Microplastic type and concentration affect prokaryotic community structure and species coexistence in deep-sea cold seep sediments

As important methane hydrate storage sites, cold seep areas are threatened by microplastics (MPs) contamination. To assess the environmental impact of MPs on microbial communities in cold seep sediments, an incubation experiment was conducted using cold seep sediment amended with different concentration of polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP) microplastics. The results showed that the different type and concentration of MPs significantly altered the prokaryotic community structures. The PE and PET addition highly changed the relative abundance of bacterial taxa in the bacterial community, while the proportion of archaeal species in the archaeal community was significantly altered in 0.5 % MPs treatments. All of the MPs reduced the network complexity of the bacterial and archaeal communities, such as the lower average degree and greater average path length. Furthermore, the MPs treatments also significantly decreased the network stability of prokaryotic communities. The lower network complexity led to lower network stability was observed in the archaeal community. The formation of oxidative functional groups on PE and PET MP surface based on FTIR analysis suggested that biodegradation could occur in cold seep sediment. Together, these results provide new evidence that MPs could change the structures and species coexistence of prokaryotic communities in cold seep sediments.