Effects of copper and cadmium on cholinesterase and glutathione S-transferase activities of two marine gastropods (Monodonta lineata and Nucella lapillus)

With the view of using Nucella lapillus and Monodonta lineata as bioindicators in biomonitoring programs in the NW coast of Portugal, the sensitivity to copper and cadmium of these two common species in Atlantic coasts of Europe was investigated. Assays based on mortality and on the activity of the enzymes cholinesterases (ChE) and glutathione S-transferases (GST) were used, as these biomarkers have been used in biomonitoring studies in the area. ChEs present in foot muscle of both species were characterised and found to show properties of both typical acetylcholinesterase and pseudocholinesterase. Cadmium LC50s for N. lapillus and M. lineata were 2.64 and 2.44 mg/L, respectively, while the lowest observed effect concentration (LOEC) was 1.53 mg/L for both species. LOEC value for cooper was 0.075 mg/L for both. Cadmium in vivo exposure increased ChE activity of N. lapillus, but had no effects on M. lineata ChE. No in vitro effects of cadmium on ChE activity of any of the tested species was observed. Copper had no significant in vivo effects on ChE activity, although it inhibited the ChE of both species in vitro, the IC50s being 5.87 and 12.17 mg/L for N. lapillus and M. lineata, respectively. Cadmium had no significant effects on GST activity of either species, while copper caused a significant reduction of N. lapillus GST (LOEC = 0.044 mg/L) but had no effect on M. lineata GST. Results indicate that (i) N. lapillus and M. lineata have a similar acute sensitivity to cadmium and copper; (ii) ChE and GST of these species are sensitive to cadmium (iii) ChEs of both species are inhibited by copper at concentrations in the mg/L range and therefore, its use is limited to heavily polluted sites; (iv) N. lapillus GST does not seem to be a suitable biomarker for copper, at least in the range of concentrations tested, since it was inhibited by copper, but no clear concentration-response relationship was observed.