Bacterial community assembly in surface sediments of a eutrophic shallow lake in northern China

Anthropogenic perturbations make negative effects on wetland ecosystems, such as increasing levels of eutrophication. Under variable environmental conditions, studying the processes and mechanisms underlying their spatial distribution is critical to biogeochemical significance of microorganisms. In order to understand the changes in sediment bacterial community and their assembly with long-term eutrophication of the Baiyangdian Lake of China, we explored the microbial communities for 24 surface sediment samples using high throughput sequencing of V3-V4 region of 16S rRNA gene, meanwhile we employed Neutral community model (NCM) to characterize the community assembly processes. Then, the β-nearest taxon index (βNTI) based on a null model was used to provide a quantitative description of the assembly processes of the bacterial community. Dispersal limitation, quantified by βNTI, accounted for ∼64.6% of all assembly processes. As the increasing levels of eutrophication, deterministic processes of bacterial community assembly may be enhanced. Moreover, the significant correlation between the βNTI and change in water NO₃⁻ or sediment pH might lead to deterministic processes. There was some selection pressure acting within the Baiyangdian lake sediments. The neutral community model properly explained bacterial community assembly. The NO₃⁻, NH₄⁺, pH and EC were main influencing factors on the composition of the bacterial community. The overlying water NO₃^−, surface water NO₃⁻ and sediment pH were the three most crucial environmental factors to drive bacterial assembly. The findings revealed that Group 4 with relatively stronger deterministic processes as a more eutrophic area should be monitored as an indicator for eutrophication governance.