title: Use of polar organic chemical integrative samplers to assess the effects of chronic pesticide exposure on biofilms.
abstract: The responses of aquatic organisms to chronic exposure to environmental concentrations of toxicants, often found in mixtures, are poorly documented. Here passive sampler extracts were used in experimental contamination of laboratory channels, to investigate their effects on natural biofilm communities. A realistic mixture of pesticides extracted from Polar Organic Chemical Integrative Samplers was used to expose biofilms in laboratory channels to total pesticide concentrations averaging 0.5 ± 0.1 μg l⁻¹. The level of exposure was representative of field conditions in terms of relative proportions of the substances but the exposure concentration was not maintained (decreasing concentrations between contamination occasions). The impact on the structural as well as the functional characteristics of the autotrophic and heterotrophic components was determined, using biofilm grown in uncontaminated conditions (reference site) and in sites exposed to pesticides (contaminated site). The exposure imposed did not significantly modify the structure or functions of reference biofilms, nor did it modify tolerance as measured by mixture EC₅₀ (EC₅₀ mix). In contrast, the communities from the more contaminated downstream section lost tolerance following decreased dose exposure, but community composition remained fairly stable. Overall, these results indicate that low levels of contamination did not lead to strong changes in community structure, and 14-day changes in tolerance seemed to depend mainly on physiological adaptation, suggesting that other environmental factors or longer-lasting processes prevailed. This study reports the first attempt to use passive sampler extracts as a realistic composite contaminant for experimental exposure of biofilms, with promising perspectives in further ecotoxicology studies.
authors.affiliation: Irstea, UR REBX, 50 Avenue de Verdun, 33612 Cestas Cedex, France. soizic.morin@irstea.fr
authors.forename: Soizic
authors.initials: S
authors.lastname: Morin
authors.forename: Stéphane
authors.initials: S
authors.lastname: Pesce
authors.forename: Sandra
authors.initials: S
authors.lastname: Kim-Tiam
authors.forename: Xavier
authors.initials: X
authors.lastname: Libert
authors.forename: Marina
authors.initials: M
authors.lastname: Coquery
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mazzella
mesh_terms: D052818:Autotrophic Processes / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D017753:Ecosystem; D054750:Ecotoxicology; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D052836:Heterotrophic Processes / Q000187:drug effects; D009930:Organic Chemicals / Q000737:chemistry / Q000633:toxicity*; D010575:Pesticides / Q000737:chemistry / Q000633:toxicity*; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000633:toxicity*
chemical_list: D009930:Organic Chemicals; D010575:Pesticides; D014874:Water Pollutants, Chemical