Biological effects of TiO 2 and CeO 2 nanoparticles on the growth, photosynthetic activity, and cellular components of a marine diatom Phaeodactylum tricornutum.

It is very important to have a good understanding of the biological effects of nanoparticles (NPs) on marine diatoms. In this study, the physiological and biochemical responses of a marine diatom Phaeodactylum tricornutum to titanium dioxide NPs (nano-TiO2 ) and cerium oxide NPs (nano-CeO2 ) were compared and evaluated using 96h growth tests in a batch-culture system. At 96h of exposure, the growth inhibition rate (IR, %) of P. tricornutum increased from 5.46 to 27.31% with increasing nano-TiO2 concentrations from 2.5 to 40mgL-1 . The maximum IR of 49.59% occurred in 40mgL-1 nano-TiO2 treatments at 48h of exposure. Growth of the diatom was increased in low nano-CeO2 treatments (≤5mgL-1 ), but was inhibited in high nano-CeO2 treatments (≥10mgL-1 ). Large aggregates of NPs were attached to the cells of P. tricornutum in 20 and 40mgL-1 nano-TiO2 and nano-CeO2 treatments. In addition, the effective quantum yields (ΦPSII ) of P. tricornutum in 40mgL-1 nano-TiO2 and nano-CeO2 treatments were 83.33 and 71.13% of that in the controls at 96h of exposure, respectively. Compared with that of the controls at 96h of exposure, chlorophyll a content, soluble sugar content, malondialdehyde (MDA) content, SOD and POD activities of P. tricornutum in 40mgL-1 nano-TiO2 and nano-CeO2 treatments increased by 57.56, 142.97, 373.25, 698.76, 204.85% and 21.43, 89.41, 194.97, 340.05, 502.86%, while soluble protein content decreased by 70.38 and 28.64%, respectively. These findings will be helpful to understand the effect mechanisms of NPs on marine organisms.