Insights into Bacterial Communities and Diversity of Mangrove Forest Soils along the Upper Gulf of Thailand in Response to Environmental Factors

SIMPLE SUMMARY: Mangrove forests are unique ecosystems located in tropical and subtropical tidal areas worldwide. In mangrove ecosystems, the bacterial community mediates nutrient transformation and therefore is essential for mangrove productivity and maintenance. The bacterial community structure in mangrove soil that is influenced by environmental factors thus merits comprehensive study. Illumina next-generation sequencing detected the unique biomarkers and predominant genera that established distinct niches in the mangrove soils along the Upper Gulf of Thailand. The bacterial diversity and community structure of the Mae Klong Estuary site were most dissimilar to those of the other sites, while the bacterial communities of Chaopraya Estuary, Laemphakbia Promontory, and Pranburi forest park sites were closer to each other. The Kungkrabaen Bay and Black Sand Beach sites had bacterial communities which were closest to each other. The mangrove soils were found variable with respect to pH and had low amounts of organic matter (OM). Soil OM was the major factor that modulated the bacterial community structure. The groups of ammonia-oxidizing, sulfate-reducing, and methanogenic bacteria were the significant biomarkers distributed in these mangrove soils. ABSTRACT: The comprehensive data for the dynamic adaptation of bacterial community structure in response to environmental factors is important for the maintenance of the mangrove ecosystem. This aspect was investigated with soils and surface water from six mangrove forests in six provinces along the Upper Gulf of Thailand shoreline. Mangrove soils were variable with respect to pH (acidic to slightly alkaline) and had low amounts of organic matter (OM). Illumina next-generation sequencing attested that the number of observed species as well as the bacterial diversity and richness among all sites were not significantly different. The gamma-, alpha-Proteobacteria, Desulfobacteria, Bacteroidia, Anaerolineae, Bathyarchaeia, Acidobacteriae, Nitrososphaeria, Clostridia, and Thermoplasmata were more abundant bacterial classes present in all sites. Soil OM was the major factor that mostly modulated the bacterial community structure, while salinity influenced the number of observed species and bacterial richness. These results provide informative data on the bacterial community, in response to both environmental factors and heavy metal pollutants, that is prominent for sustainable development and management of mangrove forests.