John Wiley & Sons, Ltd.

Secondary production of freshwater zooplankton communities exposed to a fungicide and to a petroleum distillate in outdoor pond mesocosms

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Ecological Risk Assessment (ERA) of chemicals in mesocosms requires measurement of a large number of parameters at community scale. Studies on invertebrate communities usually focus on taxonomic approaches which only provide insights into taxonomic structure changes induced by chemicals. In the present study, abundance, biomass (B), theoretical production (P) and instantaneous P/B ratio were used as endpoints to assess the effects of the commercial form of the dithiocarbamate fungicide thiram (35 and 170 µg/L nominal concentrations) and of the hydrocarbon water accommodated fraction (HWAF) of a petroleum distillate (0.01, 0.4, 2 and 20 mg/L loadings) on zooplankton community in freshwater pond mesocosms. Endpoints were measured during a 4‐week treatment period (one pulse per week) followed by a 5‐month post‐treatment period to evaluate zooplankton population recovery. Chlorophyll a concentration in water significantly increased after treatment to HWAF whereas it was not affected by thiram treatment. Zooplankton abundance‐based analysis showed effects on a limited number of taxa, whereas other endpoints (mainly P/B ratio) revealed that more taxa were impacted, with recovery depending on the chemical and concentration. HWAF exposure mainly had a negative impact on cladocerans which resulted in top‐down effects (between cladocerans and phytoplankton). Thiram negatively affected rotifers and copepods suggesting more direct toxic effects. Our results show that the use of secondary production as an endpoint provide a more comprehensive assessment of potential direct and indirect effects of chemicals on community and support evidence of alteration on functional processes. Environ Toxicol Chem © 2013 SETAC

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