The co-presence of polystyrene nanoplastics and ofloxacin demonstrates joint effects on structure, assembly, and metabolic activities of marine microbial community

Nanoplastics (NP) is one of the most wide-spread and hazardous litter and can adsorb organic pollutants (e.g., antibiotics) and heavy metals, which may aggravate toxic effects on various organisms. Ofloxacin (OFL) is a common-used antibiotics that dramatically increased in environments. The combined effects of NP and OFL on planktonic/benthic microbial community structures, assembly, networks, and the shifts in prokaryotic metabolic activities, are still largely unknown. In the current study, we investigate the combined effects of polystyrene nanoplastics and ofloxacin on planktonic/benthic microbial communities using integrated methods. The results demonstrate that the co-presence of NP and OFL have effects on prokaryotic community structures and component abundance, while the effects on eukaryotic communities are not significant, which may be due to the multicellular structure for protection and higher mobility. The co-presence of NP and OFL also: (1) shrinks the niche breadths of planktonic prokaryotes and benthic eukaryotes, (2) simplifies the composition and ecological functions of co-occurrence networks via decreasing nodes, edges and modules of networks, and (3) impacts the network stability. In addition, it has been revealed that under high concentration of both NP and OFL, much more differential prokaryotic pathways are induced, indicating their combined effects on the metabolic activities. This work provides a better understanding of the current less-known combined effects of polystyrene NP and OFL on marine microbial communities.