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Trivalent iron (Fe3+)-dependent anaerobic oxidation of methane (Fe-AOM), which is mediated by metal-reducing bacteria, is widely recognized as a major sink for the greenhouse gas methane (CH 4), and is a key driver of the carbon (C) biogeochemical cycle. However, the effect of Fe3+ addition on AOM in the present investigation is still ambiguous, and the mechanism is vague. In this study, we investigated the mechanism of changes in AOM response to Fe3+ input at different wetlands by using laboratory incubation methods combined with molecular biology techniques. Results indicated that Fe3+ input did not always lead to promoted AOM rates, which may be mediated by complex environmental factors, while lower soil total nitrogen (TN) had a positive effect on the response of AOM subjected to Fe3+ input. Notably, the promoted response of AOM was regulated by higher soil microbial diversity, of which the Shannon index was a key indicator leading to variation in the AOM response. Additionally, several biomarkers, including Planctomycetota and Burkholderiaceae , were key microorganisms responsible for alterations in AOM response. Our results suggest that the capacity of Fe3+ cycling-mediated AOM may gradually decrease in light of increasing anthropogenic N and Fe inputs to global estuarine wetlands, while its reaction processes will become more complex and more strongly coupled with multiple environmental factors. This finding contributes to the enhanced understanding and prediction of the wetland CH 4 -related C with Fe cycles, as well as provides theoretical support for the underlying mechanisms. [Display omitted] • The mechanism of the change in the response to Fe3+ input by AOM was investigated. • Fe3+ input did not necessarily contribute to the AOM rate. • Lower soil TN content positively influenced the response of AOM. • Higher Shannon index has a positive effect on the response of AOM. • Planctomycetota , Burkholderiaceae , etc. caused variation in the response of AOM. [ABSTRACT FROM AUTHOR]

Due to poor management and the lack of environmental awareness, lots of masks (an emerging form of plastic pollution) are discarded into the environment during the COVID-19, thereby jeopardizing the health of humans and the environment. Our study introduces a novel perspective by examining the impact of physical damage on the microbial composition of masks in the water environment. We focus on the variations in biofilm formation on each layer of both damaged and undamaged masks, which allows us to understand more about the biofilm on each layer and the significant changes that occur when masks are physically damaged. Research has shown that the community structure of microorganisms on discarded masks can be altered in just ten days, showing an evolution from undifferentiated pioneer colonizing species ("non-picky") to adaptive dominant species ("picky"). Especially, considering that discarded masks were inevitably damaged, we found that the biomass on the damaged samples is 1.62–2.38 times higher than that of the undamaged samples, respectively. Moreover, the microbial community structure on it was also significantly different. Genes involved in biogeochemical cycles of nutrients are more enriched in damaged masks. When damaged, the colonization process and community structure in the middle layer significantly differ from those in the inner and outer layers and even enrich more pathogenic bacteria. Based on the above, it is evident that the environmental risk of masks cannot be assessed as a whole, and the middle layer carries a higher risk. [Display omitted] • Succession from undifferentiated pioneer colonized species to the adaptive dominant. • The biofilm on the middle layer was different from that on the other two layers. • When damaged, the middle layer enriched more pathogenic bacteria than the others. • The integrity of the masks plays a significant role in microbial colonization. • There is difference in biogeochemical cycling between damaged and undamaged masks. [ABSTRACT FROM AUTHOR]