Algal organic matter accelerates the photodegradation of tetracycline: Mechanisms, degradation pathways and product toxicity

•AOM-mediated indirect photolysis is much faster than direct photolysis of tetracycline.•EOM is more effective than IOM in promoting tetracycline photolysis.•Tryptophan and protein-like organics in AOM participate in the photodegradation of tetracycline.•Triplet-state AOM contributes the most to tetracycline degradation, followed by ⋅OH and 1O2.•New photodegradation pathways and product toxicity of tetracycline mediated by AOM are proposed.