title: Comparative responses of river biofilms at the community level to common organic solvent and herbicide exposure.
abstract: Residual pesticides applied to crops migrate from agricultural lands to surface and ground waters. River biofilms are the first aquatic non-target organisms which interact with pesticides. Therefore, ecotoxicological experiments were performed at laboratory scale under controlled conditions to investigate the community-level responses of river biofilms to a chloroacetanilide herbicide (alachlor) and organic solvent (methanol) exposure through the development referenced to control. Triplicate rotating annular bioreactors, inoculated with river water, were used to cultivate river biofilms under the influence of 1 and 10 μg L(-1) of alachlor and 25 mg L(-1) of methanol. For this purpose, functional (thymidine incorporation and carbon utilization spectra) and structural responses of microbial communities were assessed after 5 weeks of development. Structural aspects included biomass (chlorophyll a, confocal laser scanning microscopy) and composition (fluor-conjugated lectin binding, molecular fingerprinting, and diatom species composition). The addition of alachlor resulted in a significant reduction of bacterial biomass at 1 μg L(-1), whereas at 10 μg L(-1), it induced a significant reduction of exopolymer lectin binding, algal, bacterial, and cyanobacterial biomass. However, there were no changes in biofilm thickness or thymidine incorporation. No significant difference between the bacterial community structures of control and alachlor-treated biofilms was revealed by terminal restriction fragment length polymorphism (T-RFLP) analyses. However, the methanol-treated bacterial communities appeared different from control and alachlor-treated communities. Moreover, methanol treatment resulted in an increase of bacterial biomass and thymidine incorporation as well. Changes in dominant lectin binding suggested changes in the exopolymeric substances and community composition. Chlorophyll a and cyanobacterial biomass were also altered by methanol. This study suggested that the concentration-dependent effect of alachlor mainly remains limited to biomass and growth inhibition without apparent changes of structural and functional characteristics measured. Our work also establishes the potential toxic effects of organic solvents on river biofilm in ecotoxicological experiments. For the ecotoxicological experiments, the alternative of dissolution in organic solvent followed by its evaporation, depositing the chemical on a glass surface prior to dissolution in river water used here, appears to allow exposure while minimizing the effect of organic solvent.
authors: EcoLab (Laboratoire d'écologie fonctionnelle et environnement), Université de Toulouse, UPS, INP, 118 route de Narbonne, 31062, Toulouse, France. arps1284@gmail.com.|CNRS, EcoLab, 31062, Toulouse, France. arps1284@gmail.com.
authors: A
authors: A
authors: Paule
authors: IRSTEA, UR EABX, Equipe de Recherche CARMA, 50 avenue de Verdun, 33612, Cestas, France.
authors: V
authors: V
authors: Roubeix
authors: Environment Canada, Saskatoon, SK, Canada.
authors: G D W
authors: GD
authors: Swerhone
authors: Environment Canada, Saskatoon, SK, Canada.
authors: J
authors: J
authors: Roy
authors: Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux - IPREM, UMR 5254 CNRS/UPPA, IBEAS, Université de Pau et des Pays de l'Adour, BP1155, 64013, Pau, France.
authors: B
authors: B
authors: Lauga
authors: Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l'Environnement et les Matériaux - IPREM, UMR 5254 CNRS/UPPA, IBEAS, Université de Pau et des Pays de l'Adour, BP1155, 64013, Pau, France.
authors: R
authors: R
authors: Duran
authors: IRSTEA, UR EABX, Equipe de Recherche CARMA, 50 avenue de Verdun, 33612, Cestas, France.
authors: F
authors: F
authors: Delmas
authors: Université de Toulouse, INSA, LISBP, 135 Avenue de Rangueil, 31077, Toulouse, France.|INRA, UMR792, Ingénierie des Systèmes Biologiques et des Procédés, 31400, Toulouse, France.|CNRS, UMR5504, 31400, Toulouse, France.
authors: E
authors: E
authors: Paul
authors: EcoLab (Laboratoire d'écologie fonctionnelle et environnement), Université de Toulouse, UPS, INP, 118 route de Narbonne, 31062, Toulouse, France.|CNRS, EcoLab, 31062, Toulouse, France.
authors: J L
authors: JL
authors: Rols
authors: Environment Canada, Saskatoon, SK, Canada.
authors: J R
authors: JR
authors: Lawrence
mesh_terms: D000081:Acetamides / Q000633:toxicity; D018441:Biofilms / Q000254:growth & development*; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D058448:Biota / Q000187:drug effects*; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000187:drug effects / Q000378:metabolism; D017377:Diatoms / Q000187:drug effects / Q000378:metabolism; D006540:Herbicides / Q000633:toxicity*; D000432:Methanol / Q000633:toxicity; D045483:Rivers / Q000737:chemistry / Q000382:microbiology; D012997:Solvents / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000081:Acetamides; D006540:Herbicides; D012997:Solvents; D014874:Water Pollutants, Chemical; D002734:Chlorophyll; C000188:alachlor; D000432:Methanol; D000077194:Chlorophyll A
keywords: Community level; Confocal microscopy; Herbicide response; Molecular analysis; Organic solvent; Rotating annular bioreactor; T-RFLP