Response of biofilm bacterial communities to antibiotic pollutants in a Mediterranean river

► We studied the effects of antibiotics detected in river waters on biofilm communities. ► Biofilm switch to more polluted waters evidenced responses of bacteria communities. ► Bacteria mortality increased and enzymes activity decreased in switched biofilms. ► Actinobacteria abundance increased in switched biofilms. ► Biofilm bacteria responses showed significant correlation with antibiotic levels.