Antibiotic resistance genes and their links with bacteria and environmental factors in three predominant freshwater aquaculture modes.

Rapid development of aquaculture industry and increasing demand of various inputs (especially antibiotics), are suspected to promote the occurrence and spread of ARGs in aquaculture related environments. However, the occurrences of ARGs under different freshwater aquaculture practices are rarely known. Here, we investigated the seasonal profiles of the main ARGs, intI 1 and bacteria in waters from three kinds of predominant freshwater aquaculture practices around the Honghu Lake (China), as well as their co-occurrences and interrelationships with antibiotics, heavy metals and general water quality. The results indicate that quinolone resistance genes (qnr B), tetracycline resistance genes (tet B and tet X) and sulfonamide resistance genes (sul 1 and sul 2) were the top five predominant ARGs with seasonal variations of abundance. Fish ponds were of the highest absolute abundances of tested ARGs than the other two modes. Crayfish ponds and their adjacent ditches shared similar ARGs profile. Different subtypes of ARGs belonging to the same class of resistance were varied in abundances. Some bacteria were predicted to carry different ARGs, which indicating multi-antibiotic resistances. Moreover, the combined environmental factors (antibiotics, heavy metals and water quality) partially shaped the profiles of ARGs and bacteria composition. Overall, this study provides new comprehensive understanding on the characterization of ARGs contamination in different freshwater aquaculture practices from the perspectives of environmental chemistry, microbiology and ecology. The results would benefit the optimization of aquaculture practices toward environmental integrity and sustainability. [Display omitted] • ARGs were measured in three main aquaculture modes and adjacent ditches and a lake. • Predominant ARGs were qnr B, tet B, tet X, sul 1 and sul 2 in target aquaculture ponds. • Fish ponds were under higher abundances of multiple ARGs in water than the others. • Multi-antibiotic resistance and different abundance among ARGs subtypes were observed. • Antibiotics, heavy metals and water quality partially shaped occurrences of ARGs. [ABSTRACT FROM AUTHOR]