Assessment of soil microbial communities and diversity in typical coastal wetlands along a succession gradient: Implications for reconstructing the long-term evolution of coastal wetlands

To more precisely reconstruct the long-term evolutionary processes of coastal wetlands in the past using microbial deposition records, it is essential to differentiate various types of coastal wetlands along sea-land gradients based on their community and diversity characteristics, and to identify the primary factors influencing them. In this study, based on high-throughput sequencing technology, we revealed the microbial community composition and diversity characteristics of four major coastal wetlands in Bohai Bay, including Lagoon & Estuary (L&E), Suaeda (SU), Freshwater-Phragmites (F-P), and Freshwater-Weeds (F-W), and discussed their relationship with environmental factors. The results showed that dominant microbial communities had clear indicative significance for corresponding wetlands. In the L&E wetlands, the microbial communities are characterized by dominant taxa spanning multiple taxonomic ranks: Desulfobacterota, Gammaproteobacteria, and Desulfuromonadia. In SU wetlands, the indicator taxa comprised Flavobacteriales, Balneolales, and Planococcaceae. In F-P wetlands, the differentially abundant taxa included Acidobacteriota, Myxococcota, Gemmatimonadota, and Planctomycetota. Salinity and vegetation cover were the most important factors affecting soil microbial composition in Bohai Bay coastal wetlands. F-P wetlands had the highest richness and evenness of microbial species, followed by L&E, F-W, and SU wetlands. Na⁺ and Cr contents were negatively correlated with microbial diversity, while vegetation cover, TOC and P contents were positively correlated with microbial diversity. Our study emphasized the significance of understanding the relationship between microbial community composition and environmental factors in different wetlands in Bohai Bay, and lay a foundation for wetland biodiversity conservation and reconstruction of past ecosystem succession processes.