Seasonal hypoxia enhances sediment iron-bound phosphorus release in a subtropical river reservoir.

Dams worldwide commonly accelerate the eutrophication of reservoirs. While the seasonal hypoxia in deep reservoirs is widely acknowledged, there is limited research on its impact on benthic phosphorus (P) cycling and P fraction release from the reservoir sediments. Here we show that seasonal hypoxia enhances sediment P release and P fluxes at the sediment-water interface (SWI) which might alter P dynamics in deep reservoirs. We conducted a detailed measurement of sediment P fractions through the SEDEX approach, combined with a labile P gradient analysis using the diffusive gradients in thin films (DGT) technique to understand P cycling patterns in sediments during the transition period from spring (oxic) to late summer (hypoxic) conditions. The sediment P pool was predominantly composed of iron-bound phosphorus (Fe-P, 76-80 %), primarily due to the widespread occurrence of lateritic red soil (rich in Fe2O3/MnO2) in subtropical areas. More organic-P was observed in summer compared to spring. A significant increase in labile P occurred at the depth of 0-4 cm and 0-1 cm in spring and summer, respectively, where sediment P release was primarily governed by the reduction of Fe-P and the generation of S2-. A higher apparent fluxes of phosphate across the SWI were observed in summer characterized by higher temperature and lower oxygen levels. The current results suggest that seasonal hypoxia was a crucial factor affecting P cycling and diffusion in deep reservoirs. These findings present important implications for the ecology and management of the watershed-coast ecosystem.

Biancaea decapetala (Roth) O.Deg. extract exerts an anti-inflammatory effect by regulating the TNF/Akt/NF-κB pathway.

BACKGROUND: Biancaea decapetala (Roth) O.Deg. (Fabaceae) is used to treat colds, fever, and rheumatic pain caused by inflammation. However, the mechanism underlying its anti-inflammatory properties remains unclear. PURPOSE: This study aimed to evaluate the anti-inflammatory activity of Biancaea decapetala extract (BDE) in vitro and in vivo and explore the possible underlying mechanism and potential targets. METHODS: The release of nitric oxide (NO) and inflammatory cytokines in LPS-stimulated RAW264.7 cells and rats were measured using Griess reagent and enzyme-linked immunosorbent assay (ELISA). Hematoxylin and eosin (H&E) staining was employed to examine the pathology of animal tissues. Transcriptome analysis was performed to screen the pathways related to BDE-mediated inhibition of inflammation, and the expression of related proteins was measured using real-time quantitative polymerase chain reaction (RT-qPCR), western blotting, ELISA, and immunofluorescence methods. Surface Plasmon Resonance (SPR) and the Drug Affinity Reaction Target Stability (DARTS) method were used to verify whether BDE binds to TNF-α target protein, while a L929 cell model and NF-κB gene reporter systematic method were used to investigate the inhibitory effect of BDE on the activity of TNF-α protein. RESULTS: BDE inhibited the expression of TNF-α, IL-1ß, IL-6, and NO in RAW264.7 cells and rats, and improved the pathological changes in lung tissue. RNA-seq showed that BDE may regulate the TNF/Akt/NF-κB pathway to inhibit inflammation onset. BDE significantly downregulated the mRNA expression of TNF-α, IL-6, IL-1ß, and that of relevant proteins, including TNF-α, p-p65, p-Akt, p-IκBα. Furthermore, BDE inhibited the nuclear translocation of NF-κB (p65) and the activation of the Akt pathway by SC79. The L929 cell model, luciferase reporter gene analysis, DARTS, and SPR experiments showed that BDE may bind to TNF-α and inhibit the TNF-α-NF-κB pathway. CONCLUSION: BDE may target TNF-α to inhibit the TNF/Akt/NF-κB pathway, thereby attenuating inflammation. These findings reveal the anti-inflammatory effects and mechanisms of BDE and provide a theoretical basis for the further development and utilization of BDE.

Changes of microbial community structure during the initial stage of biological clogging in horizontal subsurface flow constructed wetlands.

The clogging is a universal problem in constructed wetlands, where microorganisms play an essential role. However, the implication of micro-organism variation due to the clogging is not clear. Four horizontal subsurface flow constructed wetlands (HFCWs) were designed and operated to simulate the process of clogging. The wetland treatment performance and microbial community variation were investigated by regularly monitoring. Results showed the substrate filtration rate and the total phosphorous (TP) removal efficiency consistently decreased and the chemical oxygen demand (COD) and total nitrogen (TN) removal efficiency were at the range of 50%-85% and 10-20%, respectively. The sequencing results indicated that the clogging could affect the richness of bacterial community. The bacterial variation could be attributed to the dissolved oxygen decreasing and organic matter accumulation in the initial clogging period. These findings are expected to provide some theoretical reference for developing the biological methods to indicate the initial clogging in constructed wetlands.