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

该研究的总体目标是获得缺氧和温度与金属应力之间相互作用的机制理解，以便更好地评估水生系统中的金属风险。水生生物通常受到多种压力源的影响，这些压力源可能相互作用而改变生理反应。然而，现有的风险评估方案主要基于单一压力源的数据，这种方法无法考虑并发压力源的相互作用以及暴露条件下反应的变化。事实上，美国环境保护署（U.S. EPA）已经确定，对压力源之间相互作用的机制了解不足是开发有效的风险评估工具以保护水生生物的主要障碍。特别值得关注的事实是，同时发生的压力源可引起累加性或协同毒性反应，导致压力源浓度低于当前评估程序预测的环境影响。在这些压力源中，由自然现象或人类活动和全球气候变化引起的缺氧和温度波动是水生系统中常见的压力源。因此，有必要清楚地了解这些压力源的混杂效应，以便更准确地评估和预测污染物在水生系统中造成的风险。本应用旨在了解鱼类体内缺氧和温度与金属应力的相互作用。目标是：㈠阐明金属、缺氧和热应激之间相互作用的机制，以期查明不受环境溶解氧和温度波动影响的金属特有的敏感毒理学终点；㈡查明同时发生缺氧和/或温度应激时金属毒性变化的原因和机制；（iii）识别与生态风险评估中使用的毒性适应度端点相关的生化扰动。这项研究将有助于实现我的研究计划的长期目标-开发有效和科学的防御工具来监测，预测和调节金属对环境的影响。

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.