Physiological and Molecular Responses of a Marine Copepod Under Multigenerational Exposure to Coastal Warming and Mercury at an Environmentally Realistic Concentration

In this work, we investigated how a warmer temperature (26 °C) and mercury pollution (1 μg/L) affect the marine copepod Tigriopus japonicus across three generations (F0-F2). Several phenotypic traits and mercury accumulation were measured in each generation, and the proteome of the F2 copepods was analyzed. The results show that a warmer temperature and mercury exposure significantly affected the phenotypic traits. Combined exposure significantly increased mercury bioaccumulation and consequently potentiated its toxicity in each generation relative to mercury treatment alone. The proteomic analysis demonstrated that the warmer temperature caused the copepods to upregulate the determination of adult lifespan pathway to maintain rapid growth but at the cost of an organism’s fitness, as exemplified by the male-biased sex ratio and compromised reproduction. Mercury pollution had several toxic effects, e.g., energy depletion and reduced defense performance, that ultimately translated to decreased reproduction. Importantly, the warmer temperature aggravated mercury toxicity, mainly by disturbing energy metabolism and impairing detoxification systems, which were linked to depressed feeding and reproduction in T. japonicus. Our study provides a mechanistic, multigenerational understanding of the response of T. japonicus to coastal warming and mercury pollution, with emphasis on enhanced mercury toxicity in marine copepods under warmer conditions.