The occurrence of cyanobacterial species, especially toxic ones, poses a great threat to coastal and estuary areas. In this study, the toxigenic Microcystis aeruginosa (M. aeruginosa) FACHB-905 was exposed to BG-11 medium with different salinities (1, 4, 7, 10 and 15 ppt) to investigate the physiological responses of this species in terms of oxidative stress, chl a fluorescence and microcystins (MCs) contamination. The results showed that low salinity (≤7 ppt) favored the electron transfer of photosystem II, which promoted the growth and photosynthesis of M. aeruginosa and induced MCs production. However, increased salinity (≥10 ppt) suppressed the growth and photosynthesis of M. aeruginosa and aggravated the oxidative stress of the strain. Salinity of 15 ppt reduced MCs contamination and caused irreversible damage to the photosynthetic system of M. aeruginosa, leading to the lysis and death of algal cells. These results indicated that changes in salinity exerted important regulations on the growth and MCs contamination of the toxic M. aeruginosa, which may provide a reference for the risk assessment of the harmful cyanobacterial species in the coastal and estuary areas.

Understanding the drivers of macroinvertebrate community structure is fundamental for adequately controlling pollutants and managing ecosystems under global change. In this study, the abundance and diversity of benthic macroinvertebrates, as well as their chemical parameters, were investigated quarterly from August 2014 to April 2015 in four reaches of the Huai River basin (HRB). The self-organizing map (SOM) algorithm and canonical correspondence analysis (CCA) were simultaneously applied to identify the main factors structuring the benthic community. The results showed that the benthic community structure was always dominated by gastropoda and insecta over seasons and presented obvious spatial and temporal heterogeneity along different pollution levels. The insects were always the top contributors to number density of the benthic community, except for the summer, and the biomass was mainly characterized by mollusca in all seasons. Statistical analysis indicated that TN and NH₃-N in water, as well as Hg, As, Cd, and Zn in sediments, were the dominant factors structuring the community, which determined the importance of sediment heavy metal concentrations in explaining the benthic community composition in comparison with other factors. These major factors should be given priority in the process of river pollutant control, which might be rated as a promising way to scientifically improve river health management and ecological restoration.

The biotoxicity of heavy metals in water has always been the focus of ecological health research. In this study, the oxidative stress-associated toxicity of cadmium (Cd) and lead (Pb) at environmentally relevant concentrations on the hepatopancreas of Macrobrachium nipponensis was investigated based on multiple biomarker responses in a 28-day indoor exposure study. Changes in integrated biomarker responses (IBR) and their interactivity were subsequently analyzed. No dead individuals were found across any of the tested conditions. The chronic toxicity of heavy metals depended on their type and exposure time at the same concentration. At low concentrations, organisms have a regulatory capacity to cope with the excess reactive oxygen species (ROS) induced by Pb stress over time. In detail, the activity of superoxide dismutase (SOD) was inhibited by Pb stress at a high concentration as time passed. The sensitivity of metallothionein (MT) to Cd was stronger than Pb, and the potential for Cd to cause lipid peroxidation damage was higher than Pb. At the same time, Pb had a greater disturbance effect on the nervous system than Cd, especially in the early exposure stage. The contribution of Cd and Pb to the interaction effect varied dynamically with time and concentration of exposure, but mostly showed antagonism. The results of this study have important significance for guiding the diagnosis of ecological water health, the amendment of water quality criteria, and the management of wastewater discharge.

Sewage pre-concentration has been promising for carbon-neutral anaerobic wastewater treatment. Magnetic bio-flocculation, which combines the advantages of adsorption/bio-oxidation processes and magnetic separation for cost-effective, fast, and eco-friendly chemical-additive-free pre-concentration, is proposed in this study. The results show that 85.5–89.5% chemical oxygen demand (COD) removal within 30 min can be achieved. The maximum recovery rate of organic matter (OM) can be increased from 79.6% to 88.2% by replacing aeration with stirring coupled with a magnetic field (MF). This can be attributed to the increased production of loosely bound extracellular polymeric substances (LB-EPS) by 23.7–62.9 mg L⁻¹ and decreased production of the tightly bound EPS (TB-EPS) by 3.8–5.7 mg per g VSS in the stirring set, where the magnetic force alleviated the microbial surface negative charge, strengthened the attachment of magnetic seeds (MS) to sludge through MF-induced extra fragmented LB-EPS and compensated for the negative impact of LB-EPS by intensifying microbial OM capture. The decreased median diameter by 0.93–4.13 μm and the improved fractal dimension ranging from 2.15 to 2.18 further support the above effects. The combination of MS and the MF improved the sludge settleability, which is supported by the maximized hindered settling velocity accelerated by 1.6–7.2 m h⁻¹. The V₀/n values calculated from the Vesilind function, which mean the mass of sludge passing through a unit section per unit time, reached a maximum value of 52.71 after coupling the MS and MF. As such, magnetic bio-flocculation with stirring is found to be promising for achieving optimized practical sewage pre-concentration.