Soil Microbiome of Tropical Seasonal and Permanent Small Wetlands

Characterisation of the microbial communities of two small tropical wetlands under two distinct hydrological regimes (permanent and seasonal), across a rainy and dry season was performed by 16S rRNA amplicon sequencing. We identified 48 bacterial phyla across the two wetland types, seasons and depths and 83% of the bacterial sequences consistently corresponded to six phyla: Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Proteobacteria and Verrucomicrobia. The seasonal wetland presented a predominance of Chloroflexi, Nitrospirae, Actinobacteria and Acidobacteria, whereas the permanent wetland showed higher relative abundances of Planctomycetes, Bacteroidetes, Proteobacteria and Firmicutes. Archaeal communities also differed, with Crenarchaeota predominating in the seasonal and Euryarchaeota in the permanent wetland. Microbial communities showed pronounced compositional shifts across wetland type, season and depth, while maintaining stable alpha diversity, with depth was the dominant driver. Functional inference suggested that aerobic ammonia oxidation, nitrate reduction and sulphur compound respiration were the predominant putative metabolic pathways in the seasonal wetland and methanogenesis, fermentation, dark hydrogen oxidation, nitrogen fixation, photoautotrophy, ureolysis and hydrocarbon degradation in the permanent wetland. The permanent wetland exhibited sparse correlation with environmental drivers, consistent with long-term saturation and chronic nutrient limitation, while the seasonal wetland presented influence of pH, nutrients and SOC on microbial community structure.