The interactions between dissolved organic carbon and marine microbial communities across diverse climatic zones

The microbial carbon pump (MCP) theory highlights the critical role of marine microbes in transforming labile dissolved organic carbon into recalcitrant organic carbon (RDOC), thereby facilitating long-term carbon sequestration in the ocean. However, the ecological mechanisms by which DOC shapes microbial community structure and function across global marine environments remain poorly understood. This study integrated 1090 global marine microbial 16S rRNA amplicon datasets spanning 2013 to 2023, excluding lab-based studies, extreme event samples, and low-quality data. Using QIIME 2 and Vsearch, we analyzed microbial community dynamics driven by DOC. Results reveal that DOC concentrations are positively correlated with microbial phylogenetic dissimilarity, with correlation coefficients (R) ranging from 0.22 to 0.72 and p-values below 0.05, suggesting strong DOC-mediated structuring of community composition. Co-occurrence network analyses show more complex microbial interactions in oligotrophic waters, with Pelagibacterales identified as keystone taxa. In contrast, eutrophic waters are characterized by enhanced metabolic capacity for carbon and nitrogen cycling. Furthermore, high-DOC regions in cold zones show deterministic community assembly, whereas increasing DOC in temperate zones correlates with the prevalence of stochastic processes. This study provides the global-scale elucidation of the coupling mechanism between microbial functions and community assembly under DOC gradients, offering multidimensional empirical support for refining the MCP theoretical framework.