Effects of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) biodegradable microplastics on the abundance and diversity of denitrifying and anammox bacteria in freshwater sediment

• Published in: Environmental pollution (1987) Vol. 315; p. 120343
• Main Authors: Nie, Zhenpeng, Wang, Lulu, Lin, Yanxu, Xiao, Naidong, Zhao, Jianwei, Wan, Xiaoqiong, Hu, Jinlong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.12.2022
• Subjects: Anammox bacteria; Denitrifying bacteria; Freshwater sediment; PBAT microplastics; PLA microplastics; Denitrifying bacteria; PLA microplastics; Anammox bacteria; PBAT microplastics; Freshwater sediment
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.120343

Microplastics (MPs) have been widely distributed on Earth and have drawn global concern for freshwater and marine ecosystems. Biodegradable plastics have risen in popularity to replace nonbiodegradable plastics all over the world. The effects of biodegradable plastics on denitrifying and anammox bacteria in freshwater sediment remain largely unknown. In this study, water column reactors containing polylactic acid (PLA) or polybutylene adipate-co-terephthalate (PBAT) MPs in sediment were established to simulate lake ecosystems and analyze the effects of biodegradable MPs on sedimentary nitrogen transformation microorganisms. The total organic carbon (TOC) concentrations in the PLA and PBAT groups were slightly higher than those in the control group, which might be related to the slow degradation of these two plastics. Denitrifying and anammox bacterial diversities decreased after adding MPs to sediments for 30 days, and the dominant OTUs of these two bacteria were differentiated from the control. The abundance levels of nirS denitrifying and anammox bacteria on the PLA MP surface were significantly higher than those in the other groups (P < 0.05), but they were lower in the PBAT groups than in the other groups. As an excellent electron donor for the denitrification process, lactic acid release from PLA degradation resulted in the enrichment of denitrifying and anammox bacteria on the MP surfaces. However, PBAT led to various responses of bacteria in an anaerobic environment. In addition, the redundancy analysis results indicated that total phosphorus, TOC and nitrate were strongly negatively correlated with the abundance levels of denitrifying and anammox bacteria. Our findings provided insight into the effects of MPs, especially the biodegradable ones, on sedimentary nitrogen-transformation bacteria. [Display omitted] •PBAT decreased the abundances of nirS denitrifying and anammox bacteria.•Denitrifying and anammox bacteria exhibited the highest abundances on PLA surface.•Biodegradable microplastics (MPs) decreased alpha diversities of these bacteria.•Dominant OTUs of these bacteria on MPs surface differentiated in different directions.•Nitrate was negatively correlated with the abundances of these bacteria.