Eukaryotic community succession on discarded face masks in the marine environment

Marine plastic exposure triggers rapid recruitment of plastic-degrading bacteria and accelerates polymer-specific transformations

Plastic pollution in marine ecosystems is a growing concern, yet the degradation behavior of different plastic types and their interactions with microbial communities remain poorly understood. This study investigated the degradation kinetics and microbial colonization of four widely used plastic materials, surgical masks (most made of PP), PET bottles, PS foam, and PP cups, over 40 days of seawater exposure in the Central Atlantic of Morocco. Mass loss measurement revealed distinct degradation patterns, with PS foam showing the highest mass loss (13 %), followed by PET bottles (5 %), likely due to environmental stressors that promote mechanical fragmentation. Surgical masks and PP cups exhibited minimal degradation, retaining nearly all their original mass, as well as limited extent of biodegradation. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) analyses showed the formation of oxidative functional groups on PP cups and significant structural changes in PS foam and PET, particularly in their crystalline structures, correlating with their higher mass reduction rates. SEM/EDX biofilm imaging confirmed extensive microbial colonization, particularly on PS and PET surfaces. Using 16S rRNA metabarcoding, we identified a striking enrichment of Exiguobacterium, followed by Pseudomonas, Acinetobacter and Bacillus genera, containing reported plastic degrading strains, which were strongly correlated with the accelerated breakdown of plastics. However, its role in accelerating plastic breakdown in this study remains unclear and may warrant further investigation. Co-occurrence network analysis revealed a progressive shift in microbial community structure, evolving from highly interconnected networks at day 0 to more specialized, modular clusters by day 40, dominated by Proteobacteria and Firmicutes. Atomic Absorption Spectrometry (AAS) demonstrated significant heavy metal accumulation on plastic surfaces, potentially influencing microbial colonization and activity. While the observed fragmentation of PS foam and PET highlights the susceptibility of certain plastics to environmental stressors, this study also positions microbial colonization as a potential contributor to plastic surface changes, providing novel insights into the interplay between microbial communities and plastic degradation in marine environments.

The hind information: Exploring the impact of physical damage on mask microbial composition in the aquatic environment

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.

Comparison between discarded facemask and common plastic waste on microbial colonization and physiochemical properties during aging in seawater

Facemasks are indispensable for preventing the spread of COVID-19. However, improper disposal of discarded facemasks has led to their contamination in the marine environment. To understand the environmental risk of this emerging plastic pollution, it's important to clarify the features that distinguish discarded facemasks from common plastic waste during aging. This study compared the microbial colonization, degradation-related enzymes, and physicochemical properties among surgical masks, polystyrene cups, polycarbonate bottles, and polyethylene terephthalate bottles in their aging processes in natural seawater. Compared to the other plastic wastes, surgical masks were colonized by the most diverse microorganisms, reaching 1521 unique prokaryotic OTUs after 21-day exposure in seawater. Moreover, the activity of eukaryotic enzymes associated with plastic degradation was 80-fold higher than that in seawater, indicating that the colonized eukaryotes would be the major microorganisms degrading the surgical masks. Meanwhile, the nano-sized defects (depth between 8 and 61 nm) would evolve into cracks of bigger sizes and result in the breakage of the microfibers and releasing microplastics into the ocean. Overall, our study demonstrated a distinctive plastisphere occurred in surgical masks from both microbial and physiochemical aspects. This work provides new insights for assessing the potential risk of plastic pollution caused by the COVID-19 pandemic.