Elevated Temperature as a Dominant Driver to Aggravate Cadmium Toxicity: Investigations through Toxicokinetics and Omics

Despite the great interest in the consequences of global change stressors on marine organisms, their interactive effects on cadmium (Cd) bioaccumulation/biotoxicity are very poorly explored, particularly in combination with the toxicokinetic model and molecular mechanism. According to the projections for 2100, this study investigated the impact of elevated pCO2 and increased temperature (isolated or joint) on Cd uptake dynamics and transcriptomic response in the marine copepod Tigriopus japonicus. Toxicokinetic results showed significantly higher Cd uptake in copepods under increased temperature and its combination with elevated pCO2 relative to the ambient condition, linking to enhanced Cd bioaccumulation. Transcriptome analysis revealed that, under increased temperature and its combination with elevated pCO2, up-regulated expression of Cd uptake-related genes but down-regulation of Cd exclusion-related genes might cause increased cellular Cd level, which not only activated detoxification and stress response but also induced oxidative stress and concomitant apoptosis, demonstrating aggravated Cd biotoxicity. However, these were less pronouncedly affected by elevated pCO2 exposure. Therefore, temperature seems to be a primary factor in increasing Cd accumulation and its toxicity in the future ocean. Our findings suggest that we should refocus the interactive effects between climate change stressors and Cd pollution, especially considering temperature as a dominant driver. Cadmium (Cd), a representative of metal contaminants, poses a great threat to the marine ecosystem. Cd pollution in the context of human-induced climate change (e.g., increased temperature and high pCO2) can have stronger negative impacts on marine biota. This study integrating toxicokinetics and omics approaches revealed that climate change stressors can aggravate Cd uptake and accumulation in marine organisms, rendering Cd pollution exhibiting higher risk, and also providing the potential mechanism related. In particular, increased temperature plays a dominant role. This study has given new insights into the complex interaction between climate change stressors and metal pollution in the marine ecosystem.