Microbial diversity and water quality changes in mangrove sediments in Quanzhou Bay.

This study investigated the diversity, composition, and environmental drivers of bacterial communities in the mangrove sediments of Quanzhou Bay, a subtropical estuary under anthropogenic pressure. Using high-throughput sequencing of the 16S rRNA gene, we analyzed samples from four sites (Fengze-FZ, Jinjiang-JJ, Luojiang-LJ, and Shishi-SS) representing a gradient of terrestrial influence and environmental conditions. The bacterial communities were predominantly composed of Pseudomonadota and Chloroflexi, a pattern consistent with global mangrove ecosystems but with distinct local structuring. Beta-diversity analyses (NMDS/PCA) revealed a significant spatial divergence, with the FZ site forming a distinct cluster separate from JJ, LJ, and SS, correlating with its unique environmental profile. Redundancy analysis (RDA) identified dissolved oxygen (LDO) and salinity as the key environmental factors shaping community structure. Functional prediction indicated a conserved potential for core metabolic processes (e.g., amino acid biosynthesis, bacterial chemotaxis) across sites, suggesting functional redundancy, while differences in the relative abundance of these pathways pointed to adaptive metabolic adjustments along the environmental gradient. Our findings demonstrate that the sedimentary microbial community structure in Quanzhou Bay is primarily shaped by localized environmental heterogeneity, providing critical insights into the microbial ecology of mangroves in urbanized coasts and a baseline for assessing ecosystem health and biogeochemical functioning under anthropogenic influence.