Ecotoxicological Effects Of Fluoroquinolones And Their Removal By Freshwater Microalgae

Antibiotics are increasingly widely used in various fields due to their extremely high inhibitory and killing effects on pathogenic microorganisms.In human medicine,animal husbandry,aquaculture and other industries,the demand for antibiotics is also continuously increasing.As FQs are difficult to be degraded and transformed under natural conditions and can induce the production of antibiotic resistance genes,FQs are attracting more and more public attention as a new pollutant.Microalgae,as the primary producer in the water environment,are a kind of autotrophic plants with rich nutrition and high photosynthetic utilization that are widely distributed on land and sea.Because microalgae can purify the environment,treat refractory organic matters in water and adsorb a certain amount of toxic gases,microalgae are taken as the main research object to explore its toxicological response and removal rate to enrofloxacin.In order to effectively understand the ecotoxicological response and removal effect of microalgae to fluoroquinolones antibiotics,taking microalgae in landscape lakes as the object,laboratory simulation experiments with fluoroquinolones antibiotics are carried out,and the ecotoxicological response and removal efficiency of chlorophyll vulgaris and Chrysosporium ovosporium to fluoroquinolones antibiotics are explored.The specific results are as follows:(1)Enrofloxacin with lower concentration(1mg/L,10mg/L)can increase the total amount of microalgae in water to a certain extent,while enrofloxacin with higher concentration will reduce the total amount of microalgae;Both low concentration and high concentration(1-100mg/L)of enrofloxacin will affect the community composition,dominant species of the community and the content of each component of microalgae,and the effect of high concentration is more significant than that of low concentration.Low concentrations(1mg/L,10mg/L)of enrofloxacin can promote the photosynthetic rate and photosynthetic activity of microalgae,while high concentrations of enrofloxacin show inhibitory effect.Under the stress of enrofloxacin,Scenedesmus quadricauda,Dictyosphaerium sp.and Chlorella vulgaris became dominant species,while the density and photosynthetic activity of other algae decreased significantly.(2)Under different concentrations of enrofloxacin and ciprofloxacin,the biomass,actual light and efficiency and maximum light and efficiency of Chlorella vulgaris decreased with the increase of antibiotic concentration.The growth inhibition rate was between 13% and 40.88%,indicating that enrofloxacin had inhibitory effect on Chlorella vulgaris.The concentrations of superoxide dismutase,catalase and glutathione reductase in Chlorella vulgaris were significantly higher than those in the control group,indicating that common Chlorella vulgaris decomposed peroxide in the body through the enzyme system,thus protecting itself.After 7 days of culture,the MDA content of enrofloxacin stress Chlorella vulgaris was significantly higher than that after 16 days of culture,while the MDA content of norfloxacin stress group was opposite.The results showed that Chlorella vulgaris had lower tolerance to enrofloxacin.On the 7th day of culture,the removal rate of enrofloxacin reached 44.7%,and the removal rate of norfloxacin was significantly lower than that of enrofloxacin.(3)Under different concentrations of enrofloxacin and ciprofloxacin,the biomass and photosynthetic activity of Chrysosporium ovosporium decreased with the increase of antibiotic concentration.At day 7,Chrysosporium ovosporium lost its photosynthetic activity under high concentration(50mg/L)of enrofloxacin.Enrofloxacin had a significant inhibitory effect on Chrysosporium ovosporium(p < 0.01).Under the stress of 1,5mg/L quinolone antibiotics,the concentrations of SOD,CAT and GSH reductase of Chrysosporium ovosporium increased with the increase of antibiotic concentration.When the concentration exceeded 20mg/L,the activity of oxidase was lower than that of the control group due to the inactivation of Chrysosporium ovosporium.After 16 days of culture,the MDA content of Enrofloxacin-stressed Chrysosporium ovosporium increased,indicating that the biofilm damage of Chrysosporium ovosporium increased with the increase of concentration.The removal effect of Chrysosporium ovosporium on enrofloxacin is higher than that of norfloxacin.