Revealing the bacterial diversity and variation of white filamentous microbial mats in marine mangroves of Guadeloupe Island in relation to human activities

Abstract White filamentous microbial mats are complex benthic communities, typically structured by sulfur-oxidizing bacteria from the Beggiatoaceae family, yet their diversity and ecological responses in mangrove ecosystems remain poorly characterized. Here, we provide a high-resolution analysis of bacterial communities associated with white microbial mats in marine mangrove sediments of Guadeloupe using 16S rRNA metabarcoding. Bacterial community composition was compared across sites with different levels of anthropogenic impact (protected, natural, and urban). While overall diversity remained stable, richness differed significantly between conditions, and beta diversity analyses revealed clear compositional structuring along the disturbance gradient. A conserved core microbiome was identified across all sites, whereas rare taxa were detected exclusively in urban sites, including Ferrimicrobium, Thermonospora, Alcanivorax, and Serratia, which has been previously associated with human-induced environmental changes. In contrast, Prosthecochloris and Chlorobaculum were highly abundant in protected sites, whereas Sulfurovum and Sulfurimonas dominated urban environments. The relative abundance of Beggiatoaceae also varied across sites, suggesting sensitivity to anthropogenic disturbance. Despite these compositional shifts, measured physicochemical parameters did not significantly correlate with the community structure, suggesting that microbial mat organization is influenced by fine-scale or unmeasured environmental gradients. Together, these findings indicate that white microbial mats respond to anthropogenic disturbance primarily through taxonomic restructuring rather than loss of diversity, highlighting their potential as sensitive indicators of environmental change in mangrove ecosystems.