Comp Biochem Physiol Part D Genomics Proteomics 2026 May 12;59:101865. doi: 10.1016/j.cbd.2026.101865.

Ionomic, metabolomic, and enzymatic responses of the sea cucumber Apostichopus japonicus to single and combined salinity and metal stress.

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Desalination brine discharge poses emerging threats to benthic marine organisms through combined salinity stress and metal contamination. This study investigated the individual and combined effects of salinity (35 ppt) and metal exposure (Cu, Fe, and Cd) on the sea cucumber Apostichopus japonicus by integrating ionomics, enzymatic biomarkers, and LC-MS/MS-based metabolomics. After 16 days of exposure, only Cd and Cu significantly accumulated in body wall tissues. Combined high salinity and metals contributed to a slight increase in Fe accumulation and a decrease in Cu accumulation. Metal exposure disrupted the balance of metal elements (e.g., Mn, Zn, Co, Ni), with interactive effects modulated by salinity. Antioxidants and immune-related enzymes (SOD, CAT, ACP, ALP, Na+/K+-ATPase) responded distinctly to metal and salinity stress, with salinity often dominating the combined stress response. Metabolomic profiling revealed that Cd and Cu under ambient salinity induced widespread metabolic perturbations, altering metabolites related to lipid metabolism, glutathione metabolism, and saponin biosynthesis. Notably, high salinity (35 ppt) alleviated some metal-specific metabolic effects, while salinity alone caused significant downregulation of bioactive saponins and flavonoids. These findings demonstrate that salinity modulates metal toxicity in sea cucumbers, with potential consequences for immune function, oxidative defense, and nutritional value. This study provides novel insights into the ecological risks of desalination brine discharge on benthic ecosystems.

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