Polyethylene microplastic-induced microbial shifts affected greenhouse gas emissions during litter decomposition in coastal wetland sediments

Microplastic contamination has become increasingly aggravated in coastal environments, further affecting biogeochemical processes involved with microbial community shifts. As a key biogeochemical process mainly driven by microbiota in coastal wetland sediments, litter decomposition contributes greatly to the global greenhouse gas (GHG) budget. However, under microplastic pollution, the relationship between microbial alterations and GHG emissions during litter decomposition in coastal wetlands remains largely unknown. Here, we explored the microbial mechanism by which polyethylene microplastic (PE-MP) influenced greenhouse gas (i.e., CH, CO and NO) emissions during litter decomposition in coastal sediments through a 75-day microcosm experiment. During litter decomposition, PE-MP exposure significantly decreased cumulative CH and CO emissions by 41.07% and 25.79%, respectively. However, there was no significant change in cumulative NO emissions under PE-MP exposure. The bacterial, archaeal, and fungal communities in sediments exhibited varied responses to PE-MP exposure over time, as reflected by the altered structure and changed functional groups of the microbiota. The altered microbial functional groups ascribed to PE-MP exposure and sediment property changes might contribute to suppressing CH and CO emissions during litter decomposition. This study yielded valuable information regarding the effects of PE-MP on GHG emissions during litter decomposition in coastal wetland sediments.