title: Variations of periphytic diatom sensitivity to the herbicide diuron and relation to species distribution in a contamination gradient: implications for biomonitoring.
abstract: Diatoms are commonly used as bioindicators of trophic and saprobic pollution in rivers. However, more knowledge is needed concerning their sensitivity to toxicants such as agricultural herbicides. In this study, seven species of periphytic diatoms were isolated from the Morcille River (Beaujolais area, France) which presents a streamward contamination gradient by pesticides and particularly diuron. The sensitivity of these species to diuron was assessed through ecotoxicological tests based on short-term growth inhibition of monospecific cultures. After application of an appropriate toxicological model, EC50 were determined and the species were ranked according to their tolerance. EC50 values ranged from 4.5 to 19 μg L(-1). Finally, the results were related to field periphyton samples from an upstream and a downstream site in order to check if variations in specific relative abundance between sites are consistent with differences in tolerance to diuron. Species distribution between sites was only partially in accordance with toxicological results suggesting that other factors (toxic or trophic) have an important influence on diatom communities in the river. Nevertheless, diatoms showed their potential to indicate water contamination by pesticides and toxic indices could be developed in complement to existing trophic indices.
authors.affiliation: Cemagref, UR REBX, F-33612 Cestas Cedex, France. vincent.roubeix@cemagref.fr
authors.forename: Vincent
authors.initials: V
authors.lastname: Roubeix
authors.forename: Nicolas
authors.initials: N
authors.lastname: Mazzella
authors.forename: Laurie
authors.initials: L
authors.lastname: Schouler
authors.forename: Vincent
authors.initials: V
authors.lastname: Fauvelle
authors.forename: Soizic
authors.initials: S
authors.lastname: Morin
authors.forename: Michel
authors.initials: M
authors.lastname: Coste
authors.forename: François
authors.initials: F
authors.lastname: Delmas
authors.forename: Christelle
authors.initials: C
authors.lastname: Margoum
mesh_terms: D017377:Diatoms / Q000187:drug effects*; D004237:Diuron / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004784:Environmental Monitoring / Q000379:methods; D006540:Herbicides / Q000633:toxicity*; D045483:Rivers / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D004237:Diuron