCO1 separating it from OLICW and OLPW, also OLICW and OLPW were separated by PCO2 accounting for 11.8% variation but clustered showing 60% similarity. The study showed abundance of Cyanobacteria, Nitrospira and Clostridia which are biological indicator of pollution and their presence signify eutrophication.