硒是动物体必需的微量元素，但是硒含量过高或过低均可对生物体产生毒性效应. 文章阐述了硒在生物体内硒蛋白、抗氧化、免疫系统中的有益性及作用机制；总结了硒对水生生物氧化胁迫、胚胎畸形发育、母体传递等毒性效应机制；讨论了影响硒双重生物效应的因素. 通过综述近年来微量元素硒在水生生物体内（特别是鱼类）的双重生物效应，以及影响硒双重生物效应的关键因素等，进一步解析了硒在水生生物体内的累积、代谢、转化与复杂生物效应的关系，并为今后硒双重生物效应的深入研究和科学补硒提供科学依据.
Abstract: Selenium (Se) is an essential element for animals at appropriate levels, but could be toxic at both elevated and deficient levels. Firstly, the beneficial roles of Se in selenoproteins, antioxidants, immune systems were discussed in this review. Secondly, the effects and underlying mechanisms of Se in its toxicity to aquatic organisms such as oxidative stress, embryonic deformities and maternal transfer were also evaluated. Finally, the potential key factors influencing the dual effects of Se in aquatic organisms were summarized. In general, this study reviewed the dual effects of Se in aquatic organisms, and the controlling factors of these effects, especially fish. It is aimed to better understand the bioaccumulation, metabolism, biotransformation and the complex relationship between these processes and biological effects of Se in organisms. Further studies are warranted for the clearer understanding of the elusive and dual effects of Se, which can definitely provide valuable information for the proper use of Se.