Lithium with environmentally relevant concentrations interferes with mitochondrial function, antioxidant response, and autophagy processes in Daphnia magna, leading to changes in life-history traits and behavior.

With the increasing production and use of lithium-based products, concerns over lithium pollution in aquatic ecosystems are increasing, whereas research on its toxicity mechanisms in aquatic organisms remains limited. The main objective of the present study was to explore the effects of environmentally relevant concentrations of lithium exposure on the life-history strategy, behavior, antioxidant system, and autophagy process of Daphnia magna. Acute (24-96 h) and chronic (21 days) exposure experiments under three lithium treatments (low: 8.34 μg/L, medium: 83.44 μg/L, and high: 834.41 μg/L) were conducted. The results indicated that exposure to medium and high lithium concentrations led to eye and tail deformities in D. magna. Furthermore, developmental and reproductive parameters such as body length, total neonates per female, and average neonates per time were negatively influenced. Lithium also interfered with energy metabolism to cause the decreasing swimming speed and the reduction in the swimming range. In addition, lithium exposure affected the expression of gsk-3β, further disrupting the dynamic balance of mitochondrial fission, fusion, and regeneration, which caused ROS accumulation and induced oxidative stress. D. magna attenuated the stress by activating the FoxO/SESN and Nrf2/Keap1 pathways, synergistically enhancing downstream antioxidant enzymes expression. Concurrently, D. magna also mitigated oxidative stress and mitochondrial damage by promoting autophagy and inhibiting apoptosis. In summary, lithium harmed the physiological and biochemical functions of D. magna through multiple mechanisms, suggesting that environmental lithium pollution may pose a potential threat to aquatic organisms.