Second-, third- and fourth-generation quinolones: Ecotoxicity effects on Daphnia and Ceriodaphnia species

We conducted the first complete toxicological study of six quinolones, including acute, chronic, and recovery assays on Daphnia magna and Ceriodaphnia dubia. The assayed quinolones were second-generation ciprofloxacin (CIP), norfloxacin (NOR), enrofloxacin (ENR), and marbofloxacin (MAR); third-generation levofloxacin (LEV), and fourth-generation moxifloxacin (MOX). The median lethal concentrations (LC50) obtained for both species by acute ecotoxicity assay ranged from 14 to 73 mg L^-1 and from 3 to 23 mg L^-1 at 48 and 72 h, respectively; while the median effective concentration (EC50) ranged from 4 to 28 mg L^-1 in the chronic ecotoxicity assays. C. dubia surviving the chronic exposure assay was monitored in recovery assays free of quinolones. A fluorometric method was used to confirm that there was no significant loss of quinolone concentrations during the acute assays. We also used this method to show that quinolone concentrations fell below 80% of the nominal value after 9-11 d if exposure solutions were not renewed. This study on the ecotoxicological and chemical behavior of quinolones in two cladoceran species fills a data gap about how these emerging contaminants affect nontarget aquatic organisms and how long they persist in the environment.