Distribution Characteristics Of Two Types Of Antibiotic Resistance Genes In Taihu Lake In Winter

In recent decades,antibiotics and antibiotic resistance genes（ARGs）have become new pollutant in lakes due to the large use of antibiotics in livestock,poultry and aquatic products,resulting in a large increase in the contents of antibiotics and ARGs in lakes.In this thesis,the spatial distribution two common antibiotics（sulfonamides and tetracyclines）and their correspnding ARGs（sulfonamides:sul1,sul2 and sul3;tetracyclines:tetO and tetW）in water and sediment of Taihu Lake in winter were studied.The different distribution of ARGs in water and sediment were compared,and the correlation between ARGs and environmental factors,for example water quality parameters,heavy metal concentration and antibiotic concentration was analyzed.At the end,the risk coefficient of antibiotic contamination in shallow eutrophic Lake Taihu was preliminarily evaluated.The main results were as follows:1.In Lake Taihu,the concentration of sulfamide（mean 65.46ng/L）was higher than those of tetracyclines（mean 35.78ng/L）in water column.The enriched area of the two antibiotics were found in Zhushan Bay,Dapu estuary and Gonghu Bay.The sulfamide concentrations in sediments（mean 0.15 ng/g dry weight）were lower than tetracyclines（mean1.99ng/g dry weight）.The enriched sediments of sulfamide were found in Zhushan Bay and Dapu estuary.And the enriched sediment of tetracycline were found in Zhushan Bay,Dapu estuary,Meiliang Bay and Wuli Lake.The risk assessment of antibiotic pollution in Lake Taihu showed that sulfamethoxazole（SMX）had a moderate risk in water column（0.1<RQ<1）.Tetracycline（CTC）and polytetracycline（DC）had high risk（RQ>1）,while oxytetracycline（OTC）had a moderate risk（0.1<RQ<1）.2.In Lake Taihu,sulfonamide ARGs was more abundant than tetracycline ARGs both in water and sediment.The concentration of three sulfonamide ARGs types has the order sul1>sul2>sul3,and tetracycline ARGs has the order tetO>tetW.Sul1 and sul2 were accumulated in the water column of Zhushan Bay,Dapu estuary and Meiliang Bay.Sul1 was more abundant in sediment of Meiliang Bay,Wuli Lake and Gonghu Bay Lake and sul2 was mainly found in Meiliang Bay,Zhushan Bay and Dapu estuary.Tetracycline ARGs tetO and tetW were mainly found in Dapu estuary and Zhushan Bay.3.Significantly positive correlations between ARGs sul1 and sulfamides,as well as tetO and tetracyclines were detected both in water and sediment of Taihu Lake.Moreover different accumulation pattern of sulfonamide ARGs and tetracycline ARGs was promopted.The normalized contents of sul1 and sul3（abusolte concentration of ARGs normolzied by the 16S rRNA gene copies）in water phase were significantly higher than those in sediment（P<0.05）.No distribution preference between water and sediment were detetcd for the normazlied tetO and tetW（P>0 05）.4.Significant positive correlation between ARGs sul1 and sul2 with many physicochemical factors,such as COD,TP,TN and NH4-N（P<0.05）was detetctd in water.Negative correlation between tetO and pH,dissolved oxygen was identified（P<0.05）.The changes of physical and chemical environment in water can significantly affect the spatial distribution of ARGs.It can be expected that the higher nutrient concentration in lake could cause the accumulation of ARGs.5.Metal ions such as Ca²⁺,Mg²⁺,Na⁺and Si⁴⁺has a significant positive correlation with ARGs,which indicated that the presence of metal ions might affect the distribution of ARGs.In summary,spatial distribution pattern of antibiotics（sulfonamides and tetracyclines）and their corresponding ARGs in Taihu Lake studied in detail,and the main environmental factors affecting their content and distribution were revealed.The risk of antibiotic pollution in Taihu Lake in winter was evaluated.The results could be helpful for understanding the current situation of antibiotic pollution in Taihu Lake,also provide basic informaiton for targeted pollution prevention and control.