Chlorination-induced cellular damage and recovery in marine microalga, Chlorella salina

Power plants employ chlorination for controlling biofouling in the cooling water system. Phytoplankton drawn into the cooling water system could be impacted by chemical stress induced by the oxidizing biocide. It is likely that microalgae, being sensitive to chlorine, could suffer damage to their cellular structure and function. In this study, we present data on the effect of in-use concentrations of chlorine on the unicellular microalga, Chlorella salina. Chlorophyll autofluorescence was measured in terms of mean fluorescence intensity per cell for rapid assessment of toxicity. Viability of the cells exposed to chlorine was determined by fluorescein diacetate staining. Functionality of the photosynthetic machinery was assessed by gross primary productivity. Results from the study, which combined confocal laser scanning microscopy with image analysis, showed a significant dose-dependant reduction in chlorophyll autofluorescence, esterase activity and gross primary productivity in chlorine-treated cells. Interestingly, the cells injured by chlorination could not recover in terms of autofluorescence, esterase activity or productivity even after 18 h incubation in healthy media. Among the test points evaluated, esterase activity appeared to be sensitive for determining the chlorination-induced impact. Our results demonstrate that low-dose chlorination causes significant decrease in chlorophyll autofluorescence, intracellular esterase activity and primary productivity in Chlorella cells.