Nitrogen metabolic responses of non-rhizosphere and rhizosphere microbial communities in constructed wetlands under nanoplastics disturbance

Abstract

Constructed wetlands (CWs) serve as crucial sinks for nanoplastics, making them a significant research hotspot regarding the impacts of nanoplastics on the nitrogen metabolism within microbial communities. However, there has been a lack of comparative analysis between rhizosphere and non-rhizosphere microbial communities under nanoplastics disturbance. This study analyzes the nitrogen metabolic responses of these microbial communities in CWs following repeated nanoplastics disturbance. Results indicated that repeated nanoplastics disturbances led to a 17.72 % decrease in the relative abundance of nitrifying bacteria in rhizosphere microbial community, while the relative abundance of Polaromonas increased by 5.24 % in non-rhizosphere community. Microbial network revealed that rhizosphere microbial community primarily contributed to nitrogen metabolism by forming a tightly connected network. In contrast, non-rhizosphere microbes dominated nitrogen cycling by promoting energy and information exchange among microbes. Furthermore, rhizosphere and non-rhizosphere microbial communities exhibited distinct resistance and adaptation to nanoplastics disturbance. Rhizosphere microbes responded by activating antioxidant systems, whereas non-rhizosphere microbes could develop adaptive growth and metabolism, using nanoplastics as a carbon source. The adaptation strategies of non-rhizosphere community proved more advantageous for coping with persistent nanoplastics disturbance. This study comprehensively investigated the differences of nitrogen metabolism between rhizosphere and non-rhizosphere microorganisms in CWs under nanoplastics disturbance.

Keywords: Constructed wetland; Nanoplastics; Nitrogen metabolism; Non-rhizosphere microbes; Rhizosphere microbes.