Toxicological effects of phenol on four marine microalgae

The toxic effects of phenol on four marine microalgae (Dtmaliella sauna, Platymonas subcordiformis, Phaeodactylum tricomutum Bohlin, and Skeletonema costatum) were evaluated. The 96 h EC50 values were 72.29, 92.97, 27.32, and 27.32 mg L-1, respectively, which were lower than those values of freshwater microalgae reported in the literature. During a 96-h exposure to a sub-lethal concentration of phenol (1/2 96 h EC50) with green alga (D. sauna) and diatom (S. costatum), reactive oxygen species (ROS) accumulation, and chlorophyll a (Chl a) content decrease were simultaneously observed in diatom cells after 48 h treatment. On the contrary, other chlorophylls in both algae were unaffected. Under transmission electron microscopy (TEM), the phenol-induced ultrastructure alterations included disappearance, or shrinkage, of nucleolus and enlargement of vacuoles, which may result in programmed cell death (PCD). The increase in number of lipid droplets may be related to phenol detoxification. These results indicate that the sensitivity of marine microalgae to phenol was dependent on some biotic factors such as cell size, ROS production, and phenol degradation ability in algal cells.