Microplastics and Microbial Contamination in Warri River Surface Waters, Delta State, Nigeria

Abstract

The increasing accumulation of microplastics and microbial contaminants in surface waters has emerged as a significant environmental and public health concern, particularly in regions characterised by inadequate waste management practices, such as the Niger Delta, Nigeria. This study investigated the occurrence, characteristics and associated microbial contamination of microplastics in the surface waters of the Warri River, Delta State, Nigeria. Water samples were collected from five locations along the river and analysed using stereomicroscopy to characterise microplastics based on shape, size and colour. Phthalate esters were quantified using gas chromatography–mass spectrometry (GC–MS), while microbial analyses involved the enumeration and identification of total heterotrophic bacteria, coliforms and fungi using standard microbiological procedures. Microplastics were detected at all sampling locations, with fibres and filaments constituting the predominant particle types. The most abundant size fractions were 0.3–0.1 mm and 1–0.3 mm, indicating extensive fragmentation of larger plastic debris. Black, brown and transparent particles were the most frequently observed colours, suggesting inputs from domestic activities and degraded plastic materials. GC–MS analysis confirmed the presence of phthalate esters, indicating the occurrence of plastic-associated chemical contaminants within the aquatic environment. Total heterotrophic bacterial counts ranged from 5.24 × 10⁶ to 9.10 × 10⁶ CFU mL⁻¹, total coliform counts ranged from 90 to 270 MPN 100 mL⁻¹, and total fungal counts ranged from 2.60 × 10³ to 4.90 × 10³ CFU mL⁻¹ across the sampling locations. Identified microbial isolates included Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Aspergillus spp. and Candida spp., many of which have been reported to possess enzymatic capabilities associated with the degradation of plastic polymers. The findings demonstrate that the Warri River is affected by both microplastic pollution and elevated microbial contamination, posing potential ecological and public health risks to aquatic ecosystems and communities that depend on the river. Strengthening waste management systems, improving wastewater treatment infrastructure and implementing routine environmental monitoring are recommended to mitigate pollution and safeguard environmental quality.