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.

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.