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Polymer-specific microplastic risks and microbial community shifts in a freshwater ecosystem: Field evidence from the Hunter River, Australia
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Researchers conducted a snapshot survey of microplastic contamination across five sites in the Hunter River, Australia, finding concentrations up to 229 particles per liter, with polyethylene, PET, and polyamide dominating, and three sites reaching the highest hazard level on the Polymer Risk Index.
Microplastics (MPs) are an emerging concern in freshwater ecosystems due to their role in transporting pollutants and altering microbial dynamics. This study provides a snapshot of MP contamination, ecological risks, and associated microbial communities in the Hunter River, Australia, based on single-time-point sampling across five sites. MP concentrations ranged from 47 to 229 ± 42.63 particles L-1, with fibres, white particles, and 100-200 μm fragments most abundant. Polyethylene (PE), polyethylene terephthalate (PET), and polyamide (PA) were dominant polymers, while Omadale, Aberdeen, and Wollombi were rated hazard level V on the Polymer Risk Index due to high levels of polyvinyl chloride (PVC) and polycarbonate (PC). Microbial profiling revealed significant site-specific differences in diversity and composition, with higher Chao1 and Shannon indices at Aberdeen and Denman. Actinobacteria, Proteobacteria, Cyanobacteria, and Chloroflexi dominated across sites, though their relative abundances varied. Nineteen plastic-degrading genera were identified from PlasticDB, including Sphingomonas, Pseudoxanthomonas, Rhodococcus, and Microbacterium, alongside predicted functional enzymes involved in the degradation of xenobiotics and plastics. Canonical correspondence analysis (CCA) linked specific polymers (PVC, PET, PC, PS) to microbial taxa, including Kapabacteria, Parcubacteria, and Actinobacteria. Co-occurrence networks of plastic degraders showed distinct structural differences, with Aberdeen hosting the most complex network and Singleton the sparsest, suggesting that local conditions influence microbial stability and degradation potential. Broader network analyses revealed that higher MP loads were associated with reduced modularity and increased fragmentation, indicating disrupted community cohesion. Indicator species analysis further identified site-specific taxa, emphasizing environmental drivers of community structure. Overall, these findings demonstrate that MPs pose ecological risks not only through their abundance but also via polymer-specific effects on microbial assembly. This study provides essential baseline data for Australian rivers, supporting targeted monitoring and management strategies to mitigate polymer-driven ecological impacts.
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Researchers assessed microplastic contamination across water, sediment, and seven native fish species in the Indian stretch of the Brahmaputra River, finding water concentrations of 140–420 particles/m³ and sediment loads of 13–53 particles/kg, with polymer hazard indices reaching the highest risk category at multiple sites due to polyurethane and PVC particles—providing the first ecological risk baseline for this major Himalayan river.
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Researchers aggregated data from 2,474 microplastic samples across 165 publications to assess ecological risk in Chinese rivers, finding widespread contamination with average abundance varying substantially by watershed characteristics. A revised risk assessment accounting for particle morphology and polymer toxicity raised concern levels beyond previous estimates.
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Researchers conducted a comprehensive review of microplastic occurrence in freshwater ecosystems and performed the first probabilistic environmental risk assessment for specific polymer types. They established predicted no-effect concentration values for polystyrene and polyethylene and calculated risk quotients suggesting that current microplastic levels in most freshwater environments pose a low ecological risk.
Quantifying environmental emissions of microplastics from urban rivers in Melbourne, Australia
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Researchers quantified microplastic pollution in four Melbourne rivers flowing into Port Phillip Bay, finding an average of 9 microplastics per liter with polyamide and polypropylene among the most common polymers detected across all sampling sites.
Characteristics, Contamination Levels, and Ecosystem Risk Assessment of Microplastics in Surface Water of a Highly Urbanized River from a Developing Country
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Researchers characterized microplastic contamination in an urban river near a megacity in a developing country, finding concentrations of 350 to 660 particles per cubic meter of water. Polyethylene and polypropylene from household and municipal waste were the most common types, and a risk assessment found concerning contamination levels at several sampling sites. The study highlights how rivers in developing nations can serve as major pathways for microplastics to reach the ocean and enter the food chain.
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