title: Antibiotic mixture effects on growth of the leaf-shredding stream detritivore Gammarus fossarum.
abstract: Pharmaceuticals contribute greatly to human and animal health. Given their specific biological targets, pharmaceuticals pose a significant environmental risk by affecting organisms and ecosystem processes, including leaf-litter decomposition. Although litter decomposition is a central process in forest streams, the consequences of exposure to pharmaceuticals remain poorly known. The present study assessed the impact of antibiotics as an important class of pharmaceuticals on the growth of the leaf-shredding amphipod Gammarus fossarum over 24 days. Exposure scenarios involved an antibiotic mixture (i.e. sulfamethoxazole, trimethoprim, erythromycin-H2O, roxithromycin, clarithromycin) at 0, 2 and 200 µg/L to assess impacts resulting from exposure to both water and food. The antibiotics had no effect on either leaf-associated fungal biomass or bacterial abundance. However, modification of leaf quality (e.g. through shifts in leaf-associated microbial communities) may have triggered faster growth of gammarids (assessed in terms of body mass gain) at the low antibiotic concentration relative to the control. At 200 µg/L, however, gammarid growth was not stimulated. This outcome might be due to a modified ability of the gut microflora to assimilate nutrients and carbon. Furthermore, the observed lack of increases in the diameter of the gammarids' peduncles, despite an increase in gammarid mass, suggests antibiotic-induced effects in the moulting cycle. Although the processes responsible for the observed effects have not yet been identified, these results suggest a potential role of food-quality, gammarid gut microflora and alteration in the moulting cycle in mediating impacts of antibiotics on these detritivores and the leaf decomposition process in streams.
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Landau Campus, Fortstrasse 7, 76829, Landau, Germany. mirco.bundschuh@slu.se.|Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Box 7050, 75007, Uppsala, Sweden. mirco.bundschuh@slu.se.
authors.forename: Mirco
authors.initials: M
authors.lastname: Bundschuh
authors.affiliation: Fraunhofer Institute for Toxicology and Experimental Medicine, Nikolai-Fuchs-Strasse 1, 30625, Hannover, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Hahn
authors.affiliation: Department of Experimental Limnology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Alte Fischerhütte 2, 16775, Stechlin, Germany.|Department of Ecology, Berlin Institute of Technology (TU Berlin), Ernst-Reuter-Platz 1, 10587, Berlin, Germany.
authors.forename: Mark O
authors.initials: MO
authors.lastname: Gessner
authors.affiliation: Institute for Environmental Sciences, University of Koblenz-Landau, Landau Campus, Fortstrasse 7, 76829, Landau, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Schulz
mesh_terms: D033304:Amphipoda / Q000502:physiology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D017753:Ecosystem; D005247:Feeding Behavior / Q000187:drug effects*; D018515:Plant Leaves; D045483:Rivers; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical
keywords: Food quality; Gammarus fossarum; Indirect effect; Leaf-associated microbial community; Physiological fitness