Effects of substrate materials on microbial diversity and network dynamics: Comparing microplastics and silica-based...

Attached microbes play a crucial role in the degradation of pollutants and microplastics within lake ecosystems. However, it remains poorly understood how different substrate materials affect the diversity and co-occurrence patterns of attached microbes. Here, a 70-day mesocosm experiment was conducted using three types of silicon-based materials and two types of microplastics as substrates. The successional dynamics of attached bacterial communities were characterized using 16S rRNA gene sequencing. Our results revealed significant differences in the bacterial community composition and structure between the silica-based material (SG) and microplastic (MP) groups (Adonis, P < 0.001). Among them, bacterial diversity in the MP group was significantly lower than that in the SG group and exhibited a declining trend during the late stage of attachment. Random forest analysis indicated that the dominant bacterial communities in the MP group were relatively simpler than those in the SG group. In the MP group, Stenotrophomonas and Methyloversatilis dominated the early stage of attachment, followed by Brevundimonas in the middle stage. In the late stage, genera such as CL500-29_marine_group, Parviterribacter, and Phreatobacter co-dominated the community structure. Furthermore, substrate materials significantly influenced the co-occurrence network patterns of attached bacterial communities. Specifically, the SG group exhibited an initial decrease followed by an increase in network complexity over time, whereas the MP group showed the opposite trend. Network stability was significantly higher in the SG group than in the MP group, with both groups demonstrating a temporal pattern of initial increase followed by a decrease. Overall, these findings provide new insights into the responses of attached microbes to different substrate materials, the evolution of network complexity and stability. Our study could inform ecological management strategies for mitigating microplastic pollution and regulating attached microbial communities.