Contrasting the diversity patterns and processes of microbial community assembly in water and sediment in Lake Wuchang, China

Abstract Background : Microorganisms are an integral component of lake ecosystems, as they play crucial roles in material circulation and energy flow. Understanding the distribution of bacterial communities, their mechanisms of formation, and the ecological functions of such communities in lakes is essential for the diagnosis and management of lake ecosystems. Results : We explored the diversity patterns and processes of microbial community assembly in the water and sediment of Lake Wuchang (China) using high-throughput sequencing of 16S rRNA gene amplicons on the Illumina platform. The results revealed a higher microbial α-diversity in the sediment than in water ( P < 0.01), and the most common bacterial phyla in the water column were Proteobacteria (average 39.19%), Cyanobacteria (24.12%), and Actinobacteria (15.73%), while the dominant bacterial phylum in the sediment was Proteobacteria (38.90%), followed by Acidobacteria (9.84%), Chloroflexi (8.93%), and Nitrospirae (8.61%). Through functional annotation, functions related to phototrophy and nitrogen metabolism primarily occurred in the water column and sediment, respectively. Unconstrained principal coordinates analysis (PCoA) showed that in water samples, the microbial communities from different seasons were divided into three groups, while samples collected from sediment revealed no such dispersion. These results were supported by the analysis of similarities, as the difference between season groups in water was greater than between groups in sediment (R = 0.759, p = 0.001 and R = −0.012, p = 0.488, respectively). According to Pearson correlation analysis, different environmental variables showed significant roles in shaping the microbial communities, as water temperature, dissolved oxygen, water depth, total nitrogen, ammonium, and nitrite were key factors for microbial community structure in the water column, while TN in sediment, conductivity, and organic matter were key factors in sediment. However, we found that stochastic processes (the value of |βNTI| < 2) dominated community assembly in both the water column and sediment of Lake Wuchang. Conclusions: This study represents one attempt to explore the microbial diversity patterns and the community assembly mechanisms in lake ecosystems and the influences of sampling scale. The results will provide a foundation for microbial development and utilization in lake water column and sediment under the circumstances of increasing tendency of lake ecological fishery.