title: Structural changes in a macrozoobenthos assemblage after imidacloprid pulses in aquatic field-based microcosms.
abstract: A field-based microcosm experiment was performed to investigate the effects of repeated pulses of the neonicotinoid insecticide imidacloprid on a lentic benthos assemblage. This specific microcosm method was chosen because it allows for both testing of a wide range of organisms under natural conditions and as well as gaining insight into intraspecific and interspecific interactions. The macrozoobenthos that colonised the microcosms was exposed to three pulses each 1 week apart at nominal concentrations ranging from 0.6 to 40 μg/L. Imidacloprid underwent fast aqueous photolysis due to optimal sunlight conditions during the test phase (half-life = 28 ± 8 h [monitored for 21 days]). Nonetheless, decreased abundance and emergence of Ephemeroptera and decreased survival of chironomid species of the subfamilies Tanypodinae and Orthocladiinae were observed at time-weighted average concentrations of 2.3 μg/L. In contrast, the gastropod Radix sp. became dominant at high imidacloprid concentrations, probably due to decreased competition for food with sensitive species. The results of this study show that repeated short-term contamination of imidacloprid at low concentration levels may affect aquatic ecosystems even under optimal conditions for photodegradation. The microcosm approach, with its simple and field-relevant design, proved to be a useful tool for assessing the effects of imidacloprid contamination.
authors.affiliation: Department of Zoology, Centre for Aquatic Pollution Identification and Management (CAPIM), University of Melbourne, Melbourne, VIC, 3010, Australia, mcolombo@student.unimelb.edu.au.
authors.forename: Valentina
authors.initials: V
authors.lastname: Colombo
authors.forename: Silvia
authors.initials: S
authors.lastname: Mohr
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Berghahn
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Pettigrove
mesh_terms: D000818:Animals; D044822:Biodiversity; D002683:Chironomidae; D017753:Ecosystem; D007093:Imidazoles / Q000633:toxicity*; D007306:Insecticides / Q000633:toxicity*; D007448:Invertebrates / Q000145:classification* / Q000254:growth & development; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D014874:Water Pollutants, Chemical; C082359:imidacloprid