Understanding the effects of eutrophication on heterotrophic bacteria, a primary responder to eutrophication, is critical for predicting the responses of ecosystems to marine environmental pollution. Vibrio are indigenous in coastal water and of significance to geochemical cycling and public health. In this study, we investigated the diversity and assembly features of Vibrio, as well as their relationship with the environmental factors in the subtropical Beibu Gulf. We found that the alpha diversity of Vibrio increased in parallel with the trophic state they occupy. A Mantel test indicated that the trophic state was correlated to Vibrio beta diversity and the correlation gradually strengthened at higher trophic states. Variation partitioning analysis suggested that the geographic distance was an important factor impacting the variables of Vibrio communities in all the samples, but nutrients exerted more influence in the more highly eutrophic samples. Our results demonstrated that stochastic processes govern the turnover of marine Vibrio communities in the Beibu Gulf and that ecological drift was the most important process for assembly of the Vibrio communities.

Leaf endospheres harbor diverse bacterial communities, comprising generalists and specialists, that profoundly affect ecosystem functions. However, the ecological dynamics of generalist and specialist leaf-endophytic bacteria and their responses to climate change remain poorly understood. We investigated the diversity and environmental responses of generalist and specialist bacteria within the leaf endosphere of mangroves across China. Our findings show a predominance of specialists in the mangrove leaf endosphere. Temperature is the key factor driving community dissimilarity in both groups, yet it negatively influences the alpha diversity. Soil nutritional factors, particularly phosphate for generalists and total organic carbon for specialists are critical in shaping the functional profiles. Interestingly, temperature has a limited impact on functional profiles. Stochastic processes govern community assembly in both bacterial groups, altering the β-nearest taxon indices as temperatures increase. Our findings indicate that the halophytic leaf endosphere favors microbial niche specialization, due to its unique microenvironment and discrete niches, showing thermal sensitivity in terms of the microbial community profile. This study provides insights into niche differentiation and environmental adaptation mechanisms of leaf endophytic microbes in woody halophytes in response to environmental perturbations.

Mangrove ecosystems are valuable coastal ecosystems; however, studies on the diversity and functional features of their soil fungal communities during restoration are limited. In this study, we examined fungal diversity and trophic modes across mudflat, young mangrove, and mature mangrove stages. We found that Ascomycota and Basidiomycota were the dominant phyla, with saprotrophs as the most abundant trophic mode. The abundance of the major phyla and trophic modes significantly varied across restoration stages. Although fungal alpha (α)-diversity remained stable among the stages, beta (β)-diversity showed significant differentiation. Spearman’s analysis and partial Mantel tests revealed that total nitrogen and inorganic phosphorus significantly influenced the fungal α-diversity, whereas temperature and pH primarily shaped the fungal β-diversity. Total nitrogen and carbon were key factors affecting the trophic mode α-diversity, whereas total phosphorus and inorganic phosphorus were the main drivers of the trophic mode β-diversity. Variation partitioning analysis confirmed that nutrients, rather than soil properties, were the primary factors shaping fungal communities and trophic modes. Random forest analysis identified key bioindicators, including species such as Paraphyton cookei, and trophic modes such as saprotrophs, both of which were strongly influenced by soil carbon. These findings advance our understanding of fungal ecology in mangrove restoration.

Soil fungi in mangroves are diverse and crucial for organic matter decomposition and element cycling. However, the drivers influencing network complexity and the stability of fungal communities across different mangrove soil habitats remain unclear. This study investigated the main factors driving the composition, diversity, complexity, and stability of fungal communities in clay loam and sandy soils in mangrove ecosystems. Results showed that Dothideomycetes and Sordariomycetes dominated in clay loam and sandy soils, respectively. Sandy soils exhibited higher alpha diversity than clay loam. Beta diversity analysis revealed significant differences in the fungal community structure between the two soil types. Network analysis demonstrated higher complexity and stability of fungal communities in clay loam than in sandy soil. Spearman’s correlation analysis revealed that NH₄⁺-N and total nitrogen were the main factors affecting complexity and stability in clay loam, respectively. Partial least squares path modeling demonstrated that alpha diversity and soil properties were closely linked to the complexity and stability of fungal communities in clay loam, whereas beta diversity was the primary driver in sandy soil. Our study enhances the understanding of the mechanisms that maintain fungal diversity and community stability in mangrove ecosystems, with important implications for restoring vegetation in degraded areas.

Microbial immigration is an ecological process in natural environments; however, the ecological trade-off mechanisms that govern the balance between species extinction and migration are still lacking. In this study, we investigated the mechanisms underlying the migration of diazotrophic communities from soil to leaves across six natural mangrove habitats in southern China. The results showed that the diazotrophic alpha and beta diversity exhibited significant regional and locational variations. The diazotrophic species pool gradually increased from the leaves to nonrhizosphere soil at each site, exhibiting a vertical distribution pattern. Mantel test analyses suggested that climate factors, particularly mean annual temperature, significantly influenced the structure of the diazotrophic community. The diazotrophic community assembly was mainly governed by dispersal limitation in soil and root samples, whereas dispersal limitation and ecological drift were dominant in leaves. Partial least squares path modeling revealed that the species pool and soil properties, particularly the oxidation-reduction potential and pH, were closely linked to the species-immigration ratio of diazotrophic communities. Our study provides novel insights for understanding the ecological trait diversity patterns and spread pathways of functional microbial communities between below- and aboveground habitats in natural ecosystems. IMPORTANCE: Environmental selection plays key roles in microbial transmission. In this study, we have provided a comprehensive framework to elucidate the driving patterns of the ecological trade-offs in diazotrophic communities across large-scale mangrove habitats. Our research revealed that Bradyrhizobium japonicum , Marinobacterium lutimaris , and Agrobacterium tumefaciens were more abundant in root-associated soil than in leaves by internal and external pathways. The nonrhizospheric and rhizospheric soil samples harbored the most core amplicon sequence variants, indicating that these dominant diazotrophs could adapt to broader ecological niches. Correlation analysis indicated that the diversities of the diazotrophic community were regulated by biotic and abiotic factors. Furthermore, this study found a lower species immigration ratio in the soil than in the leaves. Both species pool and soil properties regulate the species-immigration mechanisms of the diazotrophic community. These results suggest that substantial species immigration is a widespread ecological process, leading to alterations in local community diversity across diverse host environments.