A comparison of the effects of copper nanoparticles and copper sulfate on Phaeodactylum tricornutum physiology and transcription

Copper nanoparticles (CuNPs) have been used in a broad range of applications. However, they are inevitably released into the marine environment, making it necessary to evaluate their potential effects on marine phytoplankton. In this study, the short-term (96 h) effects of CuNPs and CuSO4 on Phacodactylum tricornutum growth, photosynthesis, reactive oxygen species production and transcription were assessed. It was found that high concentrations (40 Ad) of CuNPs and CuSO4 significantly inhibited the growth, photosynthesis and induced oxidative stress of P. tricornutum, while lower concentrations caused a hormetic response as indicated by a slight stimulation in algal growth. The high percentage of dissolved Cu (78-100%) in culture medium suggested that the dissolved Cu was the main driver of toxicity during CuNPs treatment. The algal cells upregulated electron transport chain-related genes to produce more energy and restore photosynthesis after 96 h of treatment with CuNPs and CuSO4. This study delineates the cellular mechanism behind the toxicity of CuNPs and CuSO4 on marine diatoms.