Combined effects of Benzotriazole Ultraviolet Stabilizers and Cadmium on physiological performance of marine dinoflagellate Akashiwo sanguinea

As emerging contaminants, benzotriazole ultraviolet stabilizers (BUVSs) have been frequently detected in aquatic environments, which usually co-occur with heavy metals and cause complex toxicity to aquatic organisms. However, the specific role of BUVSs in the combined toxicity remains poorly understood. Herein, a harmful marine dinoflagellate Akashiwo sanguinea was used to explore the individual and combined toxicities of UV-234 and cadmium (Cd 2+ ). Exposure to UV-234 at an environmental concentration (10 μg L −1 ) slightly inhibited algal growth ( P > 0.05). Individual exposure to both low (1.77 mg L −1 ) and high (5.30 mg L −1 ) concentrations of Cd 2+ significantly impaired algal photosynthesis by altering photosynthetic pigments, disrupting energy absorption, dissipation and trapping, reaction center activation, and electron transport, thereby inducing oxidative stress, and up-regulated pyruvate metabolism and the tricarboxylic acid cycle. Notably, co-exposure with UV-234 mitigated the toxic effects induced by Cd 2+ , and caused weaker inhibition of algal growth via inducing less substantial oxidative damage. These findings highlight the significant influence of UV-234 and Cd 2+ co-exposure on marine dinoflagellates, providing new insights into the joint toxicity mechanisms and a scientific basis for environmental risk assessment of emerging BUVSs.