Study On The Effect Of Sulfonamide Antibiotics On The Growth Of Typical Algae In Reservoir

In recent years,due to the improper use,disposal and management of antibiotics,a large number of antibiotics have entered the water environment.Antibiotics affect the growth of algae and aquatic organisms in the water body,thus affecting the whole aquatic ecosystem.The ecological safety and health safety issues caused by antibiotics are of great concern.Algae is the primary producer of water ecosystem,which plays a very important role in the food chain and ecosystem.In order to explore the effect of antibiotics on algae and its mechanism of action,and accurately assess its ecological risk,two sulfonamides with high detection rate in the water environment of northern China were selected: sulfamethoxazole(SMZ)and sulfadiazine(SMD),taking Chlorella vulgaris(green algae),Microcystis aeruginosa(blue algae)and algae community in a typical reservoir as experimental objects,through analyzing the changes of physiological and biochemical characteristics of two kinds of microalgae and the changes of phytoplankton community structure in a reservoir water,to explore the response mechanism of freshwater microalgae to sulfonamides antibiotic stress.The main conclusions are as follows:(1)Different antibiotics have different effects on the physiology and biochemistry of different algae.Under the influence of SMZ,the growth of Chlorella vulgaris was inhibited in the first three days,and on the seventh day,the growth was promoted by low concentration(<50 mg/L)and inhibited by high concentration(> 80 mg/L),while that of Microcystis aeruginosa was inhibited by SMZ,and the growth inhibition rate was above 90%until the end of the experiment.The inhibition of SMD on the growth of Chlorella vulgaris was "low promoting and high inhibiting",reached the maximum on the 7th day,and then decreased gradually;the inhibition of Microcystis aeruginosa had a concentration effect relationship,and the inhibition increased with the increase of SMD exposure time.(2)sulfonamides antibiotics can increase the activity of superoxide dismutase(SOD)and catalase(CAT)of intracellular antioxidant enzymes in Chlorella vulgaris and Microcystis aeruginosa,which indicates that excessive ROS is produced in the cell.When the concentration of sulfonamides antibiotics is too high,the intracellular antioxidant enzymes are not enough to remove the excessive ROS produced,so the growth of algal cells is seriouslyinhibited,and a large number of cells die due to the rupture of cell membrane.At this time,the intracellular SOD and CAT contents decrease significantly.(3)Sulfonamides can also increase the content of MDA in Chlorella vulgaris and Microcystis aeruginosa,which indicates that excessive ROS in algae cells leads to lipid peroxidation,which destroys the membrane of algae cells.(4)Sulfanilamide antibiotics have a great toxic effect on phytoplankton in water samples of reservoir,which significantly reduces the biomass,cell abundance and species of phytoplankton.At the same time,the sulfonamides resistance gene sul2 was induced,and the higher the concentration of sulfonamides,the higher the abundance of the resistance gene sul2.