Potential toxicity of ionic liquid ([Cmim]BF) on the growth and biochemical characteristics of a marine diatom Phaeodactylum tricornutum.

Recently, some researchers have pointed out that the threats of ionic liquids (ILs) to aquatic environment cannot be ignored. Thus, this study investigated the potential toxicity of 1-dodecyl-3-methylimidazolium tetrafluoroborate ([Cmim]BF) on a marine diatom Phaeodactylum tricornutum at population, biochemical and physiological levels using 96h growth tests with a batch-culture system. Results showed that [Cmim]BF was very stable in aquatic environment during 96h of exposure. The growth of P. tricornutum was significantly inhibited by [Cmim]BF with 24, 48, 72 and 96h EC values of 0.63, 0.61, 0.68 and 0.72mgL, respectively. Although there were no significant differences between the controls and treatments with 0.1 and 0.5mgL [Cmim]BF, the effective quantum yields (Φ) of the diatom in 1, 2.5, 5 and 10mgL [Cmim]BF treatments were 61.48, 17.04, 2.96 and 0.74% of that in the controls at 96h of exposure, respectively. Chl a content of the diatom was decreased by 34.86, 47.79, 49.81, 59.21, 79.82 and 86.98% compared with that of the controls at 96h of exposure in 0.1, 0.5, 1, 2.5, 5 and 10mgL [Cmim]BF treatments, respectively. Relative to the controls, soluble sugar content, reactive oxygen species (ROS) level, malondialdehyde (MDA) content, superoxide dismutase (SOD) and peroxidase (POD) activities of the diatom increased with increasing [Cmim]BF concentrations at 96h of exposure, and reached their maxima (1.46μg10cell, 7.48FU10cell, 3.35nmol10cell, 33.41 and 7.23Umg proteins, respectively) in 5mgL [Cmim]BF treatments. While the maximum soluble protein content (1.56μg10cell) of the diatom was obtained in 0.5mgL [Cmim]BF treatments, and then decreased with increasing [Cmim]BF concentrations from 0.5 to 10mgL. These findings provide strong evidence for the potential toxicity of ILs to marine diatoms.