Oxidative Stress Responses and Recovery of Marine Medaka (Oryzias melastigma) in Early-Life Stages After Acute Exposure to Crude Oil

Oil spills pose a significant threat to marine ecosystems, with potentially adverse impacts on fish in early-life stages. Despite numerous studies reporting the developmental toxicity of oil exposure, knowledge about the recovery capacity of fish after oil exposure remains limited. Therefore, this study investigated the effects of water-accommodated fractions (WAFs) of Oman crude oil on the development and oxidative stress of marine medaka (Oryzias melastigma) embryos during a 7-day acute exposure period followed by a 14-day recovery period in clean seawater. Results revealed that WAF exposure caused concentration-dependent developmental toxicity gradually becoming apparent during the recovery period, including reduced survival and hatching rates, and increased morphological abnormalities. During the exposure period, low WAF concentrations triggered antioxidant responses (elevated SOD and CAT activities, and GSH content), while higher concentrations caused a concentration-dependent increase in lipid peroxidation (elevated MDA content). Differently, during the recovery period, all groups showed impaired antioxidant capacity (decreased SOD, CAT, GSH) and immune function (reduced AKP activity). Principal component analysis revealed strong correlations between survival, oxidative stress markers, and developmental toxicity. These findings could provide valuable insights into the recovery capacity of fish exposed to crude oil and give references for assessing the recovery potential of marine ecosystems after oil spills.