Oxidative stress response to hydrogen peroxide exposure of Mytilus galloprovincialis and Ruditapes philippinarum: Reduced embryogenesis success and altered biochemical response of sentinel marine bivalve species

The elevated concentration of hydrogen peroxide (H₂O₂) due to natural and anthropogenic causes is a significant bane to marine and coastal organisms, as it has a prolonged half-life and can inject across lipid bilayers and interfere with aquatic redox processes. The present assessment aimed to determine the acute effect of H₂O₂ on larval development of the Mediterranean mussel Mytilus galloprovincialis and to observe the oxidative stress (OS) responses, including genotoxicity and neurotoxicity in the clam Ruditapes philippinarum. Two experiments were performed, in which (a) mussel embryos were exposed to the consecutive dilution (0.0, 0.05, 0.5, 5.0, 50.0 and 500.00 μM) of H₂O₂ for 48 h and (b) adult clams were exposed to similar concentrations - of this reactive oxygen species (ROS) for 21 days. Incremental H₂O₂ significantly retarded the growth of mussel larvae; the percentage of malformed larvae increased with increasing toxicant concentration (p < 0.01, and r = 0.884). H₂O₂ also induced oxidative stress (OS) in clams, indicated by the activation/inactivation of antioxidant enzymes (GST, GPx, and GR) with a significant rise in lipid peroxidation (LPO) in the digestive gland tissues of the clams (p < 0.05). No genotoxicity or neurotoxicity on R. philippinarum were evident after chronic exposure. The battery of responses (organismal and cellular parameters) showed embryotoxicity and sublethal effects on bivalves, which confirmed their suitability for assessing the effect of H₂O₂ mediated OS responses in the marine environment.