title: Effects of the antibiotic enrofloxacin on the ecology of tropical eutrophic freshwater microcosms.
abstract: The main objective of the present study was to assess the ecological impacts of the fluoroquinolone antibiotic enrofloxacin on the structure and functioning of tropical freshwater ecosystems. Enrofloxacin was applied at a concentration of 1, 10, 100 and 1,000 μg/L for 7 consecutive days in 600-L outdoor microcosms in Thailand. The ecosystem-level effects of enrofloxacin were monitored on five structural (macroinvertebrates, zooplankton, phytoplankton, periphyton and bacteria) and two functional (organic matter decomposition and nitrogen cycling) endpoint groups for 4 weeks after the last antibiotic application. Enrofloxacin was found to dissipate relatively fast from the water column (half-dissipation time: 11.7h), and about 11% of the applied dose was transformed into its main by-product ciprofloxacin after 24h. Consistent treatment-related effects on the invertebrate and primary producer communities and on organic matter decomposition could not be demonstrated. Enrofloxacin significantly affected the structure of leaf-associated bacterial communities at the highest treatment level, and reduced the abundance of ammonia-oxidizing bacteria and ammonia-oxidizing archaea in the sediments, with calculated NOECs of 10 and <1 μg/L, respectively. The ammonia concentration in the microcosm water significantly increased in the highest treatment level, and nitrate production was decreased, indicating a potential impairment of the nitrification function at concentrations above 100 μg/L. The results of this study suggest that environmentally relevant concentrations of enrofloxacin are not likely to result in direct or indirect toxic effects on the invertebrate and primary producer communities, nor on important microbially mediated functions such as nitrification.
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands. Electronic address: andreu.rico@wur.nl.
authors.forename: Andreu
authors.initials: A
authors.lastname: Rico
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Laboratory of Microbiology, Wageningen University, Wageningen University and Research Centre, Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Mauricio R
authors.initials: MR
authors.lastname: Dimitrov
authors.affiliation: Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: René P A
authors.initials: RP
authors.lastname: Van Wijngaarden
authors.affiliation: Department of Fishery Biology, Faculty of Fisheries, Kasetsart University, Chatuchak, 10900 Bangkok, Thailand.
authors.forename: Kriengkrai
authors.initials: K
authors.lastname: Satapornvanit
authors.affiliation: Laboratory of Microbiology, Wageningen University, Wageningen University and Research Centre, Dreijenplein 10, 6703 HB Wageningen, The Netherlands.
authors.forename: Hauke
authors.initials: H
authors.lastname: Smidt
authors.affiliation: Department of Aquatic Ecology and Water Quality Management, Wageningen University, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Van den Brink
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D001419:Bacteria / Q000187:drug effects*; D017753:Ecosystem; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000633:toxicity*; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology; D007448:Invertebrates / Q000187:drug effects*; D010933:Plankton / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D060753:Water Quality
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D014874:Water Pollutants, Chemical; D000077422:Enrofloxacin
keywords: Antibiotics; Ecological risk assessment; Enrofloxacin; Microcosms; Tropics