Microplastics as carbon-nutrient sources and shaper for microbial communities in stagnant water

Highlights: • The nutrient-supply effect of microplastics for bacterial growth was explored. • Different MPs contribute various assimilable organic carbon formation and subsequently shaped microbial communities. • MPs' properties have impacts on bacterial growth and distribution between biofilm and water phase. • Biofilm formatting and formatted phases of biofilm, were defined and simulated. Microplastics (MPs) are emerging pollutants as vectors for microbial colonization, but their role as nutrients sources for microbial communities has rarely been reported. This study explored the impact of six types of MPs on assimilable organic carbon (AOC) and microbial communities over eight weeks. The following were the primary conclusions: (1) MPs contributed to AOC increment and subsequently increased bacterial regrowth potential. The maximum AOC reached 722.03 μg/L. The increase in AOC formation corresponded to AOC NOX, except in PVC samples where AOC P17 primarily increased. (2) The MPs accelerated bacterial growth and changed the bacterial distribution between the biofilm and water phases. A high MP surface-area-to-volume ratio or low MPs density contributed to bacterial accumulation and biofilm formation around the plastisphere, thereby decreasing the relative microbial proportion in the water phase. (3) High-throughput sequencing and scanning electron microscope revealed that different MPs shaped various microbial communities temporally and spatially. (4) Biofilm formatting and formatted models were established and simulated to explain the kinetic interaction between the AOC and bacteria inhabiting the plastisphere. Finally, the challenges that plastic-deprived AOC represent in terms of anti-bacterial measures and chemical safety are discussed.