Study On The Treatment Of Microcystis Aeruginosa With Typical Algaecides Under The Reguliation Of Antibiotics

Low concentrations of antibiotics could stimulate the growth of Microcystis aeruginosa and the release of microcystins?MCs?.Whether the stimulation effects will interfere with the control of cyanobacterial bloom has not been reported.In this study,five widely detected antibiotics?amoxicillin,spiramycin,tetracycline,ciprofloxacin and sulfamethoxazole?with high antibacterial activities were selected as target chemicals.H₂O₂,glyphosate,CuSO₄ and KMnO₄ were selected as typical algaecides.The regulatory effects and mechanisms of mixed antibiotics on the treatment of cyanobacteria at an environmentally relevant concentration?100 ng/L?were studied through a 7-day exposure test.Coexisting antibiotics significantly stimulated?p<0.05?the cell density and the growth rate in Microcystis aeruginosa exposed to 15-45 ?M H₂O₂,40-60 mg/L glyphosate,0.05-0.15 mg/L CuSO₄ and 0.16-1 mg/L KMnO₄.Coexisting antibiotics reduced the effect of algaecides and pose a threat to the aquatic ecosystem by stimulating the synthesis and release of MCs during algaecides treatment.According to the increased contents of chlorophyll a and protein,decreased content of malondialdehyde,and decreased activities of superoxide dismutase and glutathione S-transferase,antibiotics may reduce the toxicity of algaecides through the stimulation of photosynthesis and functional proteins and the reduction of oxidative stress.The reduction of algaecide toxicity by mixed antibiotics was not significant at high exposure dose of algaecides?p>0.05?.In order to eliminate the interference effect of coexisting antibiotics,high algaecide doses that are>45 ?M for H₂O₂,>60 mg/L for glyphosate,>0.15 mg/L for CuSO₄ and>1 mg/L for KMnO₄ are recommended.This study provides insights into the ecological hazards of antibiotic contaminants and the best management strategies for cyanobacterial removal under combined antibiotic pollution conditions.