Abstract
Macroplastic pollution in freshwater systems is an increasing environmental concern due to its persistence, widespread distribution, and potential role in supporting microbial colonisation. Whilst previous studies have demonstrated that plastics can function as substrates for microbial biofilm formation, limited research has investigated the role of macroplastics as potential transport mechanisms for bacteriological contamination within South African freshwater systems. This study therefore aimed to assess macroplastics as a novel potential carrier for bacteriological contamination in the Jukskei River, Gauteng, South Africa.
This study employed a cross-sectional quantitative design to investigate macroplastic-associated bacterial communities within the Jukskei River. Macroplastic debris was collected from the Jukskei River over four sampling campaigns conducted between January and February 2025 using a manually deployed plastic capture net. Collected plastics were categorised according to polymer type and deterioration status. Swab samples were obtained from representative macroplastic surfaces and analysed using shotgun metagenomic Next-Generation Sequencing to characterise associated microbial communities and identify potentially pathogenic bacterial taxa.
A total of 210 macroplastic items were collected, with polystyrene (PS) (59.0%) and low-density polyethylene (LDPE) (24.3%) identified as the dominant polymer types. Most plastics (69.5%) exhibited visible deterioration, with a statistically significant association observed between plastic type and deterioration status (χ²(6, N = 210) = 72.19, p < .001). Metagenomic analysis revealed bacterial dominance across all samples, with Proteobacteria identified as the most abundant bacterial phylum. Multiple clinically relevant and World Health Organisation (WHO) priority bacterial taxa were detected on macroplastic debris, including carbapenem-resistant Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and resistant Enterobacterales.
The findings of this study contribute to the limited body of South African research investigating plastisphere-associated microbial communities within urban freshwater systems. The study supports the potential role of macroplastic debris as environmental substrates capable of supporting bacterial persistence and possible transport interfaces for bacteriological contamination within polluted freshwater environments. These findings highlight the importance of addressing macroplastic pollution not only as an environmental issue, but also as a potential Environmental Health concern requiring integrated waste management, environmental monitoring, and public health interventions.