Role of biogeochemical and hydrodynamic characteristics in simulating nitrogen dynamics in river confluence.

The confluence area is the link of different river systems, whose specific hydrodynamic characteristics can significantly influence mass transport and distribution, which can further make a difference to microorganism growth and biogeochemical processes. However, the specific influences of hydrodynamic characteristics in confluence on formation processes of microbial communities and the biogeochemical processes remain unclear. To this end, the present study established an indoor self-circulation confluence flume and conducted 28-day culture experiment to thoroughly investigate the characteristics of microbial communities and nitrogen dynamics in sediment of confluence area.

Deciphering solute transport, microbiota assembly patterns and metabolic functions in the hyporheic zone of an effluent-dominated river.

We lack a clear understanding of how anthropogenic pressures, exemplified by effluent discharge from wastewater treatment plants, destabilize microbial communities in the hyporheic zone (HZ) of receiving rivers. In this study, the spatiotemporal characteristics of hydrological parameters, and the physicochemical properties of surface and subsurface water in a representative effluent-dominated river were monitored. Sequencing of 16S rRNA amplicons and metagenomes revealed the microbial community structure in the HZ of both effluent discharge area and downstream region.

River connectivity determines microbial assembly processes and leads to alternative stable states in river networks.

River network is a common form of lotic ecosystems. Variances in river connection modes would form networks with significantly different structures, and further affect aquatic organisms. Microbial communities are vital organisms of river networks, they participate in numerous biogeochemical processes.

Determination of the direct and indirect effects of bend on the urban river ecological heterogeneity.

The ecological heterogeneity created by river bends benefits the diversity of microorganisms, which is vital for the pollutant degradation and overall river health. However, quantitative tools capable of determining the interactions among different trophic levels and species are lacking, and research regarding ecological heterogeneity has been limited to a few species. By integrating the multi-species-based index of biotic integrity (Mt-IBI) and the structure equation model (SEM), an interactions-based prediction modeling framework was established.

Integrating experiments with system-level biogeochemical modeling to understand nitrogen cycling of reservoir sediments at elevated hydrostatic pressure.

Impoundment of rivers to construct reservoirs for hydropower and irrigation greatly increase the hydrostatic pressure acting on river sediments with potential repercussions for ecosystem-level microbial activity and metabolism. Understanding the functioning and responses of key biogeochemical cycles such as that of nitrogen cycling to shifting hydrostatic pressure is needed to estimate and predict the systemic nutrient dynamics in deep-water reservoirs. We studied the functioning of bacterial communities involved in nitrogen transformation in bioreactors maintained under contrasting hydrostatic pressures (0.

Coupling Genomics and Hydraulic Information to Predict the Nitrogen Dynamics in a Channel Confluence.

The simulation of nitrogen dynamics in urban channel confluences is essential for the evaluation and improvement of water quality. The omics-based modeling approaches that have been rapidly developed have been increasingly applied to characterize metabolisms of the microbial community and transformation of the associated materials. However, the transport of microorganisms and chemicals within and among different phases, which could be the rate-limiting step for the nitrogen dynamics, are always neglected or oversimplified in omics-based models.

Dams shift microbial community assembly and imprint nitrogen transformation along the Yangtze River.

Dams are important for flood control, water storage, irrigation, electric generation, navigation, and have been regarded as the largest anthropogenic disturbance in aquatic ecosystems. However, how dams impact nitrogen transformation on a large watershed scale remained less studied. To explicitly address the impact of dams on nitrogen transformation, we used 16S rRNA gene sequencing to investigate the microbial dynamics and ecological processes under different dam conditions along the Yangtze River, as microbial communities are playing a key role in aquatic nitrogen transformation.

Integrating Microbial Community Assembly and Fluid Kinetics to Decouple Nitrogen Dynamics in an Urban Channel Confluence.

Understanding the characteristics of biogeochemical processes in urban channel confluences is essential for the evaluation and improvement of water environmental capacity. However, influences of biogeochemical processes in confluence were always overlooked or simply parametrized since the transformation processes controlled by microbial community assembly were hard to quantify. To address this knowledge gap, the present study proposed a novel mathematical modeling system, based on microbial community assembly theory and fluid kinetics, to decouple nitrogen dynamics into flow-induced transport and microorganism-induced transformation processes, and quantified their contributions to nitrogen concentrations.

Bend-induced sediment redistribution regulates deterministic processes and stimulates microbial nitrogen removal in coarse sediment regions of river.

Understanding the differences of biogeochemical processes between straight and bent channel is important for weighting them in urban river planning and reconstruction. Shifts in the assembly of the sediment microbial community of bent channels are key, but understudied, component of bend-induced increases in biogeochemical reaction rates. Here, the assembly of microbial community and its feedback to nitrogen transformation in urban river bends were firstly studied by coupling ecological theory, aqueous biogeochemistry, DNA sequencing, and hydrodynamic profiling.

Identifying key environmental factors for enhancing the pollutant removal potential at a river confluence.

The confluence area of river networks is a hot spot for pollutant removal. As an essential part of the river ecosystem, sediment bacterial communities played a crucial role in the removal of pollutants. However, how the potential of sediment bacterial communities can be enhanced toward the removal of pollutants remains unclear.