Effects Of Enrofloxacin On Nitrogen And Phosphorus Uptake Capacity Of Snailssubmerged Plant Complex Ecosystem And Its Mechanism

Quinolone antibiotics which is synthetic are all derived from the human factors in nature.With the rapid and vigorous development of aquaculture and livestock farming in recent years,farming density is getting higher and higher,and the prevention and control of infectious diseases is particularly important.In order to prevent the outbreak of infectious diseases,many farmers will regularly use antibiotics for disease prevention,which is represented by enrofloxacin(ENR).After the residual antibiotics enter the natural water body,which will have a certain impact on the organisms in the water body,especially the microorganisms,and the nanogram level of quinolone antibiotic drugs in the environment can induce the emergence of antibacterial drugs.The snails-submerged plant ecosystem is a complex ecosystem composed of sails,submerged plants and periphyton,which has a strong absorption and purification effect on nitrogen and phosphorus in the water body,and the main body of which purifies nitrogen and phosphorus is the periphyton.However,the light will be blocked to inhibit the growth of submerged plants when periphyton grow too much since they are very dependent on light.A moderate amount of snail can inhibit the growth of periphyton,thereby promoting the growth of submerged plants.When there are too few periphyton,the system’s ability to purify water may be reduced.Therefore,the snails,Vallisneria natans,and periphyton interact in nature and are in a dynamic balance.The discharge of antibiotics may affect the periphyton first,thereby affecting the purification capacity of the entire system.The Sinotaia aeruginosa and V.natans are widely distributed species and the most used materials in ecological restoration.In this experiment,S.aeruginosa,V.natans and their foliar attached organisms were used as the research objects,and the effect of enrofloxacin on the absorption capacity of nitrogen and phosphorus in the snails-submerged plant complex ecosystem was systematically studied.The results of the study are as follows:(1)With the increase of the snails-submerged plant ratio,periphyton on the leaves of V.natans decreased significantly,at the same time,the Chl a content in the water layer also decreased.The relative growth amount and the number of ramets increased correspondingly,when the snails-submerged plant ratio was 0.078.However,when the snails-submerged plant ratio continued to increase,the growth of V.natans will be suppressed.(2)Nanogram-level ENR can inhibit the absorption of phosphorus input by pulse,and the inhibitory effect is enhanced with the increase of ENR concentration.At the same time,periphyton,epiphytic organic mass and epiphytic algal chlorophyll are decreased with the increase of ENR concentration.And the structure of the epiphytic community also changed significantly,indicating that this inhibitory effect was mainly achieved by reducing periphyton,changing the structure of the epiphytic community,and inhibiting photosynthesis.(3)The snails-submerged plant-periphyton ecosystem has a certain tolerance to enrofloxacin.Nanogram-level ENR can also inhibit the system’s absorption of phosphorus in water,but the inhibition effect of the highest concentration is relatively weak,nanogram-level ENR also inhibits the absorption of nitrate.But with the increase of time,the inhibition.The smaller the effect;ENR hardly inhibited the chlorophyll of epiphytic algae,and because of ENR inhibited the activity of snails,its food intake reduced,and periphyton increased with the increase of ENR concentration.In summary,nanogram level of enrofloxacin can cause changes in the snailssubmerged plant-periphyton complex system,which affects its ability to absorb and purify nitrogen and phosphorus nutrients.The research results provide a scientific basis for antibiotic pollution and prevention.