| China has a vast ocean area,and the aquaculture industry plays an important role in China’s industrial economy.The overuse of antibiotics in mariculture exacerbates selective pressures on microorganisms in the environment.Long-term repeated use of antibiotics will not only lead to drug resistance of organisms,but also may induce microorganisms to produce antibiotic resistant genes（ARGs）,which will damage the stability of microorganisms in situ and cause new environmental pollution.In recent years,most of the studies on the distribution of antibiotic resistance genes and microbial diversity in Marine areas have focused on the northern and eastern coastal waters.As an important mariculture province in China,Hainan province has several lagoonal bays,so it is necessary to study the distribution of antibiotic resistance genes and microbial diversity in the main lagoonal mariculture areas.This study focused on Wanning and Lingshui lagoonal mariculture areas mariculture zones in southeast Hainan Province,and collected surface seawater samples from 8 sample sites.Liquid chromatography tandem mass spectrometry（LC-MS/MS）was used to detect antibiotic residues in seawater.Quantitative real-time Quantitative PCR（q PCR）was used to quantify antibiotic resistance genes,and high-throughput sequencing was used to study microbial diversity.Through the correlation analysis of resistance genes with major environmental factors and microbial communities,the possible sources of resistance genes were revealed,so as to understand the current situation of antibiotic residues and ARGs pollution in lagoonal mariculture zones in southeast Hainan,and to provide scientific reference for environmental protection and management of mariculture zones.The main results are as follows:（1）A total of 11 antibiotics of three types were detected in the study area,including no sulfonamides,6 quinolones（SAR,ENO,CIN,ENR,CIP,OFL）,3 tetracyclines（TC,DOC,CTC）and 2 chloramphenicol antibiotics（CHP,FLO）.Among the three types of antibiotics,quinolones had the highest content(65.42 ng·L-1),followed by tetracycline antibiotics(29.92 ng·L-1),and chloramphenicol antibiotics had the lowest content(5.52 ng·L-1).The concentration of antibiotic residues in the study area ranged from 14.93 ng·L-1 to 259.75ng·L-1,among which S1（Wanning）was the highest and S5（Xincun）the lowest.Compared with similar studies,the antibiotic residues in the seawater measured were at a lower level.Antibiotic residues were correlated with environmental factors to some extent.（2）The use of q PCR to quantitative analysis of the ARGs,were detected with nine goals ARGs and 1 kind of integron genes intⅠ1.Relative abundance of target gene orders of magnitude for the 10-6-10-1copies/16sr RNA,in which the highest is tet G(1.63×10-3-1.11×10-1copies/16Sr RNA),the second is sul2(1.20×10-3-5.23×10-2 copies/16Sr RNA),intⅠ1(1.36×10-3-8.60×10-3copies/16Sr RNA)detection of the third,the relative abundance peak for the S4.IntⅠ1 abundance was significantly positively related to five ARGs,promote the horizontal gene transfer of those ARGs.（3）A total of 74 phyla,162 classes,373 orders,525 families and 902 genera were identified by high-throughput sequencing.Proteobacteria was the main microbial community at the phylum level,accounting for 67.03%,while Vibrio was the main microbial community at the genus level,accounting for 21.37%.The distribution of dominant microbial community in different sampling sites showed certain differences.（4）By analyzing the correlation between microbial diversity and environmental factors,the results showed that ammonium salt and salinity were the main environmental factors affecting the distribution of microbial diversity,which had significant relationship with 9 microbial groups in the top 20 phyla.Correlation analysis was carried out on the ARGs and microorganisms found in phyla level,tetracycline resistant genes tet C were significant correlation with 22 kinds of microbes,chloramphenicol resistance genes cmle1were significant correlation with four kinds of microbes,sulfonamides resistance gene sul1exists significant correlation with 6 kinds of microbes and indirectly reflects those ARGs had wide host source than other genes.Fusobacteriota and Modulibacteria were the main potential hosts of ARGs in the seawater of the sampling area. |
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