Toxicity of Zinc Oxide Nanoparticles on Marine Microalgae Possessing Different Shapes and Surface Structures

To investigate the toxicity of ZnO nanoparticles (NPs) on microalgae, Bacillariophyta (Skeletonema costatum and Phaeodactylum tricomutum) and Chlorophyta (Dunaliella salina and Platymonas subcordiforus) were cultivated in f/2 medium under uniform culture conditions with different concentrations of ZnO NPs. Growth inhibition ratio and the 50% effective concentration were used as two toxicity parameters for comparing toxicities on different microalgae. Dose–response curves were built to show different trends in toxicities of ZnO NPs on the four microalgae. The sensitivity rank of the algae to toxicity of ZnO NPs was S. costatum>D. salina>P. tricomutum>P. subcordiforus. Adsorption of ZnO NPs on S. costatum and D. salina was clearly observed in scanning electron microscope images. In contrast, no adsorption of ZnO NPs was found on surfaces of P. tricomutum and P. subcordiforus. Shapes and surface structures of the microalgae resulted in different adsorption phenomena, which had an influence on interactions between NPs and microalgae. This study helps to explain the different toxicities of ZnO NPs on the four microalgae, which could contribute to further explore toxic mechanisms of NPs.