Long-Term Exposure to Hydrogen Nanobubbles Enhances Daphnia magna Resilience Against Copper Stress: Sustainable Molecular Strategies for Growth, Reproduction, and Aquatic Health

Hydrogen nanobubbles (NBs) have emerged as a novel strategy to enhance hydrogen solubility and retention in water, thus offering potential applications to aquatic ecosystems. However, their long-term biological effects and molecular mechanisms are unclear. This study provides the first comprehensive evaluation of the chronic effects of hydrogen NB water on the growth and reproduction of Daphnia magna (D. magna) under copper stress, uncovering key molecular pathways and pivotal genes. Over prolonged exposure, hydrogen NB water promoted the growth and reproduction in D. magna. Mechanistically, transcriptomic analysis revealed that hydrogen NB water promotes protein hydrolysis by upregulating carboxypeptidase A, boosting energy metabolism, and facilitating molting through the upregulation of Chitinase. In addition, hydrogen NB water attenuated retinol metabolism by upregulating retinol dehydrogenase, thereby influencing signal transduction pathways. In reproduction, hydrogen NB water significantly enhances prostaglandin synthesis by upregulating prostaglandin synthase and carbonyl reductase, improving energy homeostasis and reproductive capacity. These results not only highlight the molecular basis for the enhanced growth and reproduction of hydrogen NB water and provide a foundation for their application in improving pollutant stress in aquatic ecosystems. This study provides novel insights into the ecological role of hydrogen NB water and its implications for the sustainable management and restoration of aquatic ecosystems.