Microalgal Exposure to Human Antibiotics Triggers Similarities in Growth and Photosynthetic Responses

Abstract

The discharge of pharmaceuticals via wastewater into the environment is a great concern due to the constant threat posed to photosynthetic organisms since they are vital for the sustenance of the aquatic food web. To compare the photosynthetic and growth responses of green algae to human antibiotics, Raphidocelis subcapitata and Chlorella vulgaris were exposed to erythromycin and sulfamethoxazole for 96 h. A much higher sensitivity was shown by Raphidocelis to the antibiotics. Although erythromycin was more acutely toxic to photosynthesis (EC 50 , 24.6 µg/L; EC 10 , 14.6 µg/L) than growth (EC 50 , 160 µg/L; EC 10 , 27 µg/L) in Raphidocelis, chronic effects in terms of EC 10 were alike. Interestingly, sulfamethoxazole exhibited similar toxicity towards growth and photosynthesis with the acute and chronic toxicity parameters for growth (EC 50 , >2000 µg/L; EC 10 , 260 µg/L for Raphidocelis; and EC 50 , 47,900 µg/L; EC 10 , 19,100 µg/L for Chlorella) in consonance with those of photosynthesis (EC 50 , >2000 µg/L; EC 10 , 340 µg/L for Raphidocelis; and EC 50 , 47,500 µg/L; EC 10 , 13,400 µg/L for Chlorella). Growth and photosynthesis in Raphidocelis were strongly inhibited in this study at environmentally relevant concentrations of erythromycin. The findings from this study demonstrated that photosynthetic yield was a reliable indicator of sulfamethoxazole and erythromycin effects and thus, may be useful as an alternative approach to growth in assessing chronic toxicity in antibiotics.