Predicted Near-Future Oceanic Warming Enhances Mercury Toxicity in Marine Copepods

The effects of acute mercury exposure (118 µg/L) on the marine copepod Tigriopus japonicus were examined at 22 and 25 °C for 24 h and compared with controls. Mercury accumulation and seven genes related to antioxidant/stress responses were analyzed after exposure. The 24-h LC 50 value decreased in the warmer environment and mercury accumulation was elevated. Under both temperatures, mercury significantly affected the expression of all analyzed genes and probably caused oxidative stress. Intriguingly, at the same mercury concentration, most genes were upregulated at the higher relative to the lower temperature, and the copepods likely initiated more compensatory reactions to counteract increased mercury toxicity associated with the warmer temperature. Overall, this study suggests a molecular mechanism by which marine copepods could respond to future oceanic warming and mercury pollution.