Toxicity of engineered copper (Cu(0)) nanoparticles to the green alga Chlamydomonas reinhardtii

Environmental context Engineered copper nanoparticles are presently under development for various uses and may thus be finally released into the aquatic environment. Copper is well known to be both an essential and a toxic element for aquatic organisms. Here, we investigate the toxicity of copper nanoparticles to a green alga and compare it with the toxicity of dissolved copper. Abstract The toxicity of carbon-coated copper nanoparticles (CuNPs) to the unicellular green alga Chlamydomonas reinhardtii was investigated and compared with effects of dissolved Cu2+. The CuNPs with an original size of 6-7nm rapidly agglomerated in the medium to average particle sizes of 140-200nm. Dissolved Cu from CuNPs increased over 2h to 1-2% of total Cu. The photosynthetic yield of C. reinhardtii strongly decreased after exposure for 1 or 2h to dissolved Cu-II in the concentration range 0.1-10M, whereas this decrease occurred in the total Cu concentration range 1-100M after exposure to CuNPs. Effects of CuNPs were compared with those of dissolved Cu-II on the basis of dissolution experiments. CuNP effects on photosynthetic yield were similar or somewhat stronger for the same dissolved Cu2+ concentration. Addition of EDTA as a strong ligand for Cu-II suppressed the toxicity of dissolved Cu-II and of CuNPs. These results thus indicate effects on the algae are mostly from free Cu2+.