title: Isotopic niche metrics as indicators of toxic stress in two freshwater snails.
abstract: Descriptors of trophic niche and of food web structure and function have been suggested as integrative and sensitive endpoints of toxicant effects. In the present study, carbon and nitrogen stable isotope signatures were used to assess the effects of the dithiocarbamate fungicide thiram (35 and 170μg/L nominal concentrations) and of a petroleum distillate (0.01, 0.4, 2 and 20mg/L nominal loadings as Hydrocarbon Emulsion or Hydrocarbon Water Accommodated Fraction) on the trophic niche of two freshwater gastropods in artificial streams (Radix peregra) and ponds (Lymnaea stagnalis). Results were analyzed using classical univariate statistical methods and recently proposed uni- and multivariate metrics of the realized trophic niche of species. The trophic niche metrics were highly sensitive to both types of chemicals, but exposure resulted in different response patterns according to the nature of the tested compound. Thiram clearly affected gastropod trophic niche leading to a change in the food resources used and resulting in trophic niche expansion (i.e., increase of diversity of used resources, especially dead animals) or trophic niche contraction (i.e., decrease of diversity of used resources) across time. Both gastropod taxa exposed to hydrocarbons showed a clear trophic niche expansion. Trophic niche metrics therefore provide a promising way of investigating non-lethal effects of exposure to organic chemicals on aquatic invertebrates, and subsequent disturbances in food webs.
authors.affiliation: INRA, UMR985 Écologie et Santé des Écosystèmes, Équipe Écotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Ouest, 65 rue de Saint Brieuc, F-35042 Rennes, France; Service Environnement, TOTAL SA, Pôle d'Etude et de Recherche de Lacq RN 117, BP 47, F-64170 Lacq, France.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Bayona
authors.affiliation: INRA, UMR985 Écologie et Santé des Écosystèmes, Équipe Écotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Ouest, 65 rue de Saint Brieuc, F-35042 Rennes, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Roucaute
authors.affiliation: Service Environnement, TOTAL SA, Pôle d'Etude et de Recherche de Lacq RN 117, BP 47, F-64170 Lacq, France.
authors.forename: Kevin
authors.initials: K
authors.lastname: Cailleaud
authors.affiliation: INRA, UMR985 Écologie et Santé des Écosystèmes, Équipe Écotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Ouest, 65 rue de Saint Brieuc, F-35042 Rennes, France. Electronic address: laurent.lagadic@rennes.inra.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Lagadic
authors.affiliation: Service Environnement, TOTAL SA, Pôle d'Etude et de Recherche de Lacq RN 117, BP 47, F-64170 Lacq, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Bassères
authors.affiliation: INRA, UMR985 Écologie et Santé des Écosystèmes, Équipe Écotoxicologie et Qualité des Milieux Aquatiques, Agrocampus Ouest, 65 rue de Saint Brieuc, F-35042 Rennes, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Caquet
mesh_terms: D000818:Animals; D004784:Environmental Monitoring / Q000379:methods*; D020387:Food Chain; D008195:Lymnaea; D045483:Rivers / Q000737:chemistry; D012908:Snails / Q000502:physiology; D013312:Stress, Physiological; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical
keywords: Artificial streams; Freshwater snails; Functional endpoints; Petroleum distillate; Pond mesocosms; Thiram