Seguin F, LeBihan F, Leboulanger C, Berard A
Risk assessment, Aquatic mesocosm, Herbicide, Phytoplankton community tolerance, Fluorescence, mesocosm, Rennes, France, 5 m3
We investigated the validity and sensitivity of assessments of the induction of atrazine tolerance in freshwateroutdoor mesocosmic phytoplankton communities, using the in vivo fluorescence of chlorophyll a as an endpoint, formonitoring ecotoxicology and for risk assessment programs applied to phytoplankton contaminated by photosystem IIherbicides. Atrazine inhibits the photosynthetic process, and so the rise in in-vivo fluorescence could be used as aphysiological manifestation of acute toxicity. Short-term tests (1 h) were used, in which increasing concentrations of theherbicide were applied to phytoplankton samples taken every two days from the mesocosms, and used to plot dose–response curves. The concentration at which atrazine increased the fluorescence by 25% relative to control samples wasused to demonstrate the sensitivity of the phytoplankton, and the values found were compared for samples fromdifferent mesocosms (contaminated and non-contaminated). The taxonomic composition of the phytoplankton wasalso determined. The data showed that chronic exposure (25 days) to 30 mg/L of atrazine significantly increased theapparent tolerance of the phytoplankton to further contamination by the same compound. The use of in vivofluorescence of chlorophyll a appears to be a reliable and effective parameter for monitoring the effects of atrazinepollution, and detecting the changes in community tolerance driven by pollution selection pressure. r 2002 ElsevierScience Ltd. All rights reserved.