Microplastics plastisphere is an important eco-site for nitrous oxide emission in lakes: A case study of various lakes in Wuhan, China

This study used correlation analyses to examine the microbial mechanisms linking microplastics and nitrous oxide (N2O) fluxes in 18 typical lakes in Wuhan city. The microplastic abundances were 502 ± 212 items/m3 in the surface water and 305 ± 216 items/kg in dry sediments. The microplastics were predominantly black and fiber shaped in both surface water and sediments. The N2O flux was positively correlated with total phosphorus (p < 0.01), suspended particles (p < 0.01), total nitrogen (p < 0.05), and dissolved inorganic nitrogen (p < 0.01) in surface water. nirK/nosZ I was negatively correlated with the N2O flux and positively correlated with dissolved N2O concentration in surface water (p < 0.05). The microplastic abundance in surface water was positively correlated with nosZ II in water (p < 0.01) and nirK/nosZ I in sediment (p < 0.001). The microplastics in sediments were negatively correlated with nirK/nosZ I in water (p < 0.001) and positively correlated with nirS in sediment (p < 0.05). The predominant plastisphere denitrifiers in this study were nirS-type in sediments and nirK-type in surface water. The predominant denitrifier in surface water was Flavobacterium, where it had far higher relative abundances compared to sediments. The co-occurrence network between nitrifiers, denitrifiers, and water quality indexes implied that denitrifiers competed strongly in sediments, while they cooperated in surface water. Looking at the whole microbial community, the competitive and cooperative relationships were more complex in the sediment samples. The N2O flux was positively correlated with the plastic degradation function in sediment (p < 0.05), implying the plastisphere was a significant contributor. Microplastics in lakes, i.e., the plastisphere, may be a novel microbial colonization site that could be vital to ecosystem N2O emissions.