In this study, the effect of textile dye (Optilan Red) toward microalgae Chlorella vulgaris was monitored for a period of 96 hours. The parameters such as specific growth rate (SGR), EC50, protein, chlorophyll, carotenoid and elemental composition of the microalgae were recorded. Results showed that SGR for C. vulgaris decreased with increase in concentration of dye and a significant decrease was noticed upto 20 ppm however, further increase in concentration showed no growth of the organism. EC50 for Optilan Red was found to be ppm. | Evaluation of toxicity of a textile dye Optilan Red towards a green microalga Chlorella vulgaris