Response of denitrifying anaerobic methane oxidation processes in freshwater and marine sediments to polyvinyl...

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) plays a crucial role in mitigating methane (CH₄) in natural environments. The increasing presence of microplastics (MPs) in these environments due to human activities is a growing concern. However, the impact of MPs on n-DAMO microorganisms and their role in greenhouse gas regulation, particularly CH₄ reduction, remains unclear. This study investigates the effects of polyvinyl chloride (PVC) MPs on n-DAMO activity and the associated microbial communities in freshwater and marine sediments at varying concentrations of (R0/M0-no addition, R1/M1-0.5 %, R2/M2-2%). The results showed that the presence of MPs significantly increased the n-DAMO rate (2.89-3.58 nmol ¹³CO₂ g^-1 d^-1) compared to the control groups (R0: 1.29 nmol ¹³CO₂ g^-1 d^-1, M0: 0.11 nmol ¹³CO₂ g^-1 d^-1), with marine sediments showing a more pronounced response. Additionally, the proportional contribution of nitrate-DAMO processes increased following MP exposure. The presence of PVC MPs also altered the microbial diversity of n-DAMO. Upon the addition of MPs, the microbial community composition of n-DAMO in marine sediments changed more significantly. This study provides the first evidence of a positive impact of PVC MPs on n-DAMO processes, suggesting that the presence of PVC MPs in sediments could potentially contribute to the reduction of CH₄ emissions.