Combined effects of graphene oxide and Cd on the photosynthetic capacity and survival of Microcystis aeruginosa

In this work, the combined effects of graphene oxide (GO) and Cd2+ solution on Microcystis aeruginosa were investigated. Chlorophyll fluorescence parameters were measured by a pulse-amplitude modulated fluorometer. GO at low concentrations exhibited no significant toxicity. The presence of GO at low concentrations significantly enhanced Cd2+ toxicity as the 96 h half maximal effective concentration of the Cd2+ reduced from 0.51 +/- 0.01 to 0.474 +/- 0.01 mg/L. However, concentrations of GO above 5mg/L did not significantly increase the toxicity of the Cd2+/GO system. Observations through scanning and transmission electron microscopy revealed that GO, with Cd2+, easily attached to and entered into the algae. Reactive oxygen species and malondialdehyde were measured to explain the toxicity mechanism. The photosynthetic parameters were useful in measuring the combined toxicity of the nanoparticles and heavy metals. (C) 2015 Elsevier B.V. All rights reserved.