Physiological and biochemical responses of the freshwater green algae Closterium ehrenbergii to the common disinfectant chlorine

Chlorine (Cl-2) is widely used as a disinfectant in water treatment plants and for cleaning swimming pools; it is finally discharged into aquatic environments, possibly causing damage to the non-target organisms in the receiving water bodies. Present study evaluated the effects of the biocide Cl-2 to the green alga Closterium ehrenbergii (C ehrenbergii). Growth rate, chlorophyll a levels, carotenoids, chlorophyll autofluorescence, and antioxidant enzymes were monitored up to 72-h after Cl-2 exposure. C ehrenbergii showed dose-dependent decrease in growth rate and cell division after exposure to Cl-2. By using cell counts, the median effective concentration (EC50)-72-h was calculated to be 0.071 mg L-1. Cl-2 significantly decreased the pigment levels and chlorophyll autofluorescence intensity, indicating that the photosystem was damaged in C ehrenbergii. In addition, it increased the production of reactive oxygen species (ROS) in the cells. This stressor significantly increased the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase, and glutathione, and affected the physiology of the cells. These results indicate that Cl-2 induces oxidative stress in the cellular metabolic process and leads to physiological and biochemical damages in the green algae. Cl-2 discharged in industrial effluents and from water treatment plants may cause harmful effects to the C ehrenbergii a common freshwater microalgae and other non-target organisms. (C) 2016 Elsevier Inc. All rights reserved.