Adapting an enzymatic toxicity test to allow comparative evaluation of natural freshwater biofilms’ tolerance to metals
|Title||Adapting an enzymatic toxicity test to allow comparative evaluation of natural freshwater biofilms’ tolerance to metals|
|Publication Type||Journal Article|
|Year of Publication||2010|
|Authors||Fechner LC, Gourlay-Francé C, Uher E, Tusseau-Vuillemin M-H|
|Pagination||1302 - 1311|
|Keywords||Enzymatic activity, Metal tolerance, Periphyton, Short-term toxicity test|
A simple, low-cost and non-radioactive short-term toxicity test was developed to study the effects of urban metals on natural freshwater periphytic communities. ß-glucosidase activity of natural freshwater biofilms collected in situ was chosen as an endpoint. Metals (Cd, Cu, Ni, Pb, and Zn) successfully inhibited bacterial enzymatic activity after a 1-h exposure enabling the calculation of EC50. The EC50 value of a biofilm sample varied with the Total Suspended Solids concentration (TSS) of the biofilm suspension, showing that EC50 values (expressed as total added metal concentrations) are not representative of the bioavailable metal concentration during the toxicity test. For Cu, Cd, Ni, Zn and Pb, the EC50 values increased linearly with the TSS concentration leading us to define a normalized EC50: the value of the EC50 divided by the corresponding TSS concentration. Normalized EC50 proved to be a robust, reliable way to assess metal tolerance of a biofilm for Cd, Cu, Ni, Zn and Pb. Normalized EC50 obtained, expressed as kgmetal/gTSS, varied between 0.2 to 7.6 for Cu, 1 to 8 for Cd, 1.8 to 92.3 for Ni, 1.8 to 76.6 for Zn and 25 to 189 for Pb.