Comprehensive toxicity assessment of selected pharmaceuticals (ciprofloxacin, amoxicillin, and levofloxacin) on freshwater microalgae Scenedesmus obliquus: effect of media composition

Abstract

Antibiotics are widely used in health care to treat various infections. Excessive use and poor waste management make antibiotics a serious threat to aquatic ecosystems. Most of the ecotoxicological assessments on freshwater microalgae are evaluated in the defined culture medium, which lacks environmental relevance. Hence, this study aimed to evaluate the toxicity of amoxicillin, ciprofloxacin, and levofloxacin on the freshwater microalga Scenedesmus obliquus in both lake water medium (LWM) and Blue green-11 medium (BG-11 M). Results indicated that levofloxacin exhibited the highest toxicity, followed by amoxicillin and ciprofloxacin in both LWM and BG-11 M. Pearson correlation and cluster heat map analyses revealed that oxidative stress generation was directly linked to reduced photosynthetic activity and cell viability. These findings suggest toxicity assessments conducted in defined culture media may modulate the toxicity levels compared to environmentally relevant media, like lake water.