title: Lethal/sublethal responses of Daphnia magna to acute norfloxacin contamination and changes in phytoplankton-zooplankton interactions induced by this antibiotic.
abstract: Although the well-known antibiotic norfloxacin (NOR) is recognized as an important environmental pollutant, little is known about its impacts on ecological processes, particularly on species interactions. In this paper, we quantified Daphnia magna (Crustacea, Cladocera) responses in mortality rate at lethal NOR concentrations (0, 25, 50, 100, 200, 300 and 400 mg L-1), and in heartbeat rate, swimming behavior and feeding rate (on the green alga Chlorella pyrenoidosa) at sublethal NOR concentrations (0, 25, 50 and 100 mg L-1) to determine the effects of this antibiotic in plankton systems. In 96-h-long lethal experiment, mortality rates of D. magna increased significantly with increasing NOR concentration and exposure time. In sublethal experiments, heartbeat rate decreased, while time ratio of vertical to horizontal swimming (TVH) and the duration of quiescence increased in D. magna individuals exposed to increasing NOR concentrations after 4 and 12 h of exposure. These collectively led to decreases in both average swimming ability and feeding rate, consistent with the positive relationship between average swimming ability and feeding rate. Overall, results indicate that, by affecting zooplankton heartbeat rate and behavior, NOR decreased feeding efficiency of D. magna even at low doses, therefore, it might seriously compromise ecosystem health and function.
authors.affiliation: School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Pan
authors.affiliation: School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China.
authors.forename: Shi-Wei
authors.initials: SW
authors.lastname: Yan
authors.affiliation: School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China.
authors.forename: Ruo-Zhu
authors.initials: RZ
authors.lastname: Li
authors.affiliation: Department of Biology, Yunnan University, Kunming 650091, China.
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Hu
authors.affiliation: School of Ecology and Environmental Sciences, Yunnan University, Kunming 650091, China.
authors.forename: Xue-Xiu
authors.initials: XX
authors.lastname: Chang
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D003621:Daphnia / Q000187:drug effects / Q000502:physiology*; D005247:Feeding Behavior / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D020128:Inhibitory Concentration 50; D009643:Norfloxacin / Q000633:toxicity*; D010839:Phytoplankton / Q000187:drug effects / Q000502:physiology*; D013550:Swimming; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015048:Zooplankton / Q000187:drug effects / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D009643:Norfloxacin