Biological Toxicity of Fresh and Rotten Algae on Freshwater Fish: LC50, Organ Damage and Antioxidant Response

Abstract In recent decades, harmful algal blooms (HABs) induced by eutrophication have caused organisms in freshwater ecosystems to become surrounded by toxic cells and dissolved toxins. In this study, the toxic effects of fresh algae solution (FAS) and rotten algae solution (RAS) were investigated. The results showed that the composition of RAS was predominantly organic acids, ketones, polypeptides, esters, phenols, amino acids and intermediate metabolic products. The safety concentrations (SCs) of FAS to Carassius auratus, Ctenopharyngodon idellus and Hypophthalmichthys molitrix were 1.92 × 1010 cells/L, 1.58 × 1011 cells/L and 1.30 × 1011 cells/L, respectively. The SCs of the RAS were significantly lower than those of the FAS (p