Mercury toxicity to freshwater organisms: extrapolation using species sensitivity distribution

Mercury toxicity to aquatic organisms was evaluated in different taxonomic groups showing the following species sensitivity gradient: Daphnia magna > Daphnia longispina > Pseudokirchneriella subcapitata > Chlorella vulgaris > Lemna minor > Chironomus riparius. Toxicity values ranged from 3.49 μg/L (48 h-EC₅₀ of D. magna) to 1.58 mg/L (48 h-EC₅₀ of C. riparius). A species sensitivity distribution was used to estimate hazardous mercury concentration at 5 % level (HC5) and the predicted no effect concentration (PNEC). The HC5 was 3.18 μg Hg/L and the PNEC varied between 0.636 and 3.18 μg Hg/L, suggesting no risk of acute toxicity to algae, plants, crustaceans and insects in most freshwaters.We thank João Pedrosa, Tânia Vidal and Abel Ferreira (Department of Biology of the University of Aveiro) for providing C. riparius, L. minor cultures and algae cultures, respectively. The Portuguese Foundation for Science and Technology (FCT) supported the Post-doctoral fellowship SFRH/BPD/45807/2008 and CAPES- FCT 240/09 and the doctoral fellowship SFRH/BD/ 27637/2006.publishe