Pelagic and Benthic Plastisphere Show Differential Driving Effects on Nitrogen Cycle in Aquaculture Water

Plastisphere refers to biofilm forming on microplastics (MPs) surface, but the difference in microbial communities between pelagic and benthic plastisphere and their subsequent functions especially driving biogeochemical cycle is rarely studied. Here, MPs were incubated for 28 d in pelagic surface water and benthic water-sediment interface of aquaculture environments, respectively. The biofilm formation was stable after 21 d incubation and the amount of MPs-biofilm in benthic was higher than in pelagic environment. Moreover, richness and diversity of benthic plastisphere were higher than that of pelagic one. Also, a higher abundance of nitrogen-related bacteria ( Nitratireductor , Nitrosomonas and Nitrospira ) was observed in benthic plastisphere compared to pelagic MPs. The predominant Rhizobiales_bacterium containing amoA and amoB, assigned to M00528 (nitrification, ammonia→nitrite), showed high abundance in plastisphere especially that incubated in benthic environment, but more contribution of Desulfobacteraceae_bacterium encoding narG to M00528 was found in pelagic and benthic plastisphere. After 7-d microcosm incubation, plastisphere increased nitrate concentration and accelerated nitrification in pelagic system, but decreased nitrite concentration and inhibited nitrification in benthic system. These results indicate that pelagic and benthic plastisphere could show differential driving effects on nitrogen cycle in aquaculture water