Mechanisms of interactions of hypoxia and temperature with metal stress in fish

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The overall goal of the proposed research is to gain mechanistic understanding of the interactions between hypoxia and temperature with metals stress for better assessment of metals risk in aquatic systems. Aquatic organisms are generally impacted by multiple stressors that may interact with each other to alter physiological responses. However, extant risk assessment protocols are based largely on data from single stressors, an approach that fails to account for interactive effects of concurrent stressors and variation of responses with conditions of exposure. Indeed, inadequate understanding of the mechanisms of interactions between stressors has been identified by the United States Environmental Protection Agency (U.S. EPA) as a major obstacle to the development of effective risk assessment tools to protect aquatic life. Of particular concern is the fact that co-occurring stressors can cause additive or synergistic toxicological responses resulting in environmental impacts at lower stressor concentrations than predicted by current assessment procedures. Among these stressors, hypoxia and temperature fluctuations resulting from natural phenomena or human activities and global climate change are commonly encountered in aquatic systems. A clear understanding of the confounding effects of these stressors is therefore necessary for more accurate assessment and prediction of the risk posed by pollutants in aquatic systems. This application seeks to understand interactions of hypoxia and temperature with metals stress in fish. The objectives are: (i) to elucidate the mechanisms of interactions of metals, hypoxia and thermal stress with a view to identifying sensitive metal-specific toxicological endpoints that are immune to fluctuations in environmental dissolved oxygen and temperature, (ii) to identify the causes and mechanisms of altered metals toxicity during concurrent hypoxia and/or temperature stress, and (iii) to identify biochemical perturbations that correlate with fitness endpoints of toxicity used in ecological risk assessment. The proposed research will contribute to the realization of the long term goal of my research program- the development of effective and scientifically defensible tools to monitor, predict and regulate environmental impacts of metals.