Differential mercury tolerance in a planktonic copepod under different climate scenarios: A multigeneration...

Anthropogenically induced climate change and mercury (Hg) pollution are increasingly threatening marine ecosystems. However, whether and how different temporal scenarios of acidification and warming (AW) affect Hg toxicity in organisms remain poorly understood. Using a multigenerational experiment (F1-F4) with the planktonic copepod Pseudodiaptomus annandalei, we investigated how offspring, ancestral, and persistent AW scenarios affect toxicity from 1 μg/L Hg. We found that offspring AW mitigated Hg toxicity in copepods, whereas ancestral/persistent AW aggravated Hg toxic effects. Transcriptomic analysis of F4 copepods revealed that offspring AW activated Hg efflux and energy production, facilitating a compensatory response to Hg exposure. In contrast, under ancestral AW and persistent AW, key cellular defenses, particularly antioxidant capacity, Hg detoxification, and immune defense, were inhibited. This suppression was more pronounced under persistent AW scenario, linking to the compromised development and reproduction. Our findings demonstrate that the temporal scenarios of climate change stressors critically modulate Hg toxicity, providing more realistic inferences for assessing the combined ecological risks of climate change and Hg pollution in marine ecosystems.