Seasonal community structure and environmental associations of putative pathogenic microorganisms in the Shelf-Margin Sea of the Northwestern South China Sea

Marine pathogenic microorganisms are crucial to ecological health and fishery aquaculture. However, the composition and influencing drivers for pathogenic microorganisms in the Shelf-Margin Sea of the Northwestern South China Sea (SMS-NWSCS) are still unclear. This study applied 16S rRNA and ITS gene high-throughput sequencing combined with multiple bacterial pathogen detection (MBPD) and FUNGuild database to explore putative pathogenic microorganisms in the SMS-NWSCS and to investigate the main environmental associations of the composition, diversity, complexity and stability of putative pathogenic microbial communities. Results showed that Escherichia coli (31.77%), Pseudomonas fluorescens (16.25%) and Sphingomonas paucimobilis (6.90%) were dominant putative pathogenic bacteria, while Pseudozyma sp. (48.36%) and Malassezia globosa (48.34%) dominated the putative pathogenic fungal communities. The putative pathogenic bacterial community exhibited higher alpha diversity in winter, while the fungal community showed greater alpha diversity in summer. Beta diversity analysis revealed significant seasonal dynamics in both putative pathogenic bacterial and fungal communities (bacteria: R 2 = 0.12, p = 0.001; fungi: R 2 = 0.08, p = 0.007). Spearman’s correlation analysis suggested that a suite of environmental factors, including temperature, pH, DO, Chla and nutrients, played significant roles in influencing putative pathogenic microbial community structure. PLS-PM analysis demonstrated that bacterial alpha diversity was positively associated with community complexity (R 2 = 0.10, p < 0.01) and stability (R 2 = 0.45, p < 0.001), and both alpha and beta diversity (R 2 = 0.10, p < 0.05; R 2 = 0.21, p < 0.001) showed positive correlations with the stability of the putative pathogenic fungal community. Our study reveals the seasonal patterns of putative pathogenic microorganisms in the SMS-NWSCS and enhances the understanding of their community maintenance mechanisms.