Hydraulic conditions control the abundance of antibiotic resistance genes and their potential host microorganisms in a frequently regulated river-lake system.

Antibiotic resistance genes (ARGs) are a growing problem that is widespread in river-lake ecosystems, where they pose a threat to the aquatic environment's health and public safety. These systems serve as critical nodes in water management, as they facilitate the equitable allocation of water resources through long-term and frequent water diversions. However, hydrological disturbances associated with water-regulation practices can influence the dynamics of their potential host microorganisms and associated resistance genes. Consequently, identifying the key ARGs and their resistance mechanisms in heavily regulated waters is vital for safeguarding human health and that of river-lake ecosystems. In this study, we examined the impact of water-regulation factors on ARGs and their hosts within a river-lake continuum using 16S rRNA and metagenomic sequencing. We found that a significant increase in ARG abundance during regulation periods (p < 0.05), especially in the aquatic environment. Key resistance genes were macB, tetA, evgS, novA, and msbA, with increased efflux pinpointed as their principal resistance mechanism. Network analysis identified Flavobacteriales, Acinetobacter, Pseudomonas, Burkholderiaceae, and Erythrobacter as key potential host microorganisms, which showed increased abundance within the water column during regulation periods (p < 0.05). Flow velocity and water depth both drove the host microorganisms and critical ARGs. Our findings underscore the importance of monitoring and mitigating the antibiotic resistance risk during water transfers in river-lake systems, thereby supporting informed management and conservation strategies.

Indicatory bacteria and chemical composition related to sulfur distribution in the river-lake systems.

Sulfate related water quality and trophic status are crucial to operation of water diversion. Though the sulfur geochemistry in the lake sediment have been well studied, the effective indicator of surrounding environment conditions related to sulfur in river-lake systems are still unknown. In this study, Dongping Lake (DPH), Weishan Lake (WSH), and Hanzhuang trunk canal (HZQ) were selected as the typical river-lake systems in the eastern of China. Different spatial variations in sedimentary sulfate, total sulfur, and elemental composition of sediments were investigated in these areas. The relatively high sulfate in surface water and sediments appeared in portions of WSH. The biodiversity of HZQ and WSH surface sediments was much higher than that of DPH. Pseudomonas, Acinetobacter, and Thiobacillus were the dominant genera of the river-lake systems. Among the different genera in distribution, genera such as Malikia, Sulfurovum and Lysinibacillus were significantly negatively correlated with sulfur related environmental factors. While the genera such as Pseudomonas, Vogesella and Acinetobacter were significantly positively correlated with these factors. Compared with connectivity in the largest interaction network, bacteria such as Proteus, Acidobacter and Chlorobacteria were identified as indicatory taxa to infer sulfate related conditions in the river-lake systems.

Water quality modeling of a prairie river-lake system.

Eutrophication of an under-ice river-lake system in Canada has been modeled using the Water Quality Analysis Simulation Program (WASP7). The model was used to assess the potential effect on water quality of increasing inter-basin transfer of water from an upstream reservoir into the Qu'Appelle River system. Although water is currently transferred, the need for increased transfer is a possibility under future water management scenarios to meet water demands in the region. Output from the model indicated that flow augmentation could decrease total ammonia and orthophosphate concentrations especially at Buffalo Pound Lake throughout the year. This is because the water being transferred has lower concentrations of these nutrients than the Qu'Appelle River system, although there is complex interplay between the more dilute chemistry, and the potential to increase loads by increasing flows. A global sensitivity analysis indicated that the model output for the lake component was more sensitive to input parameters than was the model output of the river component. Sensitive parameters included dissolved organic nitrogen mineralization rate, phytoplankton nitrogen to carbon ratio, phosphorus-to-carbon ratio, maximum phytoplankton growth rate, and phytoplankton death rate. Parameter sensitivities on output variables for the lake component were similar for both summer (open water) and winter (ice-covered), whereas those for the river component were different. The complex interplay of water quality, ice behaviors, and hydrodynamics of the chained river-lake system was all coupled in WASP7. Mean absolute error varied from 0.03-0.08 NH4-N/L for ammonium to 0.5 to1.7 mg/L for oxygen, and 0.04-0.13 NO3-N/L for nitrate.