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  • Title: A risk assessment of pollution: induction of atrazine tolerance in phytoplankton communities in freshwater outdoor mesocosms, using chlorophyll fluorescence as an endpoint.
    Author: Seguin F, Le Bihan F, Leboulanger C, Bérard A.
    Journal: Water Res; 2002 Jul; 36(13):3227-36. PubMed ID: 12188119.
    Abstract:
    We investigated the validity and sensitivity of assessments of the induction of atrazine tolerance in freshwater outdoor mesocosmic phytoplankton communities, using the in vivo fluorescence of chlorophyll a as an endpoint, for monitoring ecotoxicology and for risk assessment programs applied to phytoplankton contaminated by photosystem II herbicides. Atrazine inhibits the photosynthetic process, and so the rise in in-vivo fluorescence could be used as a physiological manifestation of acute toxicity. Short-term tests (1 h) were used, in which increasing concentrations of the herbicide 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 was used to demonstrate the sensitivity of the phytoplankton, and the values found were compared for samples from different mesocosms (contaminated and non-contaminated). The taxonomic composition of the phytoplankton was also determined. The data showed that chronic exposure (25 days) to 30 microg/L of atrazine significantly increased the apparent tolerance of the phytoplankton to further contamination by the same compound. The use of in vivo fluorescence of chlorophyll a appears to be a reliable and effective parameter for monitoring the effects of atrazine pollution, and detecting the changes in community tolerance driven by pollution selection pressure.
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