Interactive effects of ocean acidification and benzophenone-3 on mussel physiology: A biomarker-based approach

Benzophenone-3 (BP3), a widely used ultraviolet (UV) filter in personal care products and industrial applications, is an emerging concern in aquatic ecosystems due to its lipophilicity, bioaccumulation potential, and toxicity to marine biota. Its occurrence in marine environments coincides with ocean acidification driven by rising atmospheric CO₂ emissions, which disrupts the bicarbonate buffer system and reduces pH. This study investigated the acute effects (96 h exposure) of BP3 (at realistic concentrations of 0.2 and 2 μg/L) under 3 pH conditions (8.1- the current South Atlantic condition- and 7.6 and 7.3 as projected acidification scenarios for 2100 and 2300, respectively) in the brown mussel Perna perna. The effects were investigated through analysis of hemocyte viability and biomarkers related to detoxification (glutathione S-transferase, glutathione, glutamate cysteine ligase, and reduced glutathione), oxidative stress (antioxidant capacity against peroxyl radicals and lipid peroxidation), and biomineralization (carbonic anhydrase and Ca²⁺ATPase), measured in the gills, digestive gland, and mantle. Despite BP3-induced activation of glutathione-related detoxification pathways, as evidenced by increased GSH levels and GST activity, particularly in the gills, hemocyte viability decreased after BP3 exposure, with the greatest reduction at pH 7.3. Lipid peroxidation (LPO) also increased in the gills and digestive gland under acidified conditions, with the magnitude of the response varying according to BP3 concentration. CA and Ca²⁺ATPase activities were more strongly influenced by acidification than by BP3 exposure, although their responses were tissue-specific and, in some cases, modulated by BP3 exposure. Multivariate analyses identified pH as the primary driver of biomarker responses.