Typical pathogens on plastic debris in downstream of Sai Gon and Dong Nai rivers: an initial observation

Plastic pollution is recently receiving significant attention. In aquatic ecosystem, plastic debris can provide a habitat for microbial communities, including pathogens which might cause ad-verse impacts on aquatic animals and human health. This study, for the first time, investigated densities of typical pathogens of Coliforms and Vibrio spp. associated on plastic samples col-lected in surface water (SW), water column (WC, 5 m below surface water), and sediment (SED) at downstreams of Sai Gon river (Phu My bridge site) and Dong Nai river (Binh Khanh habour site) in the dry season of 2022. The results showed that densities of pathogens associat-ed on SW plastics were significantly higher than densities of pathogens associated on WC and SED plastics. For instance, (i) densities of Coliform on SW plastics (9.7 ± 0.1 × 106 and 180.0 ± 10.0 × 106 CFU/g plastic) were significantly higher than the ones on WC plastics (3.1 ± 0.5 × 106 and 5.5 ± 1.2 × 106 CFU/g plastic), and the ones on SED plastics (1.7 ± 0.3 × 106 and 5.7 ± 0.7 × 106 CFU/g plastic); and similarly (ii) densities of Vibrio spp. on SW plastics (4.2 ± 0.1 × 104 and 1.3 ± 0.2 × 105 CFU/g plastic) were significantly higher than the ones on WC plastics of 0.0 ± 0.0 and 7.7 ± 0.4 × 103 CFU/g plastic, and the ones on SED plastics of 2.0 ± 0.2 × 104 and 4.4 ± 0.0 × 104 CFU/g plastic, in Phu My and Binh Khanh, respectively. Other hand, densi-ties of pathogens on plastic samples colleceted in Phu My were significally lower than in the ones collected in Binh Khanh. These findings proposed that pathogen contamination on the plastic debris in downstream area is likely heavier than in upstream area of Sai Gon and Dong Nai rivers.